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You can use several words in query to find by all of them at the same time. In addition, if you are lucky search understands word forms and some synonyms. It supports search by title and author. Examples:
305— search for 305, most probably it will find blogs about the Round 305andrew stankevich contests— search for words "andrew", "stankevich" and "contests" at the same timeuser:mikemirzayanov title:testlib— search containing "testlib" in title by MikeMirzayanov"vk cup"— use quotes to find phrase as istitle:educational— search in title
Results
1.
research
Last visit:
4 years ago
Registered:
4 years ago
2.
New: Diagnostics of Solutions in C++ <img src = "/predownloaded/b5/d2/b5d246ffc32dfe82c3cbac77d1898c5fcb62fa57.jpg" style = "float: right; margin: 0 1em 1em 1em;"/>
Hello!
I am pleased to report that two rounds of Codeforces have gone quite well in terms of the work of Codeforces, I am very glad about it. These <s>days</s> nights I spent in a profiler, fixing the code, researching the settings of MariaDB.
In addition, I managed to allocate several hours on Sunday (to be honest, until Monday morning) to finish the long-planned innovation.
Meet, diagnostics of solutions in C++!
Many Codeforces visitors are already tired of the questions of less experienced participants: "Why does my solution not work on some test on the Codeforces servers, if I locally launch it and it works correctly? You have the wrong compiler/servers!" In 99% of cases this is an example of <a href ="https://en.wikipedia.org/wiki/Undefined_behavior">undefined behavior</a> in a program. In other words, the program contains mistakes that, du...
3.
Codeforces: Results of 2019 <a style="float:right; display: inline-block; margin:0 1em 1em 2em; max-width: 60%;" href="https://codeforces.com/10years"/>
<img style="max-width:100%" src="https://assets.codeforces.com/images/codeforces-10-years-300.png"/>
</a>
Hi Codeforces!
The platform recently turned 10 years old. We accept your congratulations at <a href="https://codeforces.com/10years">https://codeforces.com/10years</a>.
Please review the progress in 2019 and support the anniversary crowdfunding campaign. Your donation will be a contribution to the future of Codeforces, will
help its development and work. We need resources to continue to host rounds, not to stop developing,
to innovate and to maintain the existing infrastructure.
In 2019, together with numerous writers the coordinators worked on problems: [user:KAN,2020-02-06], [user:300iq,2020-02-06], [user:cdkrot,2020-02-06], [user:arsijo,2020-02-06] and recently joined [user:isaf27,2020-02-06]. And this year,
rounds coordinated by other exper...
contests * **Huawei** — research competition (marathon) with elements of
machine learning, ; research competition (marathon) with elements of machine learning *
**Forethought**, Forethought
4.
[Repost] "Justice may be delayed, but it cannot be absent": New Evidence on
NXIST's Cheating Scandal
[Repost] "Justice may be delayed, but it cannot be absent": New Evidence on NXIST's Cheating Scandal _Original post: [「正义可以迟来但不能缺席」：关于 NXIST 的一些新证据](https://zhuanlan.zhihu.com/p/620297880)_
_Translated by GPT-4 with some adjustment. Please inform me if there are any mistakes._
_All links to the invalid repository have been redirected to the backup repository._
**This article provides a logically complete set of evidence, which does not involve any non-public internet resources, regarding the "suspected cheating" incident involving the ICPC Yinchuan Station and ICPC Shenyang Station in 2021. By discovering the suspected GitHub account ([NaokiLH](https://github.com/NaokiLH), renamed to https://github.com/brokenTarget) of a team member from Ningxia Institute of Science and Technology (NXIST) TS 1 team, Lan Hao, two years ago, and by mining and analyzing the commit records of his algorithm competition repo, we have obtained direct evidence that at least 4 questions from the 2021 Yinchuan regional contest set and at least 6 questions (including scrapped questions) from the 2021 Sh...
solutions or standard inputs and outputs. May 10, NaokiLH, through research or
seeking help from, From May 21 to June 11, NaokiLH obtained the codes for the mentioned problems
throughresearch, May 10, NaokiLH, through research or seeking help from others, writes the code
for Problems B, G
5.
[Tutorial] GCC Optimization Pragmas ## Introduction
A while ago [user:ToxicPie9,2021-10-27] and I made and posted this meme:
To my surprise, many people are quite confused about it. In fact, I realized there are a lot of misconceptions about pragmas. Most C++ users on Codeforces put a few lines of pragmas at the start of every submission. However, I believe many of them don't fully understand what they're doing or how pragmas work; the only thing people seem to think is that "add pragmas -> code go brr".
Pragmas are a form of the dark arts that are feared and used, both correctly and incorrectly, by lots of competitive programmers. They are widely believed to make your code much faster, but sometimes may lead to slowdowns and even runtime errors on certain platforms. In this blog, I will explain the effects of `#pragma GCC optimize` and `#pragma GCC target`, how they work, and how you should and shouldn't us...
6.
Codeforces Global Rounds Hello!
It is always satisfying and important for me when former contest participants offer their help to the community and support the development of programming competitions. And now I am in a hurry to share the news that thanks to the support of <a href="https://www.xtxmarkets.com/">XTX Markets</a> and the personal participation of Yuri Bedny and Alexander Gerko, we are launching a new line of Codeforces Global Rounds. Hooray!
<img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Like many of you, I had never heard of <a href="https://www.xtxmarkets.com/">XTX Markets</a> before but it is one of the largest quantitative-driven electronic liquidity providers in the world. I understand little about the financial sector, but with their 34,148 cores and 42 petabytes of usable storage in their research cluster, XTX’s rapid growth and strong market share globally speak for themselves.
So, in 2019, w...
storage in their research cluster, XTX’s rapid growth and strong market share
globally speak for, the financial sector, but with their 34,148 cores and 42 petabytes of usable
storage in theirresearch
7.
I might get stigmatized for this, but here it goes Recently, Moscow Fall Workshops has taken place (it ended about one week ago), and I wanted to address some issues that came into my mind during that period. As you might notice, it took me some time to build the courage and get in the right mindset to write about this.
First of all, I want to say that I am a huge supporter of programming camps and, in general, initiatives to enhance the joy of doing competitive programming and I respect the efforts of building communities around CP. I have always had a kind of excitement when thinking about participating in programming camps (Petrozavodsk, Moscow Workshops, etc.) and their “hardcore” style with lots of contests. I therefore appreciate the immense efforts of organizers, problem setters, and testers, when preparing this camp.
### Main point
Coming towards the main point of the blog, I felt that the last programming camp was a bit… underwhelming. Moreover, I’m having a hard time trying to justify the costs of doing such a camp,...
an already-solved problem during one of the contests, I did some quick research
and found that most, quick research and found that most of the contests consisted in problems that
were taken from past
8.
[Tutorial] How to learn better, and what most people don't get about learning **Disclaimer:** I am not an expert in the field of the psychology of learning and problem-solving, so take the following with a grain of salt. There is not much "scientific" evidence for this blog, and the following is validated by personal experience and the experiences of people I know (who fall everywhere on the "success" spectrum — from greys to reds in competitive programming, from beginners in math to IMO gold medalists, and from people with zero research experience to people with monumental publications for their own fields). This blog only covers one possible way of thinking about knowledge organization and retrieval that I have been using for the past decade or so, but there definitely will be other models that might work even better. Even though I just have a few courses worth of formal psychology experience, I still think the content of this blog should be relevant to people involved with problem-solving.
I hope this helps both students (to make their learning effic...
beginners in math to IMO gold medalists, and from people with zero research
experience to people with, original research and leads to good problem-setting.
9.
A simple introduction to "Segment tree beats" Hi, I’d like to introduce a simple trick about segment tree in this blog as I promised in [this comment](http://codeforces.com/blog/entry/54750?#comment-387957). Sorry for the long delay, as a sophomore in Peking University, I've just finished a tired semester and a painful final exam. And now I finally have enough time to do a simple introduction to this interesting algorithm.
It may be a huge project for me since my English is not good. I think I will finish this blog in several steps and I will try to finish it as soon as possible :)
In China, all of the 15 candidates for the Chinese National Team are asked to write a simple research report about algorithms in informatics Olympiad, and the score will be counted in the final selection. There are many interesting ideas and algorithms in these reports. And I find that some of them are quite new for competitors in CF although they are well known in China from the final standings of some recent contests. For example, In the last co...
National Team are asked to write a simple research report about algorithms in
informatics Olympiad, research report about algorithms in informatics Olympiad, and the score will be
counted in the final
10.
How to come up with the solutions: techniques As I work with students I often face the situation when if a problem doesn't seem clear to a student at the first sight, it makes them unable to solve it. Indeed, you always hear about specific methods and techniques. But you don't hear about how to think in order to apply them. In this note I'll try to sum up my experience of solving programming contest problems. However, some pieces of advice will also be applicable for olympiads in mathematics and your first steps in academic research.
So you've read a problem and you don't know how to solve it. Try the following techniques, some of them can often come handy.
##### Technique 1: "Total Recall"
Try to remember some similar problems that you had to solve. Quite many problems do not have a brand new idea. So probably, you can use your experience of solving a similar problem to solve this one.
##### Technique 2: "From Specific to General"
Let's say that you've found the solution for the problem (hurray!). Let's consider ...
will also be applicable for olympiads in mathematics and your first steps in
academicresearch
11.
Editorial of Global Round 11 #### General comments
Broadly speaking, problems A-B-C-D were "div2 problems", while F-G-H were "strong grandmaster problems" (with E staying in the middle). I did not expect anyone to solve all the problems and thus I decided to give the scoring F+G=H (so that maybe someone would have solved H).
<br><br>
Many of the problems (A, C, D, E, G) admit multiple solutions. Sometimes the core of the solution is the same (C, D) and sometimes the solutions are truly different (A, E, G).
<br><br>
If you are an experienced participant, I would like to hear your opinion on the problems. Feel free to comment on this post or send me a private message.
<br><br>
<spoiler summary="Overview of the problemset" >
The easiest problem of the contest, *A-Avoiding Zero*, is about rearranging an array of numbers. It is intended as a very easy problem that still requires to think.
Then, in *B-Chess Cheater* an intuitive (but nontrivial to prove) greedy approach is the way to go.
*C-The Hard Work of P...
least one research paper considering something similar). I decided that the
problem is beautiful, that some versions of this problem are known (and I actually found at least one
research paper
Tutorial of Codeforces Global Round 11
12.
Linear Basis (Xor Basis Extended) As part of the graduation requirements for my school, I have to complete a simple research project, so I decided to do something related to data structure and algorithms. I believe I have come out with a data structure that maintains the basis of vectors in $(\mathbb{Z}/m\mathbb{Z})^d$, where $m$ **may not be prime**. Since this was related to competitive programming, I think it is a good idea to share it here. Hopefully, this algorithm is actually novel :P
I would like to thank:
- [user:icypiggy,2021-12-26] for being my research mentor and tolerating my dumb questions
- [user:rama_pang,2021-12-26] and [user:adamant,2021-12-28] for their helpful suggestions and comments
Please comment under the blog or message me on codeforces if any parts are unclear or wrong. Also, I hope that some LGMs can help solve the open problems in this blog.
# Introduction
Maintaining the basis of vectors in $(\mathbb{Z}/2 \mathbb{Z})^d$, also known as the xor basis algorithm is a well-studie...
- [user:icypiggy,2021-12-26] for being my research mentor and tolerating my
dumb questions, As part of the graduation requirements for my school, I have to complete a
simpleresearch project
13.
Problem Topics Good Day to you!
I've been asked to make some topic-wise list of problems I've solved. Even though I couldn't involve all problems, I've tried to involve at least "few" problems at each topic I thought up (I'm sorry if I forgot about something "easy"). I've alredy made such list once anyway I've tried to include more problems now — so here it is:
<spoiler summary="aho">
http://www.spoj.com/problems/ADAJOBS/
URI 2226 (5) //[NICE][NUMBERS][DP]
http://www.spoj.com/problems/SUB_PROB/en/
http://codeforces.com/contest/696/problem/D 8
http://www.spoj.com/problems/AHOCUR/ 5 //Aho-Corassic + DP
https://www.codechef.com/problems/LYRC (5) //Sample aho-brute-force
http://codeforces.com/problemset/problem/346/B //Proposed by [user:bradyawn,2019-08-03]
</spoiler>
<spoiler summary="automat">
6861 [LA] //CYK
UVA 10679 //Suffix Automat
http://www.spoj.com/problems/STRMATCH/ //Suffix Automat — trie might do too
http://www.spoj.com/problems/NSUBST...
7673 — What a Simple Research (2) //[EASY][IMPLE]
14.
Codeforces: Results of 2018 Hi Codeforces!
February 2019 is already on the calendar, which means that I was late with the report for 2018. Better late than
never! Let's remember last year.
In 2018, [user:_kun_,2019-02-05], [user:300iq,2019-02-05] and [user:arsijo,2019-02-05] joined the team of coordinators. The work of the coordinators is headed
(and is the coordinator of the coordinators) [user:KAN,2019-02-05]. I really hope that a more measured schedule of preparing rounds by
a large team of coordinators will give a better insight into the contests. The main innovations in the platform are implemented
by me and the developers [user:kuviman,2019-02-05], [user:fcspartakm,2019-02-05], [user:MaximShipko,2019-02-05]. Great work on the organization of events and
prizes mailing was done by [user:gKseni,2019-02-05].
Special thanks to the writers of the problems and testers. It is your content that charges the community with life and unites
all of us. Thank you for the problems!
And now let's summarize...
audience * **Huawei** — research competition (marathon) with elements of
machine learning, wide international audience * **Huawei** — research competition (marathon)
with elements of
15.
On Multidimensional Range Queries The following question is frequently asked in Codeforces ([46390](https://codeforces.com/blog/entry/46390), [45157](https://codeforces.com/blog/entry/45157), [11324](https://codeforces.com/blog/entry/11324)): _Is there a 2D segment tree that supports range addition and range minimum?_ In this blog post I give evidence that such a data structure does not exist, or if it did exist it would not generalize to higher dimensions. In particular I show that if for all $d$ a $d$-dimensional data structure that performs such queries in $O(polylog(N))$ time did exist, then the [exponential time hypothesis](https://en.wikipedia.org/wiki/Exponential_time_hypothesis) would fail. Such a data structure exists for range addition and range sum, so this is a non-trivial claim separating the hardness of these problems.
## Update 2021:
A paper " Algorithms and Hardness for Multidimensional Range Updates and Queries" in ITCS 2021 by Joshua Lau and Angus Ritossa ([https://arxiv.org/abs/2101.02003](https:...
this exact data structure have not been given before, there has been a lot of
research on related, research on related topics. Some observations: 1. Klee's measure problem is
very related to Range
16.
Yandex.Algorithm 2017, third elimination round: editorial (with challenges, bells and whistles) This time I've decided to play with spoilers to faciliate the presentation as some of the guys here did before. Tell me what you think about this write-up!
#### Problem A. Shifts
Topics: dynamic programming.
Summary: the first "hard" problem of the contest. Knowing your basic DP problems helps a lot, but coming up with the precisely correct solution may take a lot of persistence.
Solution: Suppose that we are allowed to make left circular shifts as well as right ones.
<spoiler summary="Can you solve the problem in this case?">
First of all, making a shift is effectively moving a character to a different position in the string. Clearly, moving a character more than once makes no sense since we could have just moved it to its final destination instead without wasting any operations. Also, it obvious that the number of occurences of each character should be the same in both strings since it is preserved by shifts.
Now, consider the characters that are *not* moved by ...
Can you solve the problem much faster than $O(n^2
17.
Educational Codeforces Round 92 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1389] [contest:1389] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-07-28] Glazov, Adilbek [user:adedalic,2020-07-28] Dalabaev, Vladimir [user:vovuh,2020-07-28] Petrov, Ivan [us...
Organization for Nuclear Research (CERN) for a 5 Week Student Entrepreneurship
Programme, and are now, by the European Organization for Nuclear Research (CERN) for a 5 Week Student
Entrepreneurship
Announcement of Educational Codeforces Round 92 (Rated for Div. 2)
18.
Are we close to machines solving ICPC problems? Hi, all,
I with few other folks at [NEAR](http://near.ai/blog) work on teaching machines to program. A particularly exciting sub-project of that is teaching machines to solve competitive programming problems.
In this post I would like to give a quick overview of where the state of the art is today, what the major challenges are, why this is not a popular area of research, and how the CodeForces community can help to address some of the issues the program synthesis community is facing today.
We also have a certain budged allocated for this project, and we are paying to the CodeForces members who help us with some data annotation challenges. We have paid more than $10k in our first two annotation projects, and are launching three more projects today. Scroll to the end if you are interested.
Competitive programming as a benchmark
======================================
With the emergence of deep learning, neural networks started performing almost at a human level in many ta...
Microsoft Research to deliver it., challenging research task., major challenges are, why this is not a popular area of research, and how the
CodeForces community, today, what the major challenges are, why this is not a popular area of
research, and how the, 1. We will find a way to learn from few examples. One-shot learning is a hot
topic ofresearch, Microsoft Research has a long history of working on program synthesis. Here are
two good, The area of research that is tasked with automated program generation is called
Program Synthesis, The lack of data is also the primary reason why program synthesis is not a
popular area ofresearch, __Programming from description__ is a more recent area of research. Until the
emergence of Deep
19.
Codeforces Global Round 16 **Hello, Codeforces!**
On [contest_time:1566] we will host [contest:1566]. **<img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width: 200.0px;float: right;margin: 0 1.0em 1.0em 1.0em;max-width: 100.0%;max-height: 100.0%;">**
It is the fourth round of a 2021 series of [Codeforces Global Rounds](https://codeforces.com/blog/entry/65002). The rounds are open and rated for everybody.
The prizes for this round:
- 30 best participants get a t-shirt.
- 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.
The prizes for the 6-round series in 2021:
- In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT).
- The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
- The best 20 participants over all series get sweatshirts and place certificates.
Thanks to XTX, which in 2021 supported the gl...
Announcement of Codeforces Global Round 16
20.
Osijek Competitive Programming Camp 2023 winter — wrap Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a></center>
<center>
<b>Sponsored by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
<a href="https://www.think-cell.com/osijek2023"><img src="/predownloaded/97/88/97887beeb75a4601259414b36ecee0160c29d027.svg" height="40px" style="margin: 5px 5px 5px 5px;"></a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
</center>
The [Osijek competitive programming camp](https://ocpc.mathos.unios.hr) (also see the [announcement](https://codeforces.com/blog/entry/110945) on Codeforces) just concluded last Sunday, on February 26, and I'd lik...
follow, or using references to some advanced techniques, or sometimes even
research papers. There, hard to follow, or using references to some advanced techniques, or sometimes
evenresearch papers
21.
Codeforces Round #890 (Div. 2) #####Hi, Codeforces!
[user:Alexdat2000,2023-08-03], [user:Igorfardoc,2023-08-03], and I are pleased to invite you to our [contest:1856], which will be held on [contest_time:1856]. **This round will be rated for participants with a rating lower than 2100.**
We would like to thank:
- [user:errorgorn,2023-08-03] for coordinating the round.
- [user:Yuu,2023-08-03], [user:maomao90,2023-08-03], [user:thenymphsofdelphi,2023-08-03], [user:Dominater069,2023-08-03], [user:Mike4235,2023-08-03], [user:valeriu,2023-08-03], [user:irkstepanov,2023-08-03], [user:zengminghao,2023-08-03], [user:Gheal,2023-08-03], [user:DeMen100ns,2023-08-03], [user:FEDIKUS,2023-08-03], [user:thanhchauns2,2023-08-03], [user:MinaRagy06,2023-08-03], [user:Java,2023-08-03], [user:xudian,2023-08-03], [user:madlogic,2023-08-03], [user:squishybanana04,2023-08-03], [user:stefanbalaz2,2023-08-03], [user:kobebryan9,2023-08-03], [user:Murinh0,2023-08-03], [user:IlyinAD,2023-08-03], [user:Respectively,2023-08-03], [user:p...
as an excellent preparation for Ph.D. research in fields such as software
engineering, cybersecurity, programs also serve as an excellent preparation for Ph.D. research in fields
such as software
Announcement of Codeforces Round 890 (Div. 2) supported by Constructor Institute
22.
[Tutorial] Greedoids: a formal way to look at families of greedily-solvable problems _Disclaimer: This is not an introduction to greedy algorithms. Rather, it is only a way to formalize and internalize certain patterns that crop up while solving problems that can be solved using a greedy algorithm._
**Note for beginners:** If you're uncomfortable with proving the correctness of greedy algorithms, I would refer you to [this tutorial](https://web.stanford.edu/class/archive/cs/cs161/cs161.1138/handouts/120%20Guide%20to%20Greedy%20Algorithms.pdf) that describes two common ways of proving correctness — "greedy stays ahead" and "exchange arguments". For examples of such arguments, I would recommend trying to prove the correctness of standard greedy algorithms (such as choosing events to maximize number of non-overlapping events, Kruskal's algorithm, binary representation of an integer) using these methods, and using your favourite search engine to look up more examples.
Have you ever wondered why greedy algorithms sometimes magically seem to work? Or find them un...
important game (in fact, it has so many deep implications on combinatorics,
that it is an importantresearch, time and being more popular in the research community. Since this is a blog
only on greedy algorithms
23.
Ideone is evil and I can prove it (not anymore!) So, on the last round i wasnt at home, and therefore had to use another person's computer to do the contest. Waking up to close to the start time made me not be able to set up the IDE properly, so I thought "why not just use ideone"?
But what is Ideone anyway?
------------------
Well it *says* its an online compiler, so it must be a great alternative to a text editor to test things locally. However, little did I know that it was, in fact, a trap meticulously crafted by the devil, as I received those kind messages from codeforces:
There are 5 more of these.
Well, let me explain. This is what appears when you go into ideone:
Notice something wrong? Right at the corner of the screen...
this man, along with many others, is actually a bot (which can or cannot be
setup by SphereResearch, ://craft.co/ideone , it's Sphere Research Labs. Sphere... can you guess what it
relates to? Yes, [Sphere, According to https://craft.co/ideone , it's Sphere Research Labs. Sphere... can
you guess what it, Guys, good has won this battle. Sphere Research Labs [has
commented](https://codeforces.com/blog, That settles it. The Sphere Research Labs are in fact a company design to
destroy the lives of
24.
[Tutorial] Blossom Algorithm for General Matching in O(n^3) I have decided to write a tutorial on a topic not even [user:Um_nik,2021-06-29] knows! ([source](https://codeforces.com/blog/entry/92248))
In this tutorial, I will talk about the blossom algorithm, which solves the problem of **general matching**. In this problem, you are given an undirected graph and you need to select a subset of edges (called matched edges) so that no two edges share a vertex, and the number of matched edges is maximized. More common in competitive programming is bipartite matching, which is the same problem but when the graph is guaranteed to be bipartite. In competitive programming, general matching seems to get a lot of hate for being very challenging to implement. However, the blossom algorithm is quite beautiful, and important in the history of algorithm research.
It will help if you are already familiar with bipartite matching. I will discuss the high level ideas of the algorithm, but my main focus will be on the tricky implementation details. So you may...
beautiful, and important in the history of algorithm research., research. It will help if you are already familiar with bipartite matching. I
will discuss the high
25.
[Tutorial] Minimum cost (maximum) flow [Part 1: [Tutorial] My way of understanding Dinitz's ("Dinic's") algorithm](104960)
**Part 2: [Tutorial] Minimum cost (maximum) flow**
[Part 3: [Tutorial] More about minimum cost flows: potentials and Dinitz](105658)
#### Introduction
There is a section in our ICPC notebook from 2019 called "min cost dinic".
This blog started as an attempt to dissect what was written in there and
understand why it works. In time, I needed to refer to many general ideas about
flow, so it developed into a more general treatment of (min-cost) flow problems
and spawned an entire separate blog about maximum flow and Dinitz. Even after
splitting the blog, this blog was still too long, so I split it yet again.
This blog will deal with the basic ideas of minimum cost flow; there will be a
part 3, where I will generalize to a Dinitz-like algorithm and also talk a bit
about something called potentials.
This blog is somewhat more technical and formal than I would ideally write, but
there i...
lectures and research literature seem most concerned with just minimum cost
flow.
26.
I'm writing a book *UPD (2021-10-13): I've just discovered that I published this post for Russian audience only :(*
Hi everyone!
[I'm writing a book](https://en.algorithmica.org/hpc) about performance engineering: the art of optimizing algorithms beyond just asymptotic complexity.
The book walks through the main CPU optimization techniques such as caching, SIMD and pipelining while exploring many large case studies where we speed up some classic algorithm or a data structure, closely matching or even improving on the state-of-the-art.
You will probably not learn a single asymptotically faster algorithm there, but it will help you not to get TL when you are supposed to get AC, and sometimes get AC when you are supposed to get TL.
Among the stuff that you are probably most interested in:
- [A version of segment tree](https://github.com/sslotin/amh-code/blob/main/segtree/refactor2.cc) that can compute prefix sums in 2ns plus the time of the slowest memory read if the array doesn't fit in L...
the Floyd algorithm. I've only recently finished [the research
stage](https://github.com/sslotin, I've only recently finished [the research
stage](https://github.com/sslotin/amh-code) and I'm now
27.
Educational Codeforces Round 147 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1821] [contest:1821] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-04-19] Dalabaev, Ivan [user:BledDest,2023-04-19] Androsov, Maksim [user:Neon,2023-04-19] Mesche...
AI works. Plus, he'll also answer important questions about AI research and
its future implications._, works. Plus, he'll also answer important questions about AI research and its
future implications
Announcement of Educational Codeforces Round 147 (Rated for Div. 2)
28.
Codeforces: Results of 2020 [Annual Report] Hi Codeforces!
Yes, I know it's already April. Time flies so fast lately! Exactly a year ago we were just learning all the "delights" of lockdown.
So let's remember this 2020! What was it like? I don't know about you, but we had a hell of a lot of work.
I will now show you some graphs and you will be very surprised. Lockdown effect? Of course, but we did our best too.
Many thanks to everyone who did not stand aside! In 2020, we celebrated our 10th anniversary and crowdfunding money helps us grow and move forward. You helped us and each other. Thank you.
<a href="https://codeforces.com/10years/supporters">Thank you for your contribution!</a>
We've been working hard all year to make this community a better place. Did it work out? It's up to you to judge.
Many thanks to everyone who invested time and effort:
* [user:geranazavr555,2021-04-09], [user:kuviman,2021-04-09], [user:cannor147,2021-04-09] helped a lot with development and new features;
* [user:Una_Shem,2021-...
Rounds — Kotlin programming language contests * **Huawei** — research
competitions, ; research competitions (marathons) with elements of machine learning *
**Raiffeisenbank** &mdash
29.
SIT STAR Contest <b><i>Hello!</i></b>
<b><i>Together with colleagues [Schaffhausen Institute of Technology](https://sit.org/) we hold such an event. If you want to study in Switzerland, then perhaps this is your chance!</i></b>
<b><i>— Mike</i></b>
Hello, Codeforces!
<center>
<img alt="SIT" src="https://static.tildacdn.com/tild6536-6661-4864-b937-393639346635/sit_logo_black_short.svg" style="float:right; height: 200px; margin: 10px; max-width:50%;"/>
</center>
We are thrilled to announce a new SIT STAR Contest by the [Schaffhausen Institute of Technology in Switzerland](https://sit.org/). The winners will have a chance to get a fully-funded Master’s scholarship in Computer Science and Software Engineering.
**<font color="red">What is the SIT STAR Contest?</font>**
The goal of the SIT STAR Contest is to promote interest in the field of Computer Science and Software Engineering, give students an opportunity to demonstrate their knowledge of programming, and be considered for...
in today's hyper-connected, data-driven world. SIT bridges the gap between
education,research, and, -connected, data-driven world. SIT bridges the gap between education, research,
and applications for
30.
Editorial of CodeTON Round 4 (Div. 1 + Div. 2, Rated, Prizes!) [A. Beautiful Sequence](https://codeforces.com/contest/1810/problem/A)
<spoiler summary="Hint">
What is the necessary and sufficient condition?
</spoiler>
<spoiler summary="Tutorial">
The necessary and sufficient condition for a beautiful sequence is that there exist one $i$, such that $a_{i} \le i$. Just check the sequence for the condition.
</spoiler>
<spoiler summary="Solution">
~~~~~
#include<bits/stdc++.h>
using namespace std;
int a[100005];
void solve()
{
int n;
scanf("%d",&n);
for(int i =1;i <= n;i++) scanf("%d",&a[i]);
for(int i = 1;i <= n;i++) {
if(a[i] <= i) {
puts("YES");
return;
}
}
puts("NO");
}
int main()
{
int t;scanf("%d",&t);
while(t--) solve();
}
~~~~~
</spoiler>
[B. Candies](https://codeforces.com/contest/1810/problem/B)
<spoiler summary="Hint">
How the binary representation changes after an operation?
</spoiler>
<spoiler summary="Tutorial"...
Let's do the research when the second equation does not hold. Let $m_{1} =
\lbrace \frac{i(\phi - 1
31.
Codeforces Deltix Round Summer 2021 [Div.1 + Div.2] <a href="https://deltix.io/"><img alt="deltix" src="https://assets.codeforces.com/images/deltix/EcCsUtwbu1yq6Av.gif" style="float:right; height: 400px"/></a>
<p>Hi <span style="font-weight:bold">Code</span><span style="color:rgb(71,94,152);font-weight:bold">forces</span>!</p>
We are **[DELTIX](https://deltix.io/)**. Founded in 2005, DELTIX is one of the market leaders in software development for financial research and products for systematic and algorithmic trading. In 2020 DELTIX joined the EPAM family. Our mission is to turn promising ideas into breakthrough products fast.
We are experts in:
* aggregation, storage, and processing large volumes of time-series data
* data modeling
* testing and deployment of quantitative models
In our team we value such skills as:
* knowledge of algorithms
* high-performance coding
* low latency data streams processing
We are excited to announce that one of our products [TimeBase Community Edition](https://github.com/finos/...
development for financial research and products for systematic and algorithmic
trading. In 2020 DELTIX joined, software development for financial research and products for systematic and
algorithmic trading. In
32.
Educational Codeforces Round 33 [Rated for Div. 2] Hello Codeforces!
On [November 23, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=9&month=11&year=2017&hour=18&min=5&sec=0&p1=166) Educational Codeforces Round 33 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
As an experiment, the round will be **rated for Div. 2**. It will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were prepared by Mikhail [user:PikMike,2017-11-08] Piklyaev, Vladimir [user:0n25,2017-11-22] Petrov and me.
Good luck to all participants!
UPD: [Edito...
Announcement of Educational Codeforces Round 33 (Rated for Div. 2)
33.
And three streams this week Hi.
Even more streams are coming. For notifications, subscribe to my secondary channel for streams [Errichto 2](https://www.youtube.com/errichto2), or you can watch me on [Twitch](https://www.twitch.tv/errichto).
**Stream 1** — Monday [at 12:00 CEST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20190520T12&p1=262), I want to check out coding interview platforms like Leetcode. Here's [Youtube link](https://www.youtube.com/watch?v=1PhErzqrY6c).
**Stream 2** — Tuesday [at 9:00 CEST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20190521T09&p1=262). Algo research and writing old editorials. Links to [part 1](https://www.youtube.com/watch?v=XWf9DCMnpFM) and [part 2](https://www.youtube.com/watch?v=5rW-t3KFLM0) (the stream stopped for a few seconds and the new one started).
**Stream 3** — Friday [at 12:00 CEST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20190524T12&p1=262). Solving Codeforces problems, mainly around <s>div...
). Algo research and writing old editorials. Links to [part
1](https://www.youtube.com/watch?v, ?iso=20190521T09&p1=262). Algo research and writing old editorials. Links to
[part 1](https
34.
Educational Codeforces Round 130 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1697] [contest:1697] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-06-11] Dalabaev, Vladimir [user:vovuh,2022-06-11] Petrov, Ivan [user:BledDest,2022-06-11] Androsov, Mak...
dedicated to research and development of technical solutions, such as Secure
Networks, 5G and 6G, excellence dedicated to research and development of technical solutions, such
as Secure Networks, 5G
Announcement of Educational Codeforces Round 130 (Rated for Div. 2)
35.
Top 10 best Codeforces blog posts of 2021 (in my humble opinion) I really like good blog posts. And that's the main reason I like Codeforces. But as we all know, it's hard to find good blog posts here. So let's help each other and share our favorite posts, which were uploaded to Codeforces in the last year! I will share my top 10, and I encourage you to share some of your favorites in the comments.
#### 10. [Heuristic algorithm for Hamiltonian path in directed graphs](https://codeforces.com/blog/entry/90513) by [user:Miracle03,2021-12-24]
An absolutely incredible algorithm which kinda sometimes solves the Hamiltonian path problem on some random and special kind of graphs.
#### 9. [I compiled a list of almost all useful blogs ever published on Codeforces](https://codeforces.com/blog/entry/91363) by [user:parveen1981,2021-12-24]
This blog has a purpose that's similar to the purpose of the blog you're reading right now. A great source of interesting blog posts!
#### 8. [Fast modular multiplication](https://codeforces.com/blog/entry/96759...
36.
Montgomery Blair Informatics Tournament 2021 Spring Round (Registration live!) **Competitors can join our Discord server [here](https://discord.gg/CuWRkC8pG5)**.
The [Montgomery Blair HS Computer Team](https://www.mbhscompteam.org/) is proud to present the fourth iteration of the semi-annual **Montgomery Blair Informatics Tournament (mBIT)**, which will be held online from [10:00 AM — 2:00 PM EDT](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Montgomery+Blair+Informatics+Tournament+%28mBIT%29+2021+Spring+Round&iso=20210612T10&p1=263&ah=4) on **Saturday, June 12 (6/12/21)**. If you are interested in competing, please register at https://mbit.mbhs.edu/. The contest will be hosted on our personal servers at https://mbit.live/. All problems were written by the Montgomery Blair Computer Team, including [user:12tqian,2021-01-01], [user:gabrielwu,2021-04-01], [user:galen_colin,2021-05-14], [user:smax,2021-05-14], [user:meiron03,2021-05-14], [user:Blastman,2021-05-14], [user:alien_lover,2021-05-14], [user:czhang2718,2021-06-05], and [user:csytrn,2021...
amazing people at [United Therapeutics](https://www.unither.com/), [Wolfram
Research](https, /), [Wolfram Research](https://www.wolfram.com/), and
[AoPS](https://artofproblemsolving.com/)! We are
37.
OpenAI Codex can solve unseen Codeforces problems In this post, we will use the recent OpenAI Codex product based on GPT-3, first introduced in [Evaluating Large Language Models Trained on Code (Chen et al., 2021)](https://arxiv.org/abs/2107.03374) to solve some Codeforces problems.
We use the round [contest:1560] because the current version of the Codex model was released before this round. As the model has been trained on the Github data, it is possible that it memorized some solutions for older problems.
### Solving [problem:1560A] from the statement only
This is a simple problem, and the statement kind of explains what we should implement. Let's just give the plaintext statement to Codex:
<spoiler summary="Prompt">
Problem:
Polycarp doesn't like integers that are divisible by 3 or have the last digit 3
in their decimal representation.
Polycarp starts to write out the positive (greater than 0) integers which he likes:
1,2,4,5,7,8,10,11,14,16,….
Output the k-th element of this sequence (the elements are numbered...
[OpenAI's website](https://openai.com/) with an interesting research proposal.
Please do not use, will have a much more powerful Codeforces solver by say 2026, when the research
manages to combine, research manages to combine proof search methods with the GPT-3 architecture.
If I manage to read
38.
Analysis of polynomial hashing Unfortunately, most derivations of the chance of polynomial hashing collision are invalid, wrong, or misleading, and finding reliable public sources with proofs is incredibly difficult. This article is a formal analysis of the method. The goal of this article is to complement well-known empirical facts with theory, provide boundaries on the probability of collision, justify common choices, and advise against certain popular parameters.
There is no code in this article, and it's mostly theoretical. It's more of a summa of everything we know about polynomial hashing in integers rather than a guide for beginners. You'll probably find something of interest still. I do, however, describe some methods of cracking hashes, which I can provide code and additional explanation for if someone asks in the comments and some general guidelines in the last section of the present article.
## Table of contents
- The concept of polynomial hashing
- Classical justification of the coprimality r...
The following few sections will research universal collisions. A universal
collision is a string
39.
Codeforces Round #438 by 2nd Hello Barcelona Bootcamp with Sberbank <center>
<img src="/predownloaded/d1/0f/d10f26a5c5ba4fa2a31a0b69edc74c7799474e82.png">
</center>
Hi Codeforces!
The Codeforces Round #438 by Sberbank and Barcelona Bootcamp (Div. 1 + Div. 2 combined) is going to be held on [05 Oct at 9:05 (UTC+2)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=The+Codeforces+Round+%23438+by+Sberbank+and+Barcelona+Bootcamp&iso=20171005T0905&p1=31)! The round will be **rated for everyone**.
This round is organised in collaboration with [2nd Hello Barcelona ACM ICPC Bootcamp 2017](http://in.harbour.space/icpc/acm-icpc-hello-barcelona-bootcamp-autumn-2017/?utm_source=Codeforces) and supported by [Sberbank](http://www.sberbank.com/ru), the biggest commercial and investment bank of Central and Eastern Europe, with over 175 years of history.
150 students from 53 universities, including ITMO, University of New South Wales, St. Petersburg State University, MIPT, Ural Federal University, Tomsk State University, Novosibirsk State Univer...
University, Saratov State University, Samara National Research, Perm State
University, and many other, , Saratov State University, Samara National Research, Perm State University,
and many other top
40.
Codeforces Month of Blog Posts Results One and a half months ago [I proposed a challenge](https://codeforces.com/blog/entry/110840) to every one of you to get something from your drafts or from your head and actually write a blog post about it. I got a bunch of submissions, and you can find the links to all of them throughout this blog post (I was actually surprised that all entries were meaningful and interesting, so I definitely recommend checking them out). If you submitted an entry and I didn't mention it here, it is not purposeful! Indicate it via a direct message and I will include it here. It was just a bit hard to keep track of all submissions.
I went through all the submissions. Some of them were very complicated, and I tried my best to get the overall idea but I will need to come back to dive deeper into some technical proofs. However, I believe that these technicalities that I glanced through do not affect my decisions. We are ready to present the winners!
Regarding the first place, there was no doubt in my...
increasing subsequence queries. It's based on a research paper (with the
author of which I actually, queries. It's based on a research paper (with the author of which I actually
had an opportunity to
41.
Your true self **TL;DR stop making new accounts just to post blogs and post it on your main.**
Hello everyone!
I know it has been a while since I ever post a blog. I'm lazy ok? Today I want to tell you what went pretty bad recently: The existence of **alts**.
There are many type of alts which is being used for different stuffs, but let's put it in a side and talk about the most annoying type for me. Yeah, those unrated alts that appears everywhere, from recent blogs to comment sections.
If I am not wrong then every 1-2 days there would be an alt like that appear and post something like: Asking to be better at topics, talking about CP in india, or other stuffs. But what occur the most? Those who "catch" cheaters.
When **EVERY SINGLE CONTEST** that ends there would appear a blog that says "Cheater EXPOSED in Codeforces round #XYZ!" or "Google Kickstart round M code LEAKED!" from a random alt created shortly ago, drop a bunch of comments, and then some continue doing their "good" ...
" stuffs, some AFK forever. What do I mean? I did a research about users that
have "cheater" in, What do I mean? I did a research about users that have "cheater" in their
username (I know there
42.
Invitation to CodeChef January Cook-Off 2021 We invite you to participate in CodeChef’s [January Cook-Off](http://bit.ly/COOK126-Codeforces), this Sunday, 24th January, from [9:30 PM to 12:00 AM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=January+Cook-Off&iso=20210124T2130&p1=44&ah=2&am=30).
There will be **3 divisions**, each division containing **6 problems**!
This CookOff, [ByteDance](https://en.wikipedia.org/wiki/ByteDance) is joining CodeChef as the official contest recruiter! The tech giants, who have their presence globally established through a range of content platforms, are looking to hire for multiple positions for their Singapore office, including — Algorithm Engineers, Backend Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research Scientists, Frontend Engineers, Quality Assurance Engineer, Research Engineers, Software Engineer, and Site Reliability Engineers.
Joining us on the problem setting panel are:
- Setters: Ashish [user:Ashishgup,2021-01-22] Gupta, ...
Engineers, Research Scientists, Frontend Engineers, Quality Assurance Engineer,
Research Engineers, , Data Engineers, Data Scientist, Machine Learning Engineers, Research
Scientists, Frontend Engineers
43.
Educational Codeforces Round 143 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1795] [contest:1795] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-02-15] Dalabaev, Vladimir [user:vovuh,2023-02-15] Petrov, Ivan [user:BledDest,2023-02-15] Androsov, Ma...
processing media data;_ - _Conduct research in the field of Computer Vision:
classification, ;_ - _Conduct research in the field of Computer Vision: classification,
detection, segmentation
Announcement of Educational Codeforces Round 143 (Rated for Div. 2)
44.
Samara SAU ACM ICPC 2013-2014 Quarterfinal Qualification Contest: Editorial ### A. The Power of the Dark Side
(difficulty: easy)
Let's sort the parameters of every Jedi: $a \ge b \ge c$. The "coverted" Jedi obviously wants to use his strongest 2 parameters ($a_k,b_k$) against the opponent's weakest 2 ($b_i,c_i$) to get 2 victories as assuredly as possible; besides, the optimal order is $a_k$ against $b_i$ and $b_k$ against $c_i$, because if he can win when using them in the opposite order, then he'll win after swapping them, too. So we want to find all Jedis that have $a_k > b_i$ and $b_k > c_i$ for all $i$.
That's simple, because those are the same conditions as $a_k > B=\max(b_i)$ and $b_k > C=\max(c_i)$. When processing the input, we can count $B$, $C$ and then we just check for every Jedi if he satisfies these 2 conditions, in linear time.
I decided during the contest to code a solution which is a bit slower, but more powerful — it allows us to answer stronger versions of this problem like "which Jedis can we choose, if we're satisfied with...
### C. Victor's Research (diff: easy-medium)
45.
Register for the Montgomery Blair Informatics Tournament (mBIT) 2020 Fall Round! If you are interested in participating in the **Montgomery Blair Informatics Tournament (mBIT)**, which will be held online from [12:00-4:00 PM EST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Montgomery+Blair+Informatics+Tournament+%28mBIT%29+Fall+2020+Round&iso=20201114T12&p1=263&ah=4) on **Saturday, November 14 (11/14/20)**, please register at https://mbit.mbhs.edu/. The contest will be hosted on our personal servers at https://mbit.live/. All problems were written by the [Montgomery Blair HS Computer Team](https://codeforces.com/ratings/organization/2457), including [user:12tqian,2020-10-28], [user:gabrielwu,2020-10-28], [user:galen_colin,2020-10-28], [user:smax,2020-10-28], [user:meiron03,2020-10-28], [user:Blastman,2020-10-28], [user:czhang2718,2020-10-28], and [user:csytrn,2020-10-28]. Special thanks to [user:balbit,2020-11-12] for spending hours test solving our hardest problems!
mBIT is split into two divisions: **Standard** and **Advanced**. Teams may choose ...
/), [Wolfram Research](https://www.wolfram.com/), and [Art of Problem Solving
(AoPS)](https, ://www.unither.com/), [Wolfram Research](https://www.wolfram.com/), and [Art of
Problem Solving (AoPS
46.
Teams going to ACM ICPC World Finals 2018 I think it's good time for collecting teams that are going to WF this year. Let's complete the table together :)
Europe
======
| Count | Country | Region | University | Member 1 | Member 2 | Member 3 |
| ----- | ------- | ------ | ---------- | -------- | -------- | -------- |
| 1 | Belarus | NEERC | Belarusian State University | [user:progmatic,2018-04-12] | [user:Fedosik,2018-04-12] | [user:vilcheuski,2018-04-12] |
| 2 | Estonia | NEERC | University of Tartu | [user:oml1111,2018-04-12] | [user:hoomas,2018-04-12] | [user:k__mas,2018-04-12] |
| 3 | Kazakhstan | NEERC | Kazakh-British Technical University | [user:Zharaskhan,2018-04-12] | [user:AeonHQ,2018-04-12] | [user:NurlashKO,2018-04-12] |
| 4 | Russia | NEERC | Moscow Aviation Institute | [user:mingaleg,2018-04-12] | [user:SirRembocodina,2018-04-12] | [user:i.trofimow,2018-04-12] |
| 5 | Russia | NEERC | Moscow Institute of Physics & Technology | [user:Golovanov399,2018-04-12] | [user:Kostroma,2018-04-12] | [user:I_hate_A...
--o_o--V,2018-04-12] | [user:gritukan,2018-04-12] | | 7 | Russia | NEERC |
NationalResearch, -12] | [user:gritukan,2018-04-12] | | 7 | Russia | NEERC | National Research
University Higher
47.
How to read my blogs Hi everyone!
I saw that a lot of people write meta blogs recently. As my blog count approaches 90, I feel like it may make a lot of sense to write another one that kind of focuses on the philosophy behind my blogs and explains potential readers what they should expect from my blogs and how to approach them. So, without further ado...
##### Tldr.
1. Read my blogs if and only if the general setup itself appeals to you. Don't feel obliged to do it to get better at competitive programming.
2. Don't be driven away by seemingly dense math notation if the topic looks interesting. Ask questions if something is difficult to comprehend, I will explain in a more detail and it will help others too.
3. Be ready to fill some possible gaps in the story yourself, as an exercise.
4. Be open-minded about analyzing setup in general, rather than working towards predetermined goal.
5. Be prepared to see too little explanation on how abstract nonsense from my blogs connects with concrete applic...
essentially two ways of explaining things: 1. From result to research. This is
western approach, when, 1. From result to research. This is western approach, when we start by clearly
defining the end
48.
ICPC WF 2021 Prediction Game Good luck and have fun to all finalists!
I suggest to us(the fans) to play the following game:
**Rules of the game:**
Choose your top 12 teams, this will be your prediction for the ICPC final. For each team you choose, you can get points. The conditions are as follows:
- if the team gets a medal, then you earn +2 points
- if the team gets the medal you predicted, then you earn +1 point. In your prediction, we will assume that the first 4 teams get gold medals, the next 4 teams get silver medals and the last 4 teams — bronze medals.
- if the team gets the predicted place, then you earn +2 point.
Thus, one team can bring up to 5 points.
The points of your prediction are the sum of the points of the 12 teams you have chosen.
If you want to participate in the game, you can submit your prediction [here](https://codeforces.com/contestInvitation/771115929227f4dcf45bca9788327f7ab6462d3f).
Also, you can check your prediction [here](https://codeforces.com/conte...
1. National Research University Higher School of Economics, summary="His prediction"> 1. National Research University Higher School of
Economics — +2
49.
2023 KSAAC Summer · solved.ac Arena #4 Announcement Hi, I am [user:TheQueenOfHatred,2023-08-15], staff of [solved.ac](https://solved.ac/en).
We will hold 2023 KSA Automata Summer Contest · Arena #4. The problems are prepared by Automata, algorithmic problem solving research group of [Korea Science Academy of KAIST](https://www.ksa.hs.kr/Eng).
- Time: https://www.timeanddate.com/worldclock/fixedtime.html?iso=20230818T1930&p1=235&ah=4&am=30 270 minutes
- No. of Problems: 10, 100 points each = 1000 points total
- The questions are sorted in order of difficulty expected by the jury.
- **Statements are available in both English and Korean.**
- Every problem has **partial points**.
- The scoreboard will freeze 60 minutes before the contest ends.
- There are bonus time/memory limits for some languages. Check [here](https://help.acmicpc.net/language/info) for details.
- Editorial will be posted after the contest ends.
Please refer to the following guide for registering in the Arena contest:
- https://help.solved.ac/en/arena/g...
, algorithmic problem solving research group of [Korea Science Academy of
KAIST](https://www.ksa.hs.kr
50.
Setup for remote team competitions Hi. Remote team competitions/trainings became something we have to deal with nowadays and I think having a setup you feel comfortable with is something really valuable and nontrivial to achieve that you definitely should not neglect, effort put into this will quickly pay off. In our Polish Mafia team we already participated in many remote competitions
and struggled with various technical problems and through trial and error we converged to
a setup which I believe is close to ideal. Many of these pieces of advice are applicable to all kinds of remote collaboration, e.g. working on some university projects or research problems, however I felt the biggest need for it during these competitions since they are periods when I really need to be focused hard.
1) Communication <br>
The most important part in remote collaboration is communication. I definitely recommend PUSH TO TALK
(that is — an option where you talk if and only if you hold a specified key).
Background noises of o...
university projects or research problems, however I felt the biggest need for
it during these
51.
Educational Codeforces Round 61 [Rated for Div. 2] 
Hello Codeforces!
On [contest_time:1132] [contest:1132] will start.
This round is organised in collaboration with Hello Muscat Programming Bootcamp and supported by Sberbank, General Partner of the boot camp and one of the largest banking leaders of Eastern Europe, providing thousands of jobs and innovation in the financial industry.
As the Hello Muscat Programming Bootcamp’s General Partner, Sberbank made it possible for students from some of the world’s top universities to attend the bootcamp, by sponsoring their participation. This includes students from Saint-Petersburg State University, Moscow Institute of Physics and Technology (MIPT), Penza State University, National Research Mordovia State University; MRSU, ITMO, Higher School of Economics / Moscow, Volgograd State Technical University, Lobachevsky State University of Nizhni Novgorod, Moscow Aviation Institute, Tyumen industrial University, University of Haifa, Northern (Arctic...
Technology (MIPT), Penza State University, National Research Mordovia State
University; MRSU, ITMO, ), Penza State University, National Research Mordovia State University; MRSU,
ITMO, Higher School of
Announcement of Educational Codeforces Round 61 (Rated for Div. 2)
52.
Elo-MMR ratings go live on CodeChef! Readers of my Codeforces blog may recall that [user:inutard,2022-07-10] and I have been experimenting with rating systems for quite some time. Last year, we demonstrated how to [break the Topcoder system](https://codeforces.com/blog/entry/87848), and [published our findings](https://github.com/EbTech/Elo-MMR/blob/master/paper/EloMMR.pdf) at the World Wide Web 2021 research conference. There, we derived a new Bayesian rating system from first principles. This system was specifically motivated by sport programming, though it may in theory be applied to any sport that ranks lots of contestants. Recently, it was adopted by the [Canadian contest judge, DMOJ](https://dmoj.ca/post/206-ratings-migrated-to-elo-mmr).
Now, in collaboration with the CodeChef admins, we are pleased to announce that upon the completion of [July Lunchtime](https://www.codechef.com/LTIME110), the Elo-MMR rating system goes live on [CodeChef.com](https://codechef.com)! While recognizing that any rating system migrat...
naturally from the mathematical derivation. For details, please see the latest
revision of [ourresearch, /EbTech/Elo-MMR/blob/master/paper/EloMMR.pdf) at the World Wide Web 2021
research conference. There, we, ://www.microsoft.com/en-us/research/project/trueskill-ranking-system/), the
publicly displayed rating will be a
53.
Osijek Competitive Programming Camp 2023 fall — wrap Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a></center>
<center>
<b>Supported by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="50px" style="margin: 5px 5px 5px 5px;"></a>
<a href="https://icpc.foundation/"><img src="https://ocpc.mathos.unios.hr/images/ICPC.svg" height="70px" style="margin: 5px 5px 5px 5px;"></a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="50px" style="margin: 5px 5px 5px 5px;"></a><br>
<a href="https://artofproblemsolving.com/"><img src="https://ocpc.mathos.unios.hr/images/aops.svg" height="40px" style="margin: 5px 5px 5px 5px;"></a>
<a href="https://www.wolfram.com/">
<img src="https://ocpc.mathos.unios.hr/images/wolfram.png" height="40...
**Wolfram Research**, who offered all camp participants free 6 months of
Wolfram|One Personal Edition, camp, we grew in supporters a bit, as this time we were also supported by
**WolframResearch**, who
54.
Codeforces Round #488 by NEAR **UPD** note that the score distribution has changed
**UPD2:** [user:LHiC,2018-06-17] found a bug in the author solution of div1-F. We are working on the situation.
**UPD3:** we found a correct solution for div1-F and both submissions made during the contest pass all the tests against the correct solution. The round remains rated.
Hi, everybody,
Codeforces round 488 for both divisions will take place on [contest_time:993]. The round will be 2.5 hours long (which is 30 minutes longer than usual).
The contest is created by [NEAR](http://near.ai/blog) and its friends. NEAR is working on teaching machines to compete in programming competitions. Read [our blog post](http://codeforces.com/blog/entry/59746) to learn more about the state of the art in the program synthesis today, our vision, and how you can help us bring this vision to reality.
The contest will feature 6 problems for each division, with 4 problems shared across them.
The problems for the contest are from t...
data for research. Read more [here](http://codeforces.com/blog/entry/59802)., for people to help us label competitive programming data for research. Read
more [here](http
Announcement of Codeforces Round 488 by NEAR (Div. 1)
Announcement of Codeforces Round 488 by NEAR (Div. 2)
55.
2024 KSA Automata Winter Contest · Arena #22 Announcement Hi, I am [user:Konijntje,2024-02-22], staff of solved.ac.
We will hold 2024 KSA Automata Winter Contest · Arena #22. The problems are prepared by Automata, an algorithmic problem-solving research group of [Korea Science Academy of KAIST](https://www.ksa.hs.kr/Eng). ([solved.ac arena page](http://solved.ac/arena/) / [acmicpc.net contest page](https://www.acmicpc.net/contest/view/1238)).
(huge thanks to [user:wizardrabbit,2024-02-22] for making this banner)
### Contest Information
- Time: [https://www.timeanddate.com/worldclock/fixedtime.html?msg=2024+KSA+Automata+Winter+Contest&iso=20240224T1900&p1=235&ah=5](https://www.timeanddate.com/worldclock/fixedtime.html?msg=2024+KSA+Automata+Winter+Contest&iso=20240224T1900&p1=235&ah=5), 300 minutes
- No. of Problems: 11, 100 points each = 1100 points total
- The questions are sorted in order of difficulty expected...
Contest · Arena #22. The problems are prepared by Automata, an algorithmic
problem-solvingresearch, , an algorithmic problem-solving research group of [Korea Science Academy of
KAIST](https
56.
[Variants] An interesting counting problem related to square product ## The statement:
Given three integers $n, k, p$, $(1 \leq k \leq n < p)$.
Count the number of array $a[]$ of size $k$ that satisfied
- $1 \leq a_1 < a_2 < \dots < a_k \leq n$
- $a_i \times a_j$ is perfect square $\forall 1 \leq i < j \leq k$
Since the result can be big, output it under modulo $p$.
For convenient, you can assume $p$ is a large constant prime $10^9 + 7$
**Notice that in this blog, we will solve for generalized harder variants**
**For original problem you can see in this blog [[Tutorial] An interesting counting problem related to square product](https://codeforces.cc/blog/entry/96379)**
---
## Extra Tasks
**These are harder variants, and generalization from the original problem. You can see more detail [here](https://codeforces.cc/blog/entry/96379)**
*Marked as solved only if tested with atleast $10^6$ queries
**[Solved A](https://codeforces.cc/blog/entry/964...
But while doing research for task **H**, I found an improvement
57.
Community Solutions to Abuse of Rules Hi!
Codeforces is filled with great people, but it is also has plenty of users that abuse the system, and dampen other people's fun though their actions. A few problems I put under the spotlight
Problems:
------------------
<span style="color:red"><b>A</span> unrateds, alts, and rating-manipulating contestants that win contests below their division, stealing the victory and some rating from legitimate participants. See the last 4-5 div 2's for sufficient examples of experts and specialists losing wins to these fakes. This can be extended to cheaters in general, but there is already a system for that in place.
<span style="color:blue"><b>B</b></span> Users who make alts to shield themselves from backlash when commenting, potentially to make hurtful statements. Many of us have seen the abuse that they spew.
I've labeleld things as <span style="color:red"><b>A</span> and <span style="color:blue"><b>B</b></span> to refer to the problem I am talking about.
I've done my rese...
I've done my research:, research: Past Suggestions: ------------------ A Make div 2
58.
April Fools Day Contest 2022 Editorial All problems were created and prepared by me and [user:magnus.hegdahl,2022-04-01]. Thanks to [user:BucketPotato,2022-04-01], [user:Monogon,2022-04-01], and [user:Priyam2k,2022-04-01] for valuable feedback and testing. Special thanks to [user:MikeMirzayanov,2022-04-01] for coming up with the idea and preparing the unique checker for [problem:1663H]. I hope you enjoyed the contest, and found it to be an interesting series of puzzles.
Example solution code written by [user:Agnimandur,2022-04-01] is provided for each problem.
### [problem:1663A]
<spoiler summary="Clue 1">
The problem statement is the title of the problem.
</spoiler>
<spoiler summary="Clue 2">
Re-read the original announcement blog.
</spoiler>
<spoiler summary="Solution">
If you carefully read [the announcement blog](https://codeforces.com/blog/entry/101364), you will notice that I especially thanked [user:BucketPotato,2022-04-01] for testing. Just print "BucketPotato".
</spoiler>
<spoiler summary=...
Google research into how Pascal and C++ work will eventually lead you, : ``[ ] ( ) ! +``. Brief research will demonstrate a mapping from each english
letter to a JSFuck string, Brief research will demonstrate a mapping from each english letter to a JSFuck
string. Two letters
Tutorial of April Fools Day Contest 2022
59.
The Psychology of Competition Participating in a big competition like IOI or ICPC can be intimidating, the worst thing that might happen to you is that you manage to get nervous enough to enter that adrenaline-fueled fight or flight state, you start feeling that you need to get out of the contest fast. An easy bruteforce solution that would take you 2 minutes to code in a normal environment suddenly requires 10 minutes, or at least that's what happened to me the last 3 major competitions I participated in (APIO 2014, IOI 2014 and APIO 2015), while it wasn't very noticeable in APIO 2014 -I quickly forgot about it because it was my first medal a bronze one- and I blamed that state on sickness in IOI 2014, after APIO 2015 it became clear to me that I'm making the mistakes over and over.
If you're really new to competitive programming, someone who doesn't really care much about the result, or someone who's trained since the age of 6 you probably won't relate to these issues, but after I've done some research I reali...
after I've done some research I realized that this is more common than I
expected. The same pattern, since the age of 6 you probably won't relate to these issues, but after I've
done someresearch I
60.
CC February Long 2021 We invite you to participate in [CodeChef’s February Long Challenge](http://bit.ly/Codeforces-FEB21), this Friday, 5th February, from [15:00 IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=February+Long+Challenge&iso=20210205T15&p1=44) onwards.
The contest will be open for 10 days i.e. until 15th February.
The February Long Challenge is going to have ByteDance and Codenation as the official contest recruiters! Yep, TikTok's parent company is going to be looking to hire for multiple positions for their Singapore office, including — Algorithm Engineers, Backend Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research Scientists, Frontend Engineers, Quality Assurance Engineer, Research Engineers, Software Engineer, and Site Reliability Engineers. Codenation Innovation Labs is hiring programmers for the Software Development Engineer role and its Junior Trilogy University (Intern Programme).
Also, if you have some original and engaging p...
Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research
Scientists, Frontend, Scientist, Machine Learning Engineers, Research Scientists, Frontend
Engineers, Quality Assurance
61.
A Public Apology (+Compensation) The Introduction
----------------
On March 32nd of this year I created a blog post to share some new coding techniques that are quite easy to code and serve as very powerful optimizations (Context: [https://codeforces.com/blog/entry/58667](https://codeforces.com/blog/entry/58667)).
Now of course I know I single-handedly transformed the competitive programming meta as problems had to be done according to new standards now that it is possible to make O(N) code work O(1). Super fast. However, I have to share an upsetting discovery that I made. This blog post might be too sad for you, so discretion is advised. I have added certain checkpoints within this post where you can take a break if you get too sad and you may resume reading later. I have also added some cute pictures of animals to help out with your sadness.
The Story
---------
It all started yesterday, when I used my usual O(1) trick to O(N) trick on problem E2 from the last contest (It seems that Mirzayanov has not a...
62.
Marek Cygan was awarded an ERC (European Research Council) Starting Grant Marek [user:marek.cygan,2016-11-05] Cygan from the University of Warsaw [will allocate the ERC grant](http://en.uw.edu.pl/young-scientist-and-algorithms/) – 1,4 million euro to work on algorithms. “Technology transfer between modern algorithmic paradigms” is the name of his research project which will be carried out at the University of Warsaw.
Before Marek Cygan became an academic teacher he was taking part in IT competitions. In 2005 he won [Google Code Jam](https://community.topcoder.com/pl/?module=Static&d1=google05&d2=overview). Two years later together with Marcin Pilipczuk and Filip Wolski won the [ACM-ICPC in Tokio.](https://icpc.baylor.edu/community/history-icpc-2007). As a Phd student of Institute of Informatics of the University of Warsaw Marek Cygan got a 3rd place in [TopCoder Open in Las Vegas](http://www.topcoder.com/tc?module=Static&d1=tournaments&d2=tco09&d3=overview&d4=overview).
He received many scholarships from the state institutions, among others, from the ...
Marek Cygan was awarded an ERC (European Research Council) Starting Grant, . “Technology transfer between modern algorithmic paradigms” is the name of his
research project which
63.
Support of JavaScript V8 and Some Benchmarks I've found some time to support JavaScript, which is so popular now. I chose V8 as the most developed implementation of JavaScript.
With the help of a tambourine and a liter of cola [I successfully compiled it on Windows](http://assets.codeforces.com/files/v8-3.32.0.7z). Funny, I was ready to implement workaround to support reading from stdin in JavaScript, but `d8` already supports it! Just use `readline()` to read line from the input.
Here is an example of A+B:
~~~~~
var line = readline().split(' ')
print(parseInt(line[0]) + parseInt(line[1]))
~~~~~
Interesting fact, that if there is no line-break (\r\n) at the end of line, then `readline()` returns `undefined`. So it is one more reason for good rule: each line should end with eoln.
As a tiny research I've implemented HeapSort on C++, Java and JavaScript. I have an opinion that all dynamic typed languages are very slow. But...
I've implemented HeapSort on $10^7$ elements from 0 to 9999999. I think it is good benc...
one more reason for good rule: each line should end with eoln. As a tiny
research I've implemented, As a tiny research I've implemented HeapSort on C++, Java and JavaScript. I
have an opinion that
64.
2023 Girls Programming League Hello Codeforces!
The Harker Upper School's Programming Club would love to invite middle school and high schoolers to our Girls Programming League (GPL) 2023 **virtual competitive programming contest on Saturday, September 16 from 8:45 AM to 2:30 PM PST**.
The Girls Programming League is a one-day event comprising a programming contest, panel discussion, and awards, with the goal to inspire and empower women to participate in computer science, technology, and AI. Our theme this year is “Computer Science and Artificial Intelligence,” which we believe is a rapidly growing field that has important impacts and fascinating applications to explore.
There will be **two divisions: novice and advanced**. The contest is open to all middle and high school students identifying as female or non-binary. Students can form **teams of up to 3**. We will also be awarding monetary prizes, in the form of Amazon gift cards, to the top 3 teams of each division.
We'll also be featuring a panel...
China Go-To-Market in Arm's IOT Line of Business, - Dr. Kim Hazelwood, Senior
Director of AIResearch, - Dr. Kim Hazelwood, Senior Director of AI Research and Engineering at Meta,
65.
"The bug" — old brutal russian game for programmers On the Internet since 2004 there is a game ["Bug"](http://buglab.ru). This is in russian, but you can use the google translator for translate all page, or ask me if there is something that is not clear after translation.
**Goal of game** — build a correct labyrinth 19 x 29 for bug. Result — number of bug's movements from start point to finish point. The results on the site are sorted by the amount of movement of the bug for the passage of the labyrinth. Algorithm of bug's movement:
>>Bug always starts movement from the upper left corner, and the exit is always in the lower right corner. The bug is not moving optimally, but in the following way: he goes to where he was not yet, or was there less often. Passing every cell of the labyrinth, the beetle remembers: how many times he was in this cell and when thinking about the direction of his movement at some particular moment he looks: how many times he was in the cell from down side, how many from the right side, how man...
and research this algorithm. Perhaps, it will be possible to shift the leaders
from their pedestal, Those interested are invited to play the game "Bug", to generate labyrinths and
research this
66.
Count a, b, c satisfy a + b + c <= S and a * b * c <= T for large S, T ### Statement
This question is based on bonus of [this problem](https://atcoder.jp/contests/abc214/tasks/abc214_b).
We need to count such non-negative integer triple $(a, b, c)$ that satisfy $(0 \leq a + b + c \leq S)$ and $(0 \leq a \times b \times c \leq T)$.
Since the result may be very big, you can either use **bignum** or **modulo** $10^9 + 7$ for convention
----------
**Notice that:**
- $(0, 0, 1) \neq (0, 1, 0) \neq (1, 0, 0)$
----------
**Constraint:**
- $0 \leq S, T \leq 10^{18}$
- $0 \leq a, b, c$
----------
**No Time Limit. But expect to be 10 seconds**
----------
**Memory Limit: 1Gb**
----------
**Input:**
- A single line contain only two positive **60-bit integers** $S$ and $T$ ($0 \leq S, T \leq 10^{18}$)
----------
**Output:**
- Print a single integer, the number of positive tuple satisfy mathematical condition
-----------------------------------
**Example:**
<spoiler summary="Example 0">
```css
...
### Current Research, Research When $S \leq \lfloor \frac
67.
Новости Факультета Компьютерных Наук ВШЭ В этом году первый набор [Факультета Компьютерных Наук](http://bit.ly/25msmZi) заканчивает третий курс, у них прошел первый год специализаций (предыдущие посты про новости ФКН: [1](http://codeforces.com/blog/entry/45054), [2](http://codeforces.com/blog/entry/18801), [3](http://codeforces.com/blog/entry/17195), [4](http://codeforces.com/blog/entry/12859), [5](http://codeforces.com/blog/entry/11918)).
Все студенты 3-го года обучения прошли курс по машинному обучению от [Евгения Соколова](https://www.hse.ru/staff/esokolov) (автора известной [специализации на Coursera](https://goo.gl/1nf8KS) и руководителя отдела машинного обучения сервиса [Яндекс.Дзен](https://goo.gl/Pnzp7S)). Если вы еще учитесь в школе, то вы можете послушать Евгения в [летней школе ФКН](https://goo.gl/0Ztkqf); также он отвечает за преподавание машинного обучения в [августовской параллели A-ML ЛКШ](http://lksh.ru/sis/2017/parallel-a.shtml).
Также общим был курс методов оптимизации, состоявший из непрерывной части ...
году были представители Яндекса, Google Research, Samsung, Parallels, Opera,
Банка Открытие и др., /research/people/yekhanin/) (Microsoft Research), [Нови
Квадрианто](http://users.sussex.ac.uk/~nq28, ://www.microsoft.com/en-us/research/people/yekhanin/) (Microsoft Research),
[Нови Квадрианто](http
68.
A simple introduction to "Segment tree beats" **This blog is just a back up of [http://codeforces.com/blog/entry/57319](http://codeforces.com/blog/entry/57319) to prevent this tutorial from discarding after [user:jiry_2,2018-10-17] is banned.**
Hi, I’d like to introduce a simple trick about segment tree in this blog as I promised in [this comment](http://codeforces.com/blog/entry/54750?#comment-387957). Sorry for the long delay, as a sophomore in Peking University, I've just finished a tired semester and a painful final exam. And now I finally have enough time to do a simple introduction to this interesting algorithm.
It may be a huge project for me since my English is not good. I think I will finish this blog in several steps and I will try to finish it as soon as possible :)
In China, all of the 15 candidates for the Chinese National Team are asked to write a simple research report about algorithms in informatics Olympiad, and the score will be counted in the final selection. There are many interesting ideas and algorit...
research report about algorithms in informatics Olympiad, and the score will be
counted in the final
69.
2022 Harker Programming Invitational Hello Codeforces!
The Harker Programming Club would love to invite middle school and high schoolers to our Harker Programming Invitational (HPI) 2022 event on [Sunday, March 13 from 8:00 AM to 2:45 PM PST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=HPI+2022&iso=20220313T08&p1=224&ah=8). This year the theme of our contest will be “CS & Space.”
The Harker Programming Invitational is a one-day event consisting of a programming contest, keynote speech, panel discussion, and awards, with the goal to inspire and empower students to participate in computer science, technology, and AI. The competition will provide aspiring students with the opportunity to solve creative programming problems, while the keynote speech and panel discussion aim to give the participants insight into the fields within Computer Science and Space.
Teams of up to 3 students will participate in the regular and tiebreaker rounds, which are 1.5 and 1 hour long, respectively. There will be two divis...
Dr. John Bresina, who is a Senior Research Computer Scientist at NASA Ames
Research Center, with, Our keynote speaker will be Dr. John Bresina, who is a Senior Research Computer
Scientist at NASA
70.
Tutorial on Zeta Transform, Mobius Transform and Subset Sum Convolution **Pre-requisite**: Go through the Zeta/SOS DP/Yate's DP blog [here](https://codeforces.com/blog/entry/45223)
**Source**: This blog post is an aggregation of the explanation done by [user:arjunarul,2019-12-26] in this [video](https://youtu.be/UOTCTbm1NrQ?list=PLi0ZM-RCX5nsTc2Z6woHr5qoF6n3b-thO), a comment by [user:rajat1603,2019-12-26] [here](https://codeforces.com/blog/entry/57250?#comment-409117) and the paper on [Fast Subset Convolution](http://people.csail.mit.edu/rrw/presentations/subset-conv.pdf)
**Notation**:
1. set $s$ and mask $s$ are used interchangeably meaning the same thing.
2. $a \setminus b$ would mean set subtraction, i.e subtracting set $b$ from set $a$.
3. $|s|$ refers to the cardinality, i.e the size of the set $s$.
4. $\sum_{s' \subseteq s} f(s')$ refers to summing function $f$ over all possible subsets (aka submasks) $s'$ of $s$.
**Aim**: Given functions $f$ and $g$ both from $[0, 2^n)$ to integers. Can be represented as arrays $f[]$ and $g[]$ r...
you can then you had the potential to publish the research paper mentioned in
the source.
71.
Invitation to CodeChef January Lunchtime 2021 [Replay of Codeflows] We invite you to participate in CodeChef’s [January Lunchtime](https://bit.ly/LTIME92-Codeforces) on 30th January from [9:00 PM to 12:00 AM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=January+Lunchtime&iso=20210130T21&p1=44&ah=3). **Note the unusual time**.
There will be **3 divisions**, each division containing **6 problems**!
This Lunchtime, [ByteDance](https://en.wikipedia.org/wiki/ByteDance) is joining CodeChef as the official contest recruiter! The tech giants, who have their presence globally established through a range of content platforms, are looking to hire for multiple positions for their Singapore office, including — Algorithm Engineers, Backend Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research Scientists, Frontend Engineers, Quality Assurance Engineer, Research Engineers, Software Engineer, and Site Reliability Engineers.
Joining us on the problem setting panel are:
- Admins: Ashish [user:ashishgup,2020-12-...
Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research
Scientists, Frontend, Learning Engineers, Research Scientists, Frontend Engineers, Quality Assurance
Engineer,Research
72.
Teaching algorithms to high school students in Ethiopia? Hi Codeforces!
Last year, I went to an event called AddisCoder as a teaching assistant and it is being offered again this year! AddisCoder is a 4-week summer program to introduce high schoolers in Ethiopia to programming and algorithms. It was one of the most memorable events in my life because I got to know about another country, met brilliant students and teaching assistants that were super friendly and cool (and I also had lots of fun exploring Ethiopia with them). We TAs worked together to make problemsets for the students and helped them through the problems.
The students are very good. There will be about 170 students this year. Alumni have gone on to study at Harvard, MIT, Princeton, Columbia, Brown, and many other institutions in the U.S., Ethiopia, Germany, and U.A.E. They have also gone on to work both as interns and full-time software engineers at Facebook, Google, Microsoft, Oracle, etc. A few alumni from the first offering of the course are now pursuing their PhDs ...
[computer science professor](http://people.seas.harvard.edu/~minilek/) with a
research focus on, /~minilek/) with a research focus on algorithms who was influenced by platforms
like Codeforces and
73.
ACM ICPC 2016−2017, Northeastern European Regional Contest [Результаты](http://neerc.ifmo.ru/information/standings.html)
[Запись видеотрансляции разбора задач и церемонии закрытия](https://www.youtube.com/watch?v=fN25KkNYsjA)
[Запись видеотрансляции соревнования](https://www.youtube.com/watch?v=k14LmtAWqDs)
Список команд финалистов: <br/>
**SPb State University 1 (Ershov, Pyshkin, Sayranov)** <br/>
**SPb ITMO University 1 (Belonogov, Smykalov, Zban)** <br/>
**Moscow Institute of Physics and Technology 1 (Semenov, Smirnov, Zhuk)** <br/>
**Ural Federal University 1 (Borozdin, Kungurtsev, Leskov)** <br/>
**Perm State University 1 (Kuchumov, Mayorov, Pryshchenko)** <br/>
**Belarusian SU of Information and Radioelectron. 1 (Sobal, Valchok, Vistiazh)** <br/>
**Vilnius University (Jadenkus, Klimavičius, Traškevičius)** <br/>
**Novosibirsk State University 1 (Smirnov, Viktorov, Vishnevskiy)** <br/>
**SPb Academic University 2 (Stepanov, Zhidkov, Zuev)** <br/>
**Latvia University 1 (Kuznecovs, Pakalns, Zajakins)** <br/>
**Saratov St...
, Mamikonyan, Sahakyan)**
**Samara National Research University 1 (Bezrukov, Muravjev, Ponomarev, /> **Yerevan State University 1 (Harutyunyan, Mamikonyan, Sahakyan)**
**Samara National Research
74.
Problem Proposal with Editorial | Div2 B/C So I had proposed a problem few months back but didn't get the time to prepare an entire contest. Wanted to share the problem and it's editorial which I wrote while proposing.
Came across something similar while reading and implementing a research paper.
<spoiler summary="Problem statement">
There are **n** data items (d1, d2, .. , dn) and an integer **m** less than equal to **n**.<br>
Next you are given a NxN matrix **SIM** such that **SIM[i][j]** = similarity between di and dj.
For every data item di, Choose any **m**-sized subset **s** of the **n** items and evaluate sum of similarities between di and dj such that dj belongs to the chosen subset **s**, call this value the score for di given subset s or **d(i,s)**.
Define Si = score of data item i = max d(i,S) over all possible m sized subsets S
find x where x = max Si over all i (from 1 to n)<br>
if there is more than 1 valid answer then minimize x.
</spoiler>
<spoiler summary="Constraints">
SIM[i][j] = SIM[...
something similar while reading and implementing a research paper. , Came across something similar while reading and implementing a research paper.
75.
How to Interpret Contest Ratings **UPDATE: the [new rating system paper](https://arxiv.org/abs/2101.00400) will appear in the Web Conference 2021!**
If you're new to competitive programming, you may be wondering: what are ratings and colors? What do they mean?
As a contestant and now coach of the UBC team, I've taken enough interest in the subject to have developed my own rating system, Elo-MMR, which I might describe in a future blog post. For now, I want to talk about ratings more generally: what does it mean to achieve a certain rating or title? How concerned should you be with your rating and title? Might it be harmful to be concerned with them at all?
A Brief History of Contest Ratings
--------------------------------------
Contest rating systems can trace their heritage back to the [Elo system](https://en.wikipedia.org/wiki/Elo_rating_system). Elo was devised for 2-player games, with rating updates based on whether a player wins, loses or draws. Starting in 1960, it was adopted by the chess community ...
: be it to prepare for whiteboard interviews, to be exposed to ideas for
computer scienceresearch
76.
Llama Code: Open Coding LLM Llama Code in CP
==================
Today, Meta released Llama Code, a Large Language Model trained specifically for code. It's trained on Python, C++, Java, PHP, Typescript, C#, Bash. They are releasing 3 models with 7B, 13B and 34B parameters respectively. The smaller two allow for Fill-in-the-Middle.
It's free for research and commercial use, but obviously requires a solid amount of computing power if you want to run it locally.
You can read more about it here: [https://about.fb.com/news/2023/08/code-llama-ai-for-coding/](https://about.fb.com/news/2023/08/code-llama-ai-for-coding/)
I'd be interested in seeing if this becomes useful in CP. It seems like there's a lot of potential, specifically with code completion with Fill-in-the-middle. Imagine having vscode, hitting "F3", typing something like "SegTree with lazy prop, range set max, and range +=", and getting exactly the segment tree you need in two seconds.
I also think it may be useful because although LLMs are cur...
-Middle. It's free for research and commercial use, but obviously requires a
solid amount of, It's free for research and commercial use, but obviously requires a solid
amount of computing power
77.
Codeforces Global Round 16 (meme announcement) #**Приветики! ヾ(≧▽≦*)o**
###**This is a meme announcement, but it will be updated too**.
We are incredibly happy to invite you to a special (for us and, we hope, for you) event, [contest:1566]. It will be held on [contest_time:1566], rated for everyone of course! Feel free to participate!
<br/>
#####The problems were written and prepared by [user:shishin,2018-09-25] and [user:Artyom123,2018-03-11].
We chose the green color because it matches the **"Upvote"** button (cyan is fine too).
#####**You know what to do.**
<br/>
#### Huge Thanks and much Love
to great people who _contributed_ in the round creation
These people really deserve all the warm words and that green upvotes:
- [user:isaf27,2016-02-27], the one who did a lot of things for the round to happen, I just can't find the exact words to thank him orz
- [user:Shinchan01,2019-12-19], [user:Ziware,2018-09-23], [user:Kirill22,2018-08-18], [user:ijxjdjd,2019-08-25], [user:m371,2020-10-05], [user:A...
78.
Greeting and an interview with the legendary Gennady Korotkevich _Hi, Codeforces!_
My name is Una and recently I became a part of the Codeforces team. Unfortunately, I’m not a programmer, but I’m happy to help with other things.
For example, if you win a T-shirt, you'll receive a message asking you to update your personal information, and I do it. ;)
As a new person in this area, I am interested in all the news. Recently I read an interesting interview with the legendary Gennady [user:tourist,2019-06-15] Korotkevich on the ITMO news portal. The interview is dedicated to the victory in the “Science and Life” category of the "TOP 50. The Most Famous People of St. Petersburg" award of the Sobaka.ru magazine. Codeforces team join others in congratulating!
The editors of the portal allowed to share the article on the Codeforces pages (and we are very grateful for this). Original article published at [http://news.ifmo.ru/ru/university_live/achievements/news/8550/](http://news.ifmo.ru/ru/university_live/achievements/news/8550/).
Gennady doesn'...
research and give them to those who have spent their lives solving algorithmic
problems. Science isn’t
79.
Weird sorts #1 — LIS sort I like sorting algorithms very much, and I usually come up with weird ideas for sorting. Sometimes I wonder would those work properly, and now when I finally have the time from social distancing, I decided to start a series on my eccentric ideas — Weird sorts.
As an introductory problem for Dynamic Programming, you all probably know about the Longest Increasing Subsequence problem (LIS). But what if we apply this… to sorting? Today in the first blog of the Weird sorts series, I introduce to you… the LIS sort.
#### **Basic idea**
The core idea is to extract the LIS from the current array and repeat it until the current array is empty. It can be shown that this process always terminates, because there will always be a LIS that have a size of at least 1, thus at each pass, we will always take at least 1 element away from the array. In the implementation, we will first find the LIS of the array and separate the LIS from the rest of the array. We will then recursively perfo...
research and looking for proofs, especially about inequalities.
80.
[Tutorial]Simply talk about some string problems which can be solved by SAM ### Preface
This is not a profound academic research, this is just my own experience.
Hope it can help you.
### Background
Not long ago I was confused while solving a problem "CF547E Mike and Friends", because of its memory limit.
I used generalized SAM and merge segment tree to solve it, but i got MLE for too many times TAT.
### Pre knowledge
#### Segment tree merging
Segment tree merging can merge two dynamic open point weight segment trees in $O(n\log n)$ time.
#### SAM (Suffix Automaton)
SAM is a FSA (Finite State Automaton) that can maintain all suffixes of a string in $O(n)$ time and $O(n|\Sigma|)$ space, and support searching substrings.
Generalized SAM is SAM which maintains many strings. At first we set the root, and insert like common SAM. Additionally,pay attention to determine whether the current node already exists.
Create a suffix automaton for the reverse string,you can get the Suffix Tree.
So we use segment tree merging to modify t...
This is not a profound academic research, this is just my own experience.
81.
HFT Battle 2017 ### Hello Codeforces!
[HFT Battle 2017](http://hftbattle.com) is going on – the trading algorithms competition, in which every participant can try on an HFT researcher’s hat. The goal is to create a stable and profitable HFT algorithm by researching a market microstructure and a behaviour of the financial instrument. In May we will be hosting another 24-hour competition in code optimization and speeding up based on algorithms created during HFT Battle. We hope that Codeforces users will especially like this format :)
During the competition we provide you a set of real HFT-instruments for research and strategy analysis and real market data from one of the world’s largest exchanges. Same as last year, trading conditions are simplified compared to the real ones: there are lower fees and [round-trip](https://docs.hftbattle.com/en/HFAQ.html#simulator).
Also there are some significant differences from the previous competition:
- You are able to create your strategies both in C++ ...
for research and strategy analysis and real market data from one of the
world’s largest exchanges, During the competition we provide you a set of real HFT-instruments for research
and strategy
82.
Discussion: Modern G++ Command Line Hello Codeforces!
I am in the process of making improvements and updates to the judgment machines.
I've read the post https://codeforces.com/blog/entry/94587 and I think, maybe it is a good idea to make such a compilation line `-O3 -funroll-loops -march=native -mtune=native`?
I haven't done any research that it is definitely better than `-O2` and it is best in the general case for CP solutions.
In a way, this will only strengthen the gap from Python/PyPy/Java,
on the other hand: in pragmas and so you can set up everything.
What do you think? What are suggestions to the command line?
P.S. You got it right. Yes, `gcc11 std=c++20`, `pypy3 64-bit` and more are coming.
any research that it is definitely better than `-O2` and it is best in the
general case for CP, compilation line `-O3 -funroll-loops -march=native -mtune=native`? I haven't
done anyresearch that it is
83.
An awesome list for competitive programming! This is a project I started from late January 2016.
My motive is that: Although there's fantastic information out there, I think they're still spread all over the place. Therefore, in my opinion it would probably be cool if there's an [awesome list](https://github.com/sindresorhus/awesome) for competitive programming! ( *It's now featured on the main list!* )
I'm actively updating the list here: [https://github.com/lnishan/awesome-competitive-programming](https://github.com/lnishan/awesome-competitive-programming)
# Awesome Competitive Programming [](https://github.com/sindresorhus/awesome)
A curated list of awesome `Competitive Programming`, `Algorithm` and `Data Structure` resources.
Created with a view to connecting people to information, this list below contains a complete collection of all the fantastic resources I've collected over the course of my 11...
/index.html) | An international journal focused on the research and practice of
professionals who are
84.
Snackdown finals live commentary blog Hi All,
Final rankings of the contest.
Overall top 5 in onsite ranking
1. ancalagon from IIT Bombay consisting of [user:Balajiganapathi,2015-06-27] and Deepa Panwar
2. smack_down from Tower Research Captial consisting of Smit Hinsu ([user:Smit,2015-06-28]) and Siddharth Bora ([user:SiddharthBora,2015-06-28])
3. logicmonks_ from Google consisting of Akashdeep Nain ([user:akashdeep,2015-06-28]) and Nishant Redkar.
4. sandy_team from IIT Bombay consisting of Sai Sandeep ([user:harrypotter192,2015-06-28]).
5. believe_iiith from IIIT Hyderabad consisting of Pulkit Goel ([user:pulkitg10,2015-06-27]) and Vivek Hamirwasia ([user:viv001,2015-06-27])
Overall top 5 in final online ranking.
1. aapppppppiii from Tsinghua University having Apia Du and Yinzhan Xu ([user:xyz111,2015-06-27])
2. rake_compress from ITMO consisting of Gennady Korotkevich ([user:tourist,2015-06-27]) and Borys Minaiev ([user:qwerty787788,2015-06-27])
3. two_captains from Yandex consisting of Mikhail T...
ITMO (Saint Petersburg National Research University of Information
Technologies, Mechanics and, . smack_down from Tower Research Captial consisting of Smit Hinsu
([user:Smit,2015-06-28]) and, 1. ancalagon from IIT Bombay 2. smack_down from Tower Research 3. logicmonks_
from Google 4, Research Captial consisting of Smit Hinsu ([user:Smit,2015-06-28]) and
Siddharth Bora, Smit Hinsu and Siddharth Bora from Tower Research Captial
85.
Analyzing rating formulas In this post I'll try to expose the results of my research regarding the rating formula. More specifically, I'll show a graph that gives you a match rating according to your performance in a contest and some aspects of how ratings are updated. **This post is quite large, if you are only interested in the results you can easily skim through it :)**
[cut]
_Disclaimer_: I'll try to support my assumptions and assertions with data but, altough I have done the analysis carefully, I may have done a mistake :) Moreover, take into account that some of my formulas are approximations.
Motivation
==================
Almost two years ago I started to participate in contests more actively, aiming to be red one day. To increase my motivation I tried to find a formula that evaluated how well I did during a competition. At that time there were no API nor [user:DmitriyH,2015-06-21]'s statistics so I manually looked at a lot of profiles to try to find 'stable' points: users that didn't change...
In this post I'll try to expose the results of my research regarding the rating
formula. More
86.
HCW '19 Team Round Editorial This is an editorial blog for [contest:102279]. Any further question can be asked in the comments, I'll try to answer all the questions. Please, do not private message or email me, your question could be the same as others', and I really hate to answer one question multiple times. >:(
[problem:102279A]
------------------
Author: [user:low_,2019-07-22].
<spoiler summary="Tutorial">
To solve the problem, you'll only need to note that in $(N+1)$-th turn: Seo moved through exactly $(N+1)*V_s$ property, that is exactly $V_s$ full round of the board, so that he end up in $1$ afterwards. The same happens with B21 and Lowie. After that, the game keeps repeating itself.
We can conclude that: if there isn't any event of one paying other in the first $3*(N+1)$ turns, it will never happen, so we can output $3000000000$. Otherwise, we can find the first event of it by brute force in $O(3*(N+1))$ time complexity.
Maximum time complexity: $O(3*(N+1))$.
</spoiler>
[problem:102279B]...
First, we take a little research into the characteristics of a rooted tree (let
its root be node $1
Tutorial of HCW 19 Team Round (ICPC format)
87.
AtCoder Beginner Contest 151 English Solutions #A — Next Alphabet
The easiest way to deal with this problem is probably to convert the given character to an integer, add one, and convert it back. If you absolutely can't do that, a somewhat more annoying implementation would involve iterating through the alphabet, waiting until you find the given letter, using a boolean variable to store that the letter has been found, and printing the letter on the next iteration of the loop. (However, iterating over the alphabet is itself nasty unless you have conversion from letters to integers, so this approach is rather pointless unless your language just doesn't support the first method, though in that case you should probably switch languages anyway.)
Runtime: $O(1)$. [Click here for my submission.](https://atcoder.jp/contests/abc151/submissions/9440245)
---
#B — Achieve the Goal
In total, we need to earn $NM$ points. We subtract the points earned so far and determine whether this is a valid score for the final ...
internet already. Then, they should have done some basic research and, upon
realizing how easy it would
88.
Lexicographically Minimal String Rotation --------------------
--------------------
--------------------
--------------------
--------------------
# <strong> <center style="color:red;"> Table of content </center> </strong>
| Teleporter | Description |
| :---------------------------------------------- | :----------------------------------------------------------- |
| [I. The Problem](#problem) | Describe about the problem |
| [II. Bruteforce Approach](#brute) | Simple way to do the problem |
| [III. Hashing Approach](#hash) | Reduce circular substring comparing complexity |
| [IV. Sqrt Decomposition](#sqrt) | Divide into parts, solve each part then solve the whole part |
| [V. KMP Approach](#kmp) | Magical Linear Booth-KMP Algorithm ...
89.
Helping out in our NOI: Part 1 Now that the Philippine IOI team has been selected and this year's competition cycle is ending, I'd like to post a series detailing my participation in our national olympiad's organizing team this year. (I'm also doing this because my contribution is dropping! That's why it's a series, so I get even more contribution. I will do anything for imaginary internet points.)
This year, I helped write, make data for, and test problems for our national olympiad. I hope that you'll learn something about problemsetting or testing from this series. And if not, then I hope to introduce you to our olympiad's excellent problems. And if you don't find our problems interesting, then this post isn't for you and I'm sorry for wasting your time.
In this first part, I'll talk introduce our olympiad, the NOI.PH, and how I contributed to our elimination round. Here's a picture I made for the elimination round that will maybe convince you to read more:
Note th...
had to do research on the major news stories in the Philippines over the past
year. (I went on Reddit
90.
Invitation to the Bay Area Programming Contest on March 27th Hello Codeforces!
We are excited to invite you to the first ever Bay Area Programming Contest! The contest is open for everyone to participate, and will start on [Saturday, March 27, 2021 at 9:00<sup>UTC-7</sup>](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Bay+Area+Programming+Contest&iso=20210327T09&p1=1240&ah=4).
The contest was written by me, [user:pocafup,2021-03-25], [user:EndlessVoid,2021-03-25], [user:ant101,2021-03-25], and [user:NikhilC,2021-03-25].
There will be two divisions, the Novice division and the Advanced division. The Novice division is for participants with one year or less of programming experience and little to no contest experience, and the Advanced division is for everyone who doesn't meet that criteria. Each division will have 8 problems to solve in 4 hours. We will be giving out prizes totaling to at least 400 dollars for the top pre-college students in both divisions. This is an **individual contest**.
The contest will conducted in C...
contest to make sure you're familiar with Codeforces, and take this
opportunity toresearch and, this opportunity to research and test out fast i/o techniques in your
language. For the actual
91.
Yandex.Algorithm <img src="http://assets.codeforces.com/images/yandex-algorithm-en-logo.png" style="float:left;padding:0.5em;" img="">
<p>
We are glad to introduce <a href="http://company.yandex.com/general_info/yandex_today.xml">Yandex</a> open programming competition "Yandex.Algorithm" hosted by Codeforces. The competition starts on May 4th and will consist of
two qualification rounds, two online rounds and a final onsite round.
Some of the rounds are created by Yandex employees.
The onsite round will be held at the <a href="http://it-edu.mipt.ru/en.html">
Yandex Summer School in Distributed Computing</a><a> in </a><a href="http://phystech.edu/">Moscow Institute of Physics
and Technology</a>.
</p>
<p>
Any registered member of Codeforces can participate.
There will be 5 rounds, 2 hours each.
15 winners of the last online round will be invited to participate in the Summer School and in the
final round of Yandex.Open. 70 best participants will get T-shirts. [cut]</p>
<p>
The school...
and its applications to different areas, as well as to highlight the next
generationresearch, the next generation research directions. We will also provide a set of
practical problems and the
92.
CS Research Fields, and Intersection with Competitive Programming I was curious to ask the Codeforces community what they think of the current CS research fields, and how possibly mediocre people in competitive programming can fit in / contribute. I am trying to find / think of a research field that I could possibly work in, and find productive and possibly contribute in, that is accessible to those who are weak intellectually.
It is very discouraging for instance thinking about theoretical CS, as the people are so strong mathematically and otherwise, and then even I see lots of red people on CF who it seems never try or have anything happen research wise. So to me then it seems clear, if there are red people of CF who never accomplish anything research wise in theoretical CS, then for somebody like me the situation is beyond hopeless, and therefore that is not the field.
However the issue with more applied fields is that they seem somewhat less interesting at times, and there is a lot of very specific knowledge required. So far thinking abou...
CS Research Fields, and Intersection with Competitive Programming, have anything happen research wise. So to me then it seems clear, if there are
red people of CF who, I was curious to ask the Codeforces community what they think of the current CS
research fields
93.
Help needed to solve JOI 2013/2014 Problem — Historical Research Hi. I am having problem trying to solve JOI 2013/2014 — Historical Research. The english problem statement can be found [here](https://dunjudge.me/analysis/problems/743/).
For those who understand Japanese, the editorial can be found [here](https://www.ioi-jp.org/camp/2014/2014-sp-tasks/2014-sp-d1-historical-review.pdf)
The input and output data can be found [here](https://www.ioi-jp.org/camp/2014/2014-sp-tasks/2014-sp-d1-data.zip)
My approach is as follows:
Let $product = element \times frequency$ in subarray $[L,R]$
We use a BST to answer our max product queries and element updates efficiently, Each element of the BST would be $<product, element, frequency>$ and the elements in the BST are sorted by $product$.
Let $N$ be the number of elements in our array and $Q$ be the number of queries.
Perform square root decomposition on the queries by breaking them into $\sqrt{N}$ blocks and sorting them in increasing order of left bound followed by increasing order ...
Help needed to solve JOI 2013/2014 Problem — Historical Research, Hi. I am having problem trying to solve JOI 2013/2014 — Historical Research.
The english
94.
CodeChef June Cook-Off invitation Hello Codeforces!
I’d like to invite you to [CodeChef June Cook-Off] (https://www.codechef.com/COOK83) that will start at 21:30 IST of 18th June 2017 (check your time zone [here](https://www.timeanddate.com/worldclock/fixedtime.html?msg=June+Cook-off+2017&iso=20170618T2130&p1=44&ah=2&am=30)). There will be 5 problems and it will last 2.5 hours.
This is my second Cook-off, my [previous round](https://www.codechef.com/COOK73) was on august 2016 — at this rate my rounds are going to be called Alei yearly contests!
- Problem Setter: Alei Reyes [user:alei,2017-06-17]
- Primary Tester and editorialist: Hussain Kara Fallah [user:Deadwing,2017-06-17]
- Secondary Tester: Kacper Walentynowicz [user:Miyukine,2017-06-17]
- Mandarin Translator: Hu Zecong [user:huzecong,2017-06-17]
- Vietnamese Translator: Team VNOI
- Russian Translator : Sergey Kulik [user:CherryTree,2017-06-17]
No registration is required, anybody with a CodeChef handle can participate.
Hope you enjoy t...
**SNACKUP**: I came up with this problem while doing research on the double
cycle cover conjecture, research on the double cycle cover conjecture. The problem is about finding a
set of cycles such that
95.
Как я учился в бакалавриате ПМИ Питерской Вышки Привет, codeforces!
Меня зовут Миша, в этом году я закончил бакалавриат НИУ ВШЭ — Санкт-Петербург по специальности “[Прикладная математика и информатика](https://spb.hse.ru/ba/appmath/)” (ПМИ) и хочу поделиться своими впечатлениями.
Немного о себе: в школе я много решал задачи на codeforces, участвовал в олимпиадах и даже занял [третье место](http://neerc.ifmo.ru/school/archive/2015-2016/ru-olymp-roi-2016-standings.html) на РОИ 2016. Окончив школу, я хотел выбрать вуз, который поможет мне построить успешную карьеру в сфере IT. Я пообщался со старшими товарищами и решил поступать в Академический Университет, где на тот момент уже давно существовала прекрасная магистерская программа и два года как появилась бакалаврская программа, которой студенты были очень довольны.
Вышло так, что по окончании второго курса наша кафедра переехала из Академического Университета в петербургский кампус Высшей Школы Экономики. Все очень переживали, как пройдет этот переезд, но, к счастью, всё [сл...
защитил диплом и в сейчас продолжает работу над своим проектом в лаборатории
[JetBrainsResearch, исследователь из JetBrains Research [Денис
Степанов](https://research.jetbrains.org/ru/researchers, постажироваться в крупных компаниях: в Яндекс, JetBrains и JetBrains Research,
ВКонтакте; в Google и, простор для выбора темы научного-исследовательского проекта. JetBrains и
JetBrainsResearch, Яндекс, своим проектом в лаборатории [JetBrains Research
](https://research.jetbrains.org/ru/) под руководством
96.
Codeforces Deltix Round Autumn 2021 [Div.1 + Div.2] <a href="https://deltix.io/"><img alt="deltix" src="https://assets.codeforces.com/images/deltix/deltix-autumn-2021.gif" style="float:right; height: 400px"/></a>
<p>Hi, <span style="font-weight:bold">Code</span><span style="color:rgb(71,94,152);font-weight:bold">forces</span>!</p>
We are **[DELTIX](https://deltix.io/)**. Founded in 2005, DELTIX is one of the market leaders in software development for financial research and products for systematic and algorithmic trading. In 2020 DELTIX joined the EPAM family. Our mission is to turn promising ideas into breakthrough products fast.
We are experts in:
- aggregation, storage, and processing large volumes of time-series data
- data modeling
- testing and deployment of quantitative models
In our team we value such skills as:
- knowledge of algorithms
- high-performance coding
- low latency data streams processing
We are excited to announce that we have released [TimeBase Web Admin Community Edition](https://github.com...
development for financial research and products for systematic and algorithmic
trading. In 2020 DELTIX, software development for financial research and products for systematic and
algorithmic trading. In
97.
Constructor Open Cup 2023 Greetings Codeforces community!
<center>
<img alt="CU" src="https://codeforces.com/predownloaded/6f/7b/6f7bd7743d6846cfe3b792a194a5eafa53797a66.jpg" style="float:right; height: 250px; margin: 10px; max-width:50%;"/>
</center>
We are excited to announce the **Constructor Open Cup 2023**, our annual online programming competition organized by Constructor University and JetBrains.
**<font color="#008ce3">What is the Constructor Open Cup 2023?</font>**
Constructor Open Cup is an online contest organized by Constructor University and JetBrains, the global leading tool provider for developers, to promote interest in computer science, data science, software development, and software engineering. You'll have to race against the clock to solve real-life programming challenges.
Put your knowledge and skills to the test in this 4-hour competition and stand a chance to walk away with a **scholarship** for the Bachelor's degree in Data Science and Software Development at Const...
countries, and around 80 percent have moved to Germany to study. Research
projects at the, over 110 countries, and around 80 percent have moved to Germany to study.
Research projects at the
98.
A funny "Trick" for coding RMQ with segment tree First of all this "Trick" is **just for fun** and it's actually slower than the normal implementation of RMQ with segment trees so do not use it if the time limit is tight.
I did some research and couldn't find any similar blog but don't hesitate to inform me if this has been mentioned before, I'll delete this blog. So let's start!
Assume you have to perform two types of queries on an array:
<ol>
<li>Find a minimal ( or maximal ) element in a range.</li>
<li>Increase the elements in a range by a given value.</li>
</ol>
There are a lot of ways to do this but let's assume that you will code a segment tree with three basic functions:
<ol>
<li>A build function.</li>
<li>An add function which increases the elements in a given range by a given value.</li>
<li>A get function to find a minimal element in a given range.</li>
</ol>
Now this "Trick" is about getting rid of the get function ( or at least making it shorter ), assume you want to find a minimal element ...
implementation of RMQ with segment trees so do not use it if the time limit is
tight. I did someresearch and, I did some research and couldn't find any similar blog but don't hesitate to
inform me if this has
99.
How are Solutions Executed in an OJ? Hello Codeforces!
It's been long since I last had the fun of any serious programming(being all night awake with loud music on headphones and lots of snacks infront) due to admission studies. I'm missing it a lot. So after the exams are done I wish to improve MathMash a lot and also start a pet project of some sort. First thing that came to my mind is to build a small cute OJ. I'm aware that we have plenty of OJs already and they are more than enough helpful. So this project won't be of much use to anyone. But it'll be fun to design and build an entire OJ from scratch and also learn lots of new stuff along the way.
So I did a light research yesterday about what I might need to learn to build it. The first obvious thing needed is of course a way to execute submitted codes. I tried to go with the easiest option first: Using some third-party service/api so that I can give them the code and receive the output. But there doesn't seem to be any free option of this kind. Ideone used to p...
new stuff along the way. So I did a light research yesterday about what I
might need to learn to, I'm sure a lot of you have created an OJ or did some research on how to do so
in the past. Can you, So I did a light research yesterday about what I might need to learn to build
it. The first obvious
100.
April Fools Day Contest 2016: editorial I'm happy to see that this year there were 3 people who managed to solve all 7 problems! Unfortunately, only 1097 participants solved at least one problem, which is less than in 2014.
#### [problem:656A]
This problem asked to figure out an integer sequence from two samples and problem title. It turned out to be surprisingly hard, a lot harder than I anticipated. A quick search through OEIS shows that while there are a lot of sequences which have these two numbers in them, only one is related to Leonardo da Vinci (and if you're looking for da Vinci, there are only two sequences overall). http://oeis.org/A221180 is an erroneous series of powers of 2, written down by da Vinci in his diaries and available as part of "Codex Madrid I".
#### [problem:656B]
Just one word: [typoglycemia](https://en.wikipedia.org/wiki/Typoglycemia).
[cut]
The urban legend (unsupported by any known research) claims that people can easily read text even if letters in each word are scrambled, as lo...
legend (unsupported by any known research) claims that people can easily read
text even if letters in
Tutorial of April Fools Day Contest 2016
101.
Новости Факультета Компьютерных Наук ВШЭ В этом году первый набор [Факультета Компьютерных Наук](http://bit.ly/25msmZi) заканчивает второй курс, и на этом фундамент, обязательный для всех, почти заканчивается. Что же ждет их дальше, на 3-4 курсе и в магистратуре? Ниже я расскажу об этом, а также об основных новостях [ФКН](http://bit.ly/25msmZi): старт специализаций, новая магистерская программа, открытие двух лабораторий, изменения в базовой программе 1-2 курса по итогам первых двух лет существования [ФКН](http://bit.ly/25msmZi), включая оценки и фидбэк от самих студентов.
**UPD.** Льготы по олимпиадам опубликованы [здесь](https://ba.hse.ru/data/2016/06/01/1130397875/Москва.pdf), а про всероссийские олимпиады написано [здесь](https://ba.hse.ru/olimp2016).
На 3-4 курс все студенты выбирают себе специализацию. Это набор курсов в рамках одной широкой темы, некоторые из которых обязательны для всех, кто выбрал специализацию, а из остальных нужно выбрать определенное количество (не все). Всего у нас будет пять специализаций,...
Есть предварительные договоренности о визитах профессоров из [Microsoft Research
](http
102.
SIT & JUB STAR Contest 2022 <center>
<img alt="SIT" src="https://codeforces.com/predownloaded/b7/59/b7597e61079718f49f275cfc2b343e9c1461bb78.png" style="float:right; height: 250px; margin: 10px; max-width:50%;"/>
</center>
Hello, Codeforces!
We are thrilled to announce the dates of our annual online programming competition, the **SIT & JUB STAR Contest 2022**, organized by the Schaffhausen Institute of Technology (SIT) in Switzerland and our partner Jacobs University Bremen (JUB) in Germany.
Winners will have the chance to receive exciting prizes, including a full scholarship for
**Master in Computer Science and Software Engineering** program.
**<font color="#00a987">What is the SIT & JUB STAR Contest?</font>**
The goal of the SIT & JUB STAR Contest is to promote interest in the field of Computer Science and Software Engineering, giving participants an opportunity to demonstrate their knowledge of programming. It is also a winning ticket for full scholarship to a master program. To partici...
comprised of a non-profit component, with education and research, as well as
commercial technology spin, education and research, as well as commercial technology spin-offs, consulting
services, a start-up, learning models. With a research-centric approach and an entrepreneurial
mentality at its core, the
103.
Feature Request: Support for embedded Facebook Livestreams on Codeforces, like Twitch or Youtube Context
------------------
Codeforces currently supports embedded Youtube and Twitch livestreams. Hacker Cup Finals is streamed only to Facebook, but I imagine there are lots of people who would like to watch it [or at least would like to know about it] on Codeforces. Unfortunately, it seems unlikely that Hacker Cup would be streamed to Youtube or Twitch in the foreseeable future.
Implementation?
------------------
It looks like embedding the stream is as simple as using an iframe, from the little research that I've done on [this page, which is about a church for some reason](https://churchcommunications.com/how-to-embed-facebook-live-on-your-website/).
I don't know how Codeforces implements this integration, but if it is with an iframe, it might be as simple as a third case to the supported stream link regex.
Why should Codeforces want to add Facebook Livestream support?
------------------
Because Hacker Cup is a big-name programming contest. If Codeforces wants to co...
iframe, from the little research that I've done on [this page, which is about
a church for some reason, the little research that I've done on [this page, which is about a church for
some reason](https
104.
Codeforces Deltix Round Spring 2021 [Div.1 + Div.2] <a href="https://deltix.io/"><img alt="deltix" src="/predownloaded/9c/ed/9ced30bc043cfa5c6928d46ec78c7c77ac87b0a8.png" style="float:right; height: 150px; "/></a>
<p>Hi <span style="font-weight:bold">Code</span><span style="color:rgb(71,94,152);font-weight:bold">forces</span>!</p>
We are **[DELTIX](https://deltix.io/)**. Founded in 2005, DELTIX is one of the market leaders in software development for financial research and products for systematic and algorithmic trading. In 2020 DELTIX joined the EPAM family. Our mission is to turn promising ideas into breakthrough products fast.
We are experts in:
* aggregation, storage, and processing large volumes of time-series data
* data modeling
* testing and deployment of quantitative models
In our team we value skills like:
* knowledge of algorithms
* high-performance coding
* low latency data streams processing
[Learn more about DELTIX]( https://deltix.io/)
Throughout the year, once per quarter, we will be invi...
development for financial research and products for systematic and algorithmic
trading. In 2020 DELTIX, software development for financial research and products for systematic and
algorithmic trading. In
105.
FAQ про факультет компьютерных наук в ВШЭ Проведя много встреч и личных бесед с абитуриентами, преподавателями, родителями, мы поняли, что часто отвечаем на одни и те же вопросы про новый факультет, и хорошо бы донести эти ответы до всех.
**Важные апдейты** 1. Принимать окончательное решение о своем выборе можно вплоть до конца июля, так что есть еще месяц на раздумья. 2. Если к нам подадут заявления люди, имеющие право на поступление без экзаменов в количестве большем, чем изначальное количество бюджетных мест, то нам расширят набор, увеличат количество бюджетных мест, и мы возьмем всех этих людей, т.к. мы просто обязаны это сделать.
**Q1. Чем программа обучения будет отличаться от ВМК?**
A1. В первую очередь, можете посмотреть саму программу [здесь](http://cs.hse.ru/ami/about) и почитать о [преподавателях](http://cs.hse.ru/ami/faculty). Программа будет отличаться и организационно, и содержательно. Организационно, не будет стандартных сессий, к которым нужно все заботать за несколько дней, ничего не делая весь преды...
групп на ФКН, а среди них есть группы в MIT, Ecole Normal Superior, Zurich
ETH, MicrosoftResearch
106.
Scaler Academy Review with Proof Hello community, I am one of the ex-Scaler students from the April Batch. I got a job from Campus Placement and I got only one referral in the entire one year. Sadly, I need to pay them, hence I wanted to make people aware of some facts backed with proof, so that they do-not fall into this trap. I have seen a lot of things written about Scaler in the recent month. Scaler came out in public with a video on "[What we do and Why we do](https://www.youtube.com/watch?v=faGIKYparWA&t=14s)", where they said their curriculum is focused on learning and not on jobs. But they end up getting disappointed, like most of us in our did.
In India, rarely people will come out in open to speak, because no-one wants to risk their future, so do I. People join such courses thinking that we do not need to pay now, we will pay when we get job. Hence they just join without giving it a second thought. But the main disappointment starts when you start paying installments for 24 months without getting any ...
June batch for Uber, Booking.com, Netflix, Google, Facebook, Tower Research
etc?
107.
Science for Ukraine Many research labs around the world are offering to host students and researchers affected by the war in Ukraine so they can continue their studies (more than 700 labs signed up so far from all fields of science): [https://docs.google.com/spreadsheets/d/1HqTKukfJGpmowQnSh4CoFn3T6HXcNS1T1pK-Xx9CknQ/edit?usp=sharing](https://docs.google.com/spreadsheets/d/1HqTKukfJGpmowQnSh4CoFn3T6HXcNS1T1pK-Xx9CknQ/edit?usp=sharing)
I can also connect you to research groups at our Computer Science department at ETH Zurich that offer several positions with funding covering all costs (travel, accommodation, living costs). Offers are internships for undergraduate or graduate students, research visits, PhD or PostDoc positions in various topics such as machine learning, computer vision, theory, security, systems, etc.
It would be great if you could share this information further to increase chances of helping someone!
More resources:
[https://scienceforukraine.eu/](https://scienceforukraine.eu/...
I can also connect you to research groups at our Computer Science department at
ETH Zurich that, Many research labs around the world are offering to host students and
researchers affected by the
108.
Some Reflections [Cross-post from AoPS] Hey Codeforces,
I made a [post](http://artofproblemsolving.com/community/c5h1266176_some_reflections) on AoPS that I thought you guys might find interesting. The original context was math contests in the US, but I think much of it applies to CS (and more generally) too.
-----
Hey AoPS, it’s good to be back. I’m feeling a little sentimental right now, but I guess that’s alright—it’s been six years since I first found you, and it’s been a long journey since. I was a sixth grader then, just starting Mathcounts, unsure if I’d even make the school team. I fell in love with For The Win! (Alpha) and played it during lunch break, after school, even the morning before Mathcounts Nats. In ninth and tenth grade, I scoured the Olympiad fora, wondering if there existed some magic advice that could propel me all the way to MOP. I was chasing after the mathematical footsteps of my Exeter friends then, always feeling a few steps behind. And now I’ve graduated high school. Contests are over fo...
that, especially if math is your thing. However, people also get into college
forresearch, crew
109.
What If... Virtual Contests were REAL? [cfscripts] Hey everyone!
With inspiration from
* the great [research](https://codeforces.com/blog/entry/86596) by [user:galen_colin,2022-06-25].
* [user:MiuraMiuMiu,2022-06-25]'s [Codeforces Anytime](https://codeforces.com/blog/entry/83122).
* ... and of course the various Codeforces performance predictors!
I proudly present **cfscripts**. *cfscripts* is a collection of scripts for Codeforces that uses the [cf-API](https://codeforces.com/apiHelp) to do different things.
For instance, *cfscripts* includes a script named **What If?** (yes, very fancy), which allows you to **simulate Codeforces contest rating changes** over time, but **including virtual and unofficial contests**.
You can choose to include only positive rating changes (this feature is dedicated to [user:galen_colin,2022-06-25]).<br/>
You may ask: *...
* the great [research](https://codeforces.com/blog/entry/86596) by
[user:galen_colin,2022-06-25
110.
Sorting and comparing 2D points in counter-clockwise order I have now bumped into several geometry problems that require clockwise 2D point sorting relative to a specific center, [here](https://www.codechef.com/DEC17/problems/REDBLUE/) is an example. The key to solving this task is to implement a comparator function, with this header:
~~~~~
bool operator<(const Point &a, const Point &b);
~~~~~
The function should return true iff _Point a_ goes before _Point b_ in counter-clockwise order (with a defined center-point).
If we correctly implement this function, we can do countless things, such as sorting points, handling sets and maps of points, applying binary search, etc.
I have researched and found out there is not really a simple, short, easy-to-remember implementation for this function out there. That's why I decided to share mine in this blog.
First of all, you obviously need a _Point_ template. If you aren't familiar with this, read [this](http://codeforces.com/blog/entry/48122) blog.
I only included dot product and z-c...
111.
Microsoft Q# Coding Contest – Summer 2020: editorial The contest is over; I hope you enjoyed it and learned something new in the process!
Here are the solution descriptions. You should also be able to see the solutions of the contest participants, and the discussions in the comments offer a lot of insight.
## A: "Distinguishing Unitaries" problems
### [problem:1357A1]
Let's consider the effect of these gates on the 2-qubit basis states, similar to how we did in [problem:1356A5]. We'll see that applying $\text{CNOT}_{12}$ and $\text{CNOT}_{21}$ to any of the basis states other than $|00\rangle$ yields different results.
[cut]
For example, $\text{CNOT}_{12} |01\rangle = |01\rangle$ and $\text{CNOT}_{21} |01\rangle = |11\rangle$. Thus, the easiest solution is: prepare two qubits in the $|01\rangle$ state and apply the unitary to them, then measure the second qubit; if it is still One, the gate is $\text{CNOT}_{12}$, otherwise it's $\text{CNOT}_{21}$.
```c#
operation Solve (unitary : (Qubit[] => Unit is Adj+Ctl)) : Int...
most areas in quantum computing, is a topic of active research. The library
used in these problems
Tutorial of Microsoft Q# Coding Contest - Summer 2020
112.
TeamsCode Spring 2023 Contest Hello Codeforces! [TeamsCode](http://teamscode.org) is excited to announce the [TeamsCode Spring 2023 Virtual Programming Contest](https://www.teamscode.org/contests/spring-2023)! It will take place on [April 2nd, 2023 at 9:45 AM PST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=TeamsCode+Spring+2023+Contest&iso=20230402T0945&p1=1239&ah=3).
**Teams of up to 4 members will have 3 hours to solve around 10 problems.** There are two divisions: Novice and Advanced, so no matter what skill level you are, there is a place for you.
The guest speaker events will feature **Dr. Subho Majumdar**, a technical leader in applied trustworthy machine learning who believes in a community-centric approach to data-driven decision-making, and **Dr. Jane Bae**, an Assistant Professor of Aerospace at the Graduate Aerospace Laboratories at Caltech. She received her Ph.D. in Computational and Mathematical Engineering from Stanford University in 2018. She was a postdoctoral fellow in the Grad...
Harvard University before joining the Caltech faculty. Her main research
focuses on computational fluid, . Her main research focuses on computational fluid mechanics, in particular on
modeling and control
113.
Correlation between POLITICAL VALUES and RATING? Hello Codeforces,
Today, I wanted to make a blog to identify a possible link between **political orientation** (on the traditional left to right scale) versus **Codeforces rating** (influenced from [this blog](https://codeforces.com/blog/entry/99589)).
#### Notes on the [Political Spectrum](https://en.wikipedia.org/wiki/Left%E2%80%93right_political_spectrum)
The political terms left wing and right wing (which comprise the modern political spectrum) originally started as a reference to politicians’ seating arrangements in the French National Assembly during the French Revolution.
**Left wing** beliefs are liberal in that they believe society is best served with an expanded role for the government that aligns with progressive policies furthering social, economic, and environmental justice. These include entitlement programs such as social security, healthcare reform, welfare systems, and other social safety nets. The expanded social role of government also includes protections...
- _Pew Research Center_: [Political Typology
Quiz](https://www.pewresearch.org/politics/quiz, Research Center_: [Political Typology
Quiz](https://www.pewresearch.org/politics/quiz/political-typology
114.
Educational Codeforces Round 140 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1767] [contest:1767] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-12-15] Dalabaev, Vladimir [user:vovuh,2022-12-15] Petrov, Ivan [user:BledDest,2022-12-15] Androsov, Mak...
processing media data;_ - _Conduct research in the field of Computer Vision:
classification, , the logic of scenarios for processing media data;_ - _Conduct research in the
field of Computer
Announcement of Educational Codeforces Round 140 (Rated for Div. 2)
115.
[Blogpost] Indian ICPC 2019 Experience Hi everyone,
I started writing a blog on my experience at the Indian ICPC Regionals of 2019-20 (the previous season as of this post) slightly more than a year back [here](https://codeforces.com/blog/entry/76290). I stopped after 2 blogposts due to various reasons: World Finals not happening, our team losing interest in CP in general, and I kind of wanted to finish the series after the whole season arc was completed. With both my teammates retiring before this season and World Finals finally looking possible in October, I decided to revive it, so I would be able to publish a final post after WF and be done with this season :D. This seemed like the best time to post, since Amrita regionals has it's online round on 10th July, so many teams would probably be up-solving old regionals, and it might be interesting to compare how you performed vs how we did in the contest setting — what mistakes we made, and what you should avoid. It's also a nice way to preserve my memories, and to h...
"Research as an undergrad", "Applying to top MS programs in the US", "Why I
think Anime is amazing, I wanted to talk about in my blog; such as "Research as an undergrad",
"Applying to top MS programs
116.
Bayan — live coverage Hi everybody, it's 11:10 local time at Tehran, I'll tell you how the Bayan Programming contest 2013 (1391) onsite Finals is progressing.
**22:17**. Peter50216, cerealguy and Egor are top-three! Congratulations!
**22:05**. Closing ceremony. The rejudge took place for one problem.
**18:30**. Not everything of Funkoders has been judged yet, so the results of this additional fun contest will come later.
**18:29**. **It's over!**
**18:27**. Announcement: two minutes to the end of the contest. It should have 5 though.
**18:10**. It's a fun competition, so there are two guys entertaining competitors and spectators:
**18:04**. Every couple of minutes one of the baloons exploid, making a person next to it jumping up.
**17:54**. Only the first submission will count. There are 15 problems. Competitors hope that the problems are not harder than in the main round.
...
my nano-research on how it works (can also be read as "IT works") in Iran. Or
just [look at the
117.
MNM Cheating Algorithm MNM algo
==================
Once upon a time, three Syrian competitive programmers decided to spend their time in doing research and studies. they worked hard.
Finally, hard work paid off and they discovered the algorithm -which Codeforces uses to catch cheaters [the ones who violate Codeforces contest rules]. Their lives have just become easier and now they can copy codes from each other / Ideone without spending time changing variables names and methods declarations order.
Those three inventors are [user:Math_Master,2018-02-24], [user:NourAlhadi,2018-02-24], [user:Mr.spring,2018-02-24]. (hats off people ...).
MNM -(first letters of [user:Math_Master,2018-02-24], [user:NourAlhadi,2018-02-24], [user:Mr.spring,2018-02-24] respectively)- Cheating Algorithm is -in my opinion, the greatest since the invention of breadth/depth-first search algorithms.
MNM is simple, here is a simple explanation for it:
------------------
- MNM relies on "divide and conquer" approach in solvi...
research and studies. they worked hard. Finally, hard work paid off and they
discovered the algorithm
118.
Two-liners for triangle centers using Barycentric coordinates Recently, I created a [blog entry](http://codeforces.com/blog/entry/22175) about using C++ `std::complex` as an alternative to points for computational geometry. We will now apply this technique for more geometry for C++!
Triangle centers are important for they create a connection between triangles, circles, and angles in geometric construction. But the classical way to determine them is a little hassle to either derive, or code.
For example, we can get the circumcenter by constructing two perpendicular bisectors and intersecting them. [Math for dummies](http://www.dummies.com/how-to/content/how-to-find-the-incenter-circumcenter-and-orthocen.html) provides a brief explanation of some triangle center formulae if you want to know what I'm talking about.
But can we generalize the way to get ALL kinds of triangle centers?
Barycentric Coordinates
-----------------------
Barycentric coordinates uses a kind of coordinate system through three vertices of the triangle as basis. ...
buy it in a bookstore. If you also found some research papers that look
useful, I would also like
119.
Teams going to ACM-ICPC World Finals 2019 Completed List! [user:Luqman,2019-01-30] said he [isn't creating a chart](https://codeforces.com/blog/entry/64899?#comment-488294) of teams going to ACM-ICPC this year as he isn't competing, so I added in all the teams. Let's complete the table together!
For the teams where I don't know the cf handles of the team members, I put their names instead.
Europe
======
| Count | Country | Region | University | Member 1 | Member 2 | Member 3 |
| ----- | ------- | ------ | ---------- | -------- | -------- | -------- |
| 1 | Romania | SEERC | Alexandru Ioan Cuza University of Iași | [user:Juve45,2019-01-31] | [user:Cristian1997,2019-01-31] | [user:Sin,2019-01-31] |
| 2 | Switzerland | SWERC | ETH Zürich | [user:TimonKnigge,2019-03-08] | [user:zaspagety,2019-03-08] | Stefanie Zbinden |
| 3 | Netherlands | NWERC | Leiden University | [user:pimsp,2019-03-08] | Onno Berrevoets | Daan van Gent |
| 4 | Ukraine | SEERC | National Technical University "Kharkiv Polytechnic Institute" | [user:vlad8,2019-02-0...
| National Research University Higher School of Economics |
[user:qoo2p5,2019-01-31] | [user:super_azbuka
120.
[Tutorial] The Floyd-Warshall algorithm and its generalizations **TL;DR**
- The Floyd-Warshall algorithm is a special case of the more general case of aggregation over paths in a graph — in this blog, we look at a few examples and point to some references for further study.
- The algebraic path problem constitutes a family of problems that can be solved using similar techniques.
- [This](https://academic.oup.com/imamat/article-abstract/15/2/161/642786) and [this](https://academic.oup.com/imamat/article-abstract/7/3/273/1017970) paper develop the theory of semirings in this context, and <a href="https://page.mi.fu-berlin.de/rote/Papers/pdf/A+systolic+array+algorithm+for+the+algebraic+path+problem+(shortest+paths;+matrix+inversion).pdf">this</a> treats some computational aspects of it.
- [Kleene algebras](https://en.wikipedia.org/wiki/Kleene_algebra) are what end up being used in most of the examples given here, but semirings are more general structures.
- While not discussed in the blog post, the idea of a [valuation algebra](https://on...
/2105.10386.pdf) is a great reference on some parts of research happening in
this field. 3. **Kleene's
121.
Free USACO Mock test on Jan 21st Hi everyone,
X-Camp Academy will provide a **free USACO Mock test** on Jan 21st, 4 PM-8 PM pacific time. Open to all, free.
A brief introduction to X-Camp (x-camp.org): A silicon valley based institute focusing on foundation buildup for the majority of students, and competitive programming for students who are passionate about competitions. Systematic curriculum from beginner to master class level. Nearly 20 USACO Platinum division contestants in the past 2 years. 5 students entered US National Camp in the past two years and two current students are among the top 10 from 22/23 Season Dec Platinum Division.
**Some highlights: **
a. Problems arranged by X-Camp Academy teaching research team and catching the newest USACO problem trends.
b. Simulation of a real competition environment. Best preparation for what’s to be expected for the coming USACO contest in late Jan (Jan 27 to Jan 30).
c. Covering Bronze to Platinum levels.
**Registration Link:** https://docs.google...
a. Problems arranged by X-Camp Academy teaching research team and catching the
newest USACO problem, research team and catching the newest USACO problem trends. b. Simulation of a
real competition
122.
Introducing Egor Kulikov as World Finals 2013 official blogger Hi there!
This is the first post in the ACM ICPC World Finals official blog. This year [Yandex](http://about.yandex.com/) is the local partner of the World Finals host — Saint Petersburg National Research University ITMO. We have a lot of former ICPC finalists working at Yandex, and some of them including me will work as analysts during the World Finals contest. Let me introduce my friend [user:Egor,2013-06-20] Kulikov from Yandex in Saint Petersburg, who will be the ICPC blogger. I am more than sure that he will provide an expert coverage on different aspects of the World Finals, and that's why.
First and foremost, he was my teammate in the Moscow State University team for the World Finals 2007 in Tokyo, where we took bronze, so he knows everything from the inside. We had trained for five years to get there. The competition at MSU is always very strong, so in our case we basically had to win NEERC 2006 just to outrun our main rivals from the same university. They had alr...
National Research University ITMO. We have a lot of former ICPC finalists
working at Yandex, and some, Research University ITMO. We have a lot of former ICPC finalists working at
Yandex, and some of them
123.
Yandex.Algorithm Online Round 1 Analysis In the first online round of Yandex.Algorithm competition 609 participants submitted at least one solution and 396 submitted at least one correct solution. Problems _Non-Squares_ and _Kingdom Division_ were fairly easy, both resulted in approximately 300 correct submissions. Problem _Stacks of Coins_ was moderately easy and was solved by 145 participants. The three other problems proved to be more difficult. _Stickers_ could be a very challenging string problem, but small input size allowed for dynamic programming solution, which 22 contestants got right. _Assistants_ was solved by 13 participants; it required binary search, greedy, and some basic data structures to get it under time limit.During the contest, nobody was able to solve _State Roads_, which was a neat graph-theoretical problem with a simple to code, but a quite tricky solution.
Congratulations to [user:Kenny_HORROR,2013-07-15] who was the only one to solve five problems, and to [user:Petr,2013-07-15], [user:tourist,20...
$ research tasks can be completed. The $i$-th task can be executed by the
professor using $p_i
124.
That's Great..... **SORRY FOR MY ENGLISH. HOPE YOU WILL STILL UNDERSTAND THIS.**
Hello Codeforces,
I have researched on google and some others on Competitve Programming Topic. Now, I have got some awesome resources that helped me, hope will help you too. I want share the resources with you.
### **Some Great Blogs Are:**
|Name(Handle) |Blog |Description|
|-------------------|---------|-----------|
|Codeforces|[Codeforces Blog](http://codeforces.com/)|A awesome blog for help. If you are stuck anything on CP and ask on Codeforces Blog, I can surely tell you won't be disappointed. There are lots of guys who will help you.|
|Petr Mitrichev ([user:Petr,2020-06-19])|[Algorithms Weekly](https://petr-mitrichev.blogspot.com/)|A good blog for learning CP topics, Contest discussions.|
|Makoto Soejima ([user:rng_58,2020-06-19])|[rng_58's blog](https://rng-58.blogspot.com/)|A sometimes older Blog. But it still good for learning Algorithms and Data Structures|
|Bruce Merry ([user:bmerry,...
125.
Invitation to join the UP ACM Algolympics 2023 Final Round Mirror at the Codeforces Gym Hello, Codeforces friends!
I'd like to invite you to the mirror of the UP ACM Algolympics 2023 Final Round. Algolympics is an annual contest organized by the Association for Computing Machinery, University of the Philippines Diliman Chapter. It is open to teams consisting of undergraduate college students from the Philippines. This year's contest was held on March 25, 2023, but the mirrors are open to everyone!
**Contest details:**
- There are 13 problems over 5 hours.
- Every problem is worth 1 point.
- Scoring is binary. There are no partial points.
- The penalties are ICPC-style.
- The mirror will be held on June 17, 2023, from 9:00am to 2:00pm (UTC+8).
- [Click here to go to the gym contest](https://codeforces.com/gym/104435)
Please register at [the gym](https://codeforces.com/gyms) to join the mirror.
The problems range from easy to challenging. Everyone from the newbie to the grandmaster should find an interesting problem in the contest.
The problem setters...
some of his colleagues in Samsung Research. Thanks to
[user:MikeMirzayanov,2023-06-16] for, :1NCID3R,2023-06-16]) and some of his colleagues in Samsung Research. Thanks to
[user:MikeMirzayanov,2023
126.
The CROC All-Russian Open Programming Championship Results Last Friday, on May 17, CROC finishes the All-Russian Open Programming Championship. The CROC company (together with Codeforces) holds a competition for the best coders of our country for the second year in a row.
Informational technologies are a dynamic habitat where the best minds dwell and sometimes innovative ideas come up at a great speed! This time the organizers stated that the championship is all-Russian but they were surprised to see the championship interest extending beyond the national border.
<center>
<img src="http://lh3.googleusercontent.com/-bHHNR_A6z6k/UZpYlF2ElYI/AAAAAAABDVs/OlIAHRayouI/s560/90520.jpg"/>
</center>
<i>The interest towards the competition was such that we had many participants from Russia, former Sovyet republics and even far away countries. On this championship, coders solve sports programming problems: to win, they need to come up with effective algorithms, code them quickly, consider all non-typical situations. Besides, there is the additi...
Gennady Korotkievich, a student of St. Petersburg National Information Research
Institute of
127.
rpeng's definition of 'good' problems If you still need to gain things from contests (e.g. I got into contests in high school mainly because Waterloo promised to pay my undergrad tuition if I bring some metals, and did WF so I could go to the US): unless the problem setters have very poor academic integrity and are also very very very good friends with you, there is no such thing as good or bad problems: there are just problems that you lose to, and problems you don't lose to. I'm saying this because the back-end of contest organization is usually held together by spit-and-glue, so to make it through such system, one essentially has to prepare for worst-case scenarios.
If you are getting into contest organization, the one sentence criteria I like to use is "achieve the intended score distribution, while maximizing the amount of additional information that one needs to communicate to someone who didn't solve the problem so they solve it". This in my experience minimizes the amount of post-contest complaining, and gives c...
turning research papers into problems. Should such escalation occur, you (or
your coach) need to be very, -syllabus/ioi-syllabus.pdf), because otherwise the escalation is towards turning
research papers into
128.
How does IT work in Iran. Part 1 I took this chance being in Tehran to learn more about professional life of an IT specialist in Iran. This path actually starts in the school, continues at the university followed by a professional career.
Here is the first part of my research, it is an interview with Mr. Ali Ghadiri, the founder and CEO of Bayan. Being not only an IT-entrepreneur, but also serving as a school teacher for over 10 years, he provided information on educational system of Iran as well as about job situation.
Education
---------
**How is the educational system organized in Iran in general? E. g., does one have to pay for school or university?**
Ali Ghadiri: Both paid and free-of-charge models co-exist.
The best schools, especially high schools, are not free. Besides entirely private schools, there are semi-government ones, where you have to pass entrance exams. They are called “sampad” and exist in many cities in Iran, in Tehran there are about 10 sampads for boys and 10 for girls _(Comment ...
Here is the first part of my research, it is an interview with Mr. Ali Ghadiri,
the founder and CEO
129.
Why so less "RED" coders in India? I really admire the names in the "—>Top Rated" section on the right side of the page. But to see that their is no Indian in those names hurts a little. I know India has a strong mathematical heritage and it should have been reflected in the particularly new paradigm of Computer Science also, but sadly it doesn't. So, what do you guys think are some reasons that Indians don't have any coders in not only Top 10 but also none in Top 100?
[cut]
I didn't particularly research on this topic but here are some reasons I can think of.
- Most of the people who start CP is because of Jobs. I don't think there is anything wrong with it but this type of motivation won't take anyone far. Indians become Candidate Master or Master and stop CP completely after getting a job.
- Due to almost 0 coding culture in high schools. Well a typical Indian starts coding in college(most people in 2nd year to be honest) and considering they have 3-4 years to do CP, I don't think many people can become a "RE...
not only Top 10 but also none in Top 100? [cut] I didn't particularly research
on this topic but, [cut] I didn't particularly research on this topic but here are some reasons I
can think of.
130.
Advanced Algorithms and Complexity Course I [wrote](http://codeforces.com/blog/entry/44924) in May about the launch of [Data Structures and Algorithms](https://goo.gl/jV5fbe) Specialization at Coursera. In September, the [Advanced Algorithms and Complexity](https://goo.gl/TalA42) Course of this Specialization was launched, and I'd like to tell you more about it.
Course topics:
1. Network Flows (Ford-Fulkerson and Edmonds-Karp algorithms).
1. Linear Programming (the Simplex Method).
1. NP-completeness (theory, reductions, solving NP-complete problems using SAT-solvers).
1. Coping with NP-completeness (bruteforce optimizations, solvable cases, approximation algorithms).
1. Streaming Algorithms.
The problems for this course were prepared by [user:ifsmirnov,2016-10-03], [user:Ilyakor,2016-10-03], [user:Michael,2016-10-03], [user:Perlik,2016-10-03], [user:romanandreev,2016-10-03], [user:Zlobober,2016-10-03] and Paul Melnichuk.
Network flows and the algorithms covered in the Specialization can sound as not very advan...
problem to a SAT instance, and then it turns out modern SAT-solvers based on
the latestresearch, -solvers based on the latest research advances can solve huge instances in
practice. Streaming
131.
Slides from my BubbleCup presentation: "How to extract maximum value out of competitive programming?" Last week there was a [BubbleCup contest](http://codeforces.com/blog/entry/19957), where I was invited as a guest and gave a presentation. AFAIK the presentation was recorded, but I have no idea if it's going to be released (or when). The presentation itself, is probably the worst presentation I ever gave. I talked mostly about how confusing it's going to be, but I was the one confused there :)
Anyway, here's the [link](https://www.dropbox.com/s/h4urgpxldfdp00y/Psyho%20presentation.pdf?dl=1) to the slides. I still think it might be useful for some people, since it touches something that is very rarely talked about. The presentation itself was made to counterbalance all of the simple answers to the old question of "How to get better in competitive programming?".
My main points (that I don't think were made clear enough):
- It's better to train to be an all-rounder than to have a narrow specialization. Especially in the long-term. People very often change the area of interest. ...
do your own research effectively., . You may feel lost without a coach, but that's how you'll learn to do your own
research effectively
132.
About think-cell <a href="https://www.think-cell.com/codeforces"><img src="https://assets.codeforces.com/images/think-cell.svg" align="right" style="height: 100px;" alt="text"/></a>
> Thank you, think-cell, for sponsoring the Standard C++ Foundation and challenging our Microsoft compiler team with complex C++ code.
>
> Herb Sutter, President of the Standard C++ Foundation
[think-cell](https://www.think-cell.com/codeforces) is a fast-paced software company in Berlin, Germany, with a focus on developing graphics products that stand out from the crowd. More than 1,000,000 users world-wide rely on [our software](https://www.think-cell.com/en/product) for their daily business as it makes creating graphical presentations so much easier, faster and more enjoyable. Among our customers are many renowned consulting companies and large international corporations.
We do not have to make compromises with regard to code quality and beauty, because think-cell is highly profitable. We are willing to go the ...
relationships with universities and research institutes across the U.S. and
Germany.
133.
On the direction of competitive programming Well, let's suppose this is not a rant but yes. Lately, I was feeling stupid. It feels like I'm becoming more and more stupid due to my performance in contests.
I should try not to blame the contests but rather myself. However, I feel like there are reasons that I'm bad at this. I'm going to explain my views through this piece of text. Personally, as one of the TAs (of national IOI training), I always try to design problems such that they provoke these questions:
1. What are the observations for this problem?
2. Is this solution correct?
3. Can we improve the solution further? (for efficiency in time/memory, for generalizations, etc.)
Now that my role as a contestant for the IOI is done, and I'm wandering around Codeforces, I feel rather dull about this. I argue that for now, many of the Codeforces problems focus on judging whether you can come up with a solution for the problem or not. They are "insight"-based problems. On the other hand, when I train (myself and others) fo...
?". Without these questions, I'd be bored by the education of algorithms.
Without these,research in
134.
very interesting research challenge hello codeforces
i want to suggest a research
let's call the **depth** of an english wikipedia page the smallest amount of clicks on links (in the text) to reach [this page](https://en.wikipedia.org/wiki/Furry_convention).
what is (approximately) the mathematical expectation of this value (the page is chosen randomly equiprobably)?
I'm waiting for your approaches (with description)!!!
**upd:** sorry didn't know such services exist, thought it'd be interesting to use some heuristics to estimate needed values. the thread can be closed now thanks for watching subscribe on youtube and o***f***
very interesting research challenge, i want to suggest a research
135.
How to expand the class of problems in CP without losing objectivity + simplifying organization **Who am I?** I took up ACM ICPC in 2006 as a student, went to the semi-finals 5 times, trained the teams of a provincial university, held several camps for schoolchildren from the zero level and above, and participated in the organization of regional competitions many times (ContestSfedu aka Championship of the South of the Russia aka GP of Azov Sea — Opencup). In recent years, I have been pursuing a career, so I do not actively participate in the sports program, but from time to time I continue to help in holding competitions in Taganrog.
**Why am I speaking out?** More and more often I find myself thinking that competition programming does not keep up with the rapidly changing world and it becomes more difficult to find arguments for students to do it. It's probably easier with schoolchildren, but it's only a matter of time. Do those who organize ICPC, school Olympiads, etc. understand this problem? — I don't know, because I'm not actively involved in the activities o...
be implemented on some platform unknown to me (I did not conduct research).
And suddenly not?
136.
Announcement: 1st Hello India x Russia Programming Bootcamp 
Hello, Codeforces!
We are pleased to announce the [**1st Hello India x Russia Programming Bootcamp**](http://in.harbour.space/icpc/acm-icpc-hello-india-bootcamp-spring-2018/?utm_source=Codeforces), with [Amrita School of Engineering](https://www.amrita.edu/campus/amritapuri), [Moscow Institute of Physics and Technology](https://mipt.ru/en/) in collaboration with [Moscow Workshops ACM ICPC](https://it-edu.mipt.ru/en/about_workshops), and of course Codeforces!
The boot camps will be held **from March 22nd to the 30th** in both India and Russia.
We would like to bring your attention to the **new Bootcamp Features:** Hello India x Russia Programming Bootcamp and Moscow Workshops ACM-ICPC will be running both boot camps side by side, every day each camp will be competing in parallel, 7,500 kilometers from each other.
In India and Russia, the Coordinators of the Programming Committee will be both **Gleb**...
**Amrita School of Engineering** — The campus has well established research
centres carrying, research.
137.
Dasha Code Championship <img src="/predownloaded/35/22/3522ae409c65c0dd8ea0d52d8e33decea25a2d19.png" style="float:right; margin: 0 1.5em 1.5em 1.5em;"/>
Hi Codeforces!
We are pleased to announce the start of registration for Dasha Code Championship! We are <a href="http://dasha.ai/">Dasha.AI</a> — a conversational AI startup with the huge ambition to use voice AI to pass the Full Turing Test. In a very short time, we managed to assemble a strong team of top specialists — among us there are 4 winners of international mathematics competitions, 16 ICPC participants, and several PhDs and Doctors of Science. Scientific research in the field of AI is led by [Alexander Dyakonov](https://www.kaggle.com/dyakonov) — Doctor of Physical and Mathematical Sciences, Professor of Moscow State University, Professor Emeritus of the Russian Academy of Sciences, former Kaggle #1.
Recently we’ve been featured on <a href="https://techcrunch.com/2019/08/01/dasha-ai-is-calling-so-you-dont-have-to/">TechCr...
participants, and several PhDs and Doctors of Science. Scientific research in
the field of AI is
138.
Huawei Honorcup Marathon 2 <img src="https://assets.codeforces.com/images/honorcup-marathon-logo.png" style="float: right; margin: 0 1em 1em 1em;"/>
Dear Friends!
If you dream of realizing your ideas in new technologies and products used by a third part of the world's population — join Honorcup Marathon. <b>It will be an unrated round for individual participation, as well as for teams of up to three people.</b>
<p style="margin: 2em;">
<center>
<a style="background-color: #3B5998; border: 2px solid #1A237E; padding: 5px 10px; color: white; font-weight: bold; text-decoration: none;" href="/contests/1235">Take part in the round →</a>
</center>
</p>
You will develop a quite challenging task without exact solution. Your solution with show up your programming skills, research and data analysis abilities.
**At stake**: we have Huawei devices for the top 3 winners, as well as 10,000 USD for top 1.
And, of course, TOP 80 participants will get a hoodie with Huawei Codecraft logo! During...
programming skills, research and data analysis abilities., without exact solution. Your solution with show up your programming skills,
research and data analysis
Announcement of Huawei Honorcup Marathon 2
139.
What I learned from Round 619 Div2 Time: 5:45pm IST
- Solved A
- Couldn't solve B
- Couldn't think of C
-- Up-solve :
- Read the question wrong for A and started swapping on all elements, should read carefully and remember A is the easiest so the probability of there being a catch is less.
- Started on right track of taking elements on the edge of -1 valleys. Should've added them in a vector more efficiently, instead I made complex vectors which was confusing. Then I did not think of a mathematical proof instead I made a intuitive guess which was wrong. Should try to get a mathematical proof for every question!
- Couldn't even think of going the opposite route of finding subsets of zeros. This mindset of solving something else to get something else always comes with Subset questions, I got one such previously too. Keep this in mind.
What I Learnt
- How to get max_element and min_element directly from arrays. ( cout<< *max_element( arr.begin() , arr.end()) )
- I wonder what is the complexity? O(N)? ...
() , arr.end()) ) - I wonder what is the complexity? O(N)? research ("YES") -
Find mathematical proofs, )? research ("YES") - Find mathematical proofs and don't get scared - Using
pop_back() function
140.
Algorithms in Academia Hey guys,
I know that many of the people here are young and want to know how does the algorithmic courses in universities work, how does research in the algorithmic field work, etc. I have started to upload some videos about it.
This semester, I am the teacher assistant of CMSC 351 (Algorithms) in University of Maryland. I want to cover all the topics and assignments in this class and solve them for you. In future, maybe I will also talk more about research in the algorithmic field (which means not solving a problem that an author has designed, but solving a problem that no one has ever solved it before)
Some of these topics are related to competitive programming as well (like induction, sorts, etc.), some are not (like Karatsuba algorithms that I've never saw someone using it in a contest). I uploaded these videos in a separated channel because I didn't want to pollute the channel about competitive programming.
So, if you are interested in such things, and want to know wh...
algorithmic courses in universities work, how does research in the algorithmic
field work, etc. I have started, universities work, how does research in the algorithmic field work, etc. I
have started to upload, will also talk more about research in the algorithmic field (which means not
solving a problem that
141.
help with research paper on LCS I was reading about algorithms to find LCS in O(nlogn) and i came through this research paper — [link](http://dl.acm.org/citation.cfm?id=359603)
It claims to find LCS in O((n+r)logn) where r are the number of matching pairs.
But I can't understand how the final algorithm is O(n+rlogn) , I guess the algorithm is O(n*r*logn) ,please clear my doubt I can't understand?
here's my code —
~~~~~
#include "bits/stdc++.h"
using namespace std;
char a[50001];
char b[50001];
int thresh[50001];
int freq[27];
int freq1[27][50001];
int main()
{
scanf("%s",a+1);
scanf("%s",b+1);
int c = 0 ;
for(int i = strlen(b+1); i >= 1; i--)
{
freq1[b[i]-'a'][freq[b[i]-'a']] = i;
freq[b[i]-'a']++;
}
fill(thresh,thresh+max(strlen(a+1)+1,strlen(b+1)+1),10000000);
thresh[0] = 0;
int N = max(strlen(a+1)+1,strlen(b+1)+1);
for(int i = 1; i <= strlen(a+1); i++)
{
for(int j = 0; j < freq[a[i] - 'a']; j++)
{
int k = lower_bound(thresh,t...
help with research paper on LCS, I was reading about algorithms to find LCS in O(nlogn) and i came through this
research paper
142.
Say anything you want about staying up late. Now, it's 5:38 in China and I, who is chinese, who is therefore in China, still awake.
Back to 3 years ago, I, who is in my senior high, even felt guilty for sleeping after 00:00.
Back to 1 years ago, I could still go to sleep at maybe 1:00~2:00.
Back to 3 months ago, it's before 3:00.
Back to 1 months ago, before 4:00.
The day before yesterday, I stay up all ningt to review for final exam.
And, on yesterday, to my surprise, I'm not even sleepy at night and I eventually go to sleep at 6:00.
Today, it's nearly 6:00 again. The sun dazzling outside seems to remind me, saying "bro, it's not proper time for sleeping" to me.
Anyway, not stopping myself from 3:00, not stopping myself from 4:00, I have to stop myself from at least 6:00.
It's said by some research that people who is staying up late tend to be irrational and maybe that's why I wrote this weird blog post.
Here's mine. Say anything you want about staying up late.
stopping myself from 4:00, I have to stop myself from at least 6:00. It's said
by someresearch that, It's said by some research that people who is staying up late tend to be
irrational and maybe
143.
Interactive sorting problem in atcoder I am trying to solve an interactive problem from atcoder's practice contest. The abridged problem statement is as follows:
~~~~~
Given the value of N where N ranges from [1,26] and Q where Q is the maximum number of queries that one can make, sort a list of distinct uppercase alphabets in ascending order. N indicates that there are N characters starting from 'A'. Hence, N = 5 means that our final list must contain 'A', 'B', 'C', 'D' and 'E'.
A single query is defined as printing out a string "? x y" where x and y represent the characters we want to check the relation between (e.g. "? A B"). The problem restricts the number of such queries to Q. Hence, we must determine the final order of the characters using at most Q queries.
For each query, we get a binary answer '<' or '>' from stdin. '<' indicates that x comes before y in the final list. '>' means otherwise.
~~~~~
Problem link: [here](http://practice.contest.atcoder.jp/tasks/practice_2)
(Do note that atcoder accoun...
that fulfils the constraints N=5, Q=7. After some research, I found that merge
sort's worst case, After some research, I found that merge sort's worst case number of comparisons
is n * ceil(logn
144.
Applying for PhD in CS: Is it possible for competitive programmers with no CS-related degrees? Hello,
I am majoring in theoretical ecology at the University of Tokyo. I am scheduled to graduate from the current MSc program in March 2020, and I am planning to get in a Ph.D. program (outside Japan, due to financial and other problems). My interests are mathematical/computational biology/ecology, combinatorics, graph theory, exponential algorithms, etc.
Currently, my biggest concern is that I have no CS degrees, or even something related to CS. I graduated from the University of Tokyo in ecology BSc. However, I have achievements and contributions in competitive programming area more than average (How 'more than average'? This is my list [Link](https://tozangezan.github.io/)).
Is it possible for non-CS students with competition achievements like me to get in CS PhD program to research algorithms? How are the chances? Does it depend on schools or region? I have no one to ask about it because almost all the redcoders are CS or mathematics major, and especially in Japan, very ...
to research algorithms? How are the chances? Does it depend on schools or
region? I have no one to, research algorithms? How are the chances? Does it depend on schools or region?
I have no one to ask
145.
Help us collect solutions from private online judges Hi,
Myself together with a small team of researchers are trying to teach machines solve competitive programming problems.
For that we need a large dataset of problems and solutions.
We have already crawled practically all websites that have public solutions, and are now trying to crawl solutions that are not public.
If you were solving problems from Timus, UVa or any other platform with private submissions, and are open to giving us access to your account to crawl the solutions, **please send your credentials** to me via a personal message. It will help us a lot with our research. The language in which you were solving problems doesn't matter.
We won't publish your code anywhere, and won't use the credentials in any way except for crawling the solutions.
Besides that a reminder that we have a labeling platform where we are trying to rewrite competitive programming problem statements in a short concise way. We pay for doing it, and many people who are presently helpi...
** to me via a personal message. It will help us a lot with our research. The
language in which you, , **please send your credentials** to me via a personal message. It will help
us a lot with ourresearch
146.
Open Problems in Algorithms Research for Ph.D. at Indiana University Hi all,
This is a follow-up on my previous blog post about Ph.D. positions in Algorithms and Machine Learning at Indiana University, USA (http://codeforces.com/blog/entry/45559 ). For the details about the application process see the original post and this link: http://grigory.us/phd-call.html (deadline for full applications is Dec 01, 2016).
Since that post generated some interest I have compiled a list of possible open problems in algorithms research to consider during a Ph.D.: https://www.dropbox.com/s/4mf2b6f9fa9rx91/open-new.pdf?dl=0 It is also intended to give one a sense of how modern research in algorithms looks like. The list includes a diverse set of problems covering massively parallel computation, clustering, various forms of graph sparsification, algorithmic questions in testing analytic properties of high-dimensional functions used in machine learning and topics in communication complexity.
Please, note that most of these problems are quite hard and have been stu...
Open Problems in Algorithms Research for Ph.D. at Indiana University, algorithms research to consider during a Ph.D.:
https://www.dropbox.com/s/4mf2b6f9fa9rx91/open-new.pdf?dl=0, compiled a list of possible open problems in algorithms research to consider
during a Ph.D.: https
147.
Teach algorithms to high schoolers in Ethiopia or Jamaica? Hi all,
I'm now an old man, but I grew up in the programming contest community back in my youth ~15 years ago (back when [TopCoder](https://www.topcoder.com/members/Minilek) and the UVA online judge were more popular), and I don't think I'd have ended up with my current job as a computer science professor doing algorithms research without that experience.
I want to share that experience with others, so in the last ~10 years I started algorithms summer camps [AddisCoder](https://addiscoder.com/) and [JamCoders](https://jamcoders.org.jm/) to teach algorithms to high school kids in Ethiopia and Jamaica, respectively (see what topics we teach [here](https://addiscoder.com/syllabus/2019)). These are each 4 week programs, 40 hours per week, with teaching assistants showing up a week early to help prep.
If you would like to volunteer as a teaching assistant for either program, please apply ([AddisCoder application link](https://addiscoder.com/#apply), [JamCoders application link](htt...
doing algorithms research without that experience.
148.
The Beginner’s Guide to Kaggle How do I even start?
Will I be up against teams of experienced Ph.d researchers?
Is it worth competing if I don't have a realistic chance of winning?
Is this what data science is all about? (If I don't do well on Kaggle, do I have future in data science?)
How can I improve my rank in the future?
Well, if you've ever had any of those questions, you're in the right place.
In this guide, we'll break down everything you need to know about getting started, improving your skills, and enjoying your time on Kaggle.
Kaggle competitions
By nature, competitions (with prize pools) must meet several criteria.
Problems must be difficult. Competitions shouldn't be solvable in a single afternoon. To get the best return on investment, host companies will submit their biggest, hairiest problems.
Solutions must be new. To win the latest competitions, you'll usually need to perform extended research, customize algorithms, train advanced models, etc.
Performance must be relative. Competiti...
have the largest prize pools. Research — These are research-oriented and have
little to no, must be new. To win the latest competitions, you'll usually need to perform
extendedresearch, research, customize algorithms, train advanced models, etc. Performance must be
relative
149.
Invitation to join the UP ACM Algolympics 2024 Final Round Mirror at the Codeforces Gym Greetings of peace, Codeforces!
I'd like to invite you to the mirror of the UP ACM Algolympics 2024 Final Round. Algolympics is an annual contest organized by the Association for Computing Machinery, University of the Philippines Diliman Chapter. It is open to teams consisting of undergraduate college students from the Philippines. This year's contest was held on April 4, 2024, and was the first on-site Algolympics since the pandemic. It was a lot of fun! And I hope the CF community has just as much fun with these problems.
Contest details:
- There are 13 problems over 5 hours.
- Every problem is worth 1 point.
- Scoring is binary. There are no partial points.
- The penalties are ICPC-style.
- [Click here to go to the gym contest](https://codeforces.com/gym/105093)
The problems range from easy to challenging. The problem setters are myself---[user:Shisuko,2024-04-09]---[user:PPTGamer,2024-04-09], [user:alltootechnical,2024-04-09], and Josh Quinto ([user:1NCID3R,2024-04...
-04-09]) and some of his colleagues in Samsung Research. Thanks to
MikeMirzayanov for Codeforces and, :1NCID3R,2024-04-09]) and some of his colleagues in Samsung Research. Thanks to
MikeMirzayanov for
150.
'/' or '//' division — python3 Hello Codeforces community!!
This is my first post on codeforces. I am not a regular writer who would post ideas or things because the things i used to find out seemed trivial(This post may seem trivial to many of you :D) to me earlier. But not until 2 days ago when i encountered a kind of mistake in my code. I hope this post help other python3 users or those trying to make a shift to python3.
**What happened:** I got wrong answer for Problem A [979A](http://codeforces.com/contest/979/problem/A) . As a normal user i checked, rechecked my logic for it. Read editorial also, it matched my logic too. Looked into [test case](http://codeforces.com/contest/979/submission/38222153) that made it fail.
**My Code**
~~~~~
n = int(input())
if n != 0:
if (n+1)%2:
print(n+1)
else:
print(int((n+1)/2))
else:
print(0)
~~~~~
Seems the logic is correct so, why it is failing for test case 11. Researched a lot on topics i didn't understood before. Thanks to ~PikMike,2018-...
151.
Master's thesis about competitive programming? Hi!
Next year I'll start working on my Master's thesis (in computer science), and we have to choose the subjects now. I'm not very enthusiastic about the subjects that are suggested by default but we are allowed to suggest our own topics if we want. So I got an idea: what if I could work on a topic related to competitive programming?
I have good relationships with some of the teachers so I should be able to convince one of them to accept it if it's an interesting subject. But it's not that easy to find a good subject on that theme.
An example I thought of would be to study the current state of the art in a subfield like geometry: which kinds of problems appear in which competitions, which algorithms are considered common knowledge, which kinds of implementations are used, how precision issues are dealt with, etc. I would try to summarize that and to figure out by reviewing the research litterature which new algorithms or techniques might appear in the future, thanks to which i...
to summarize that and to figure out by reviewing the research litterature
which new algorithms or, research litterature which new algorithms or techniques might appear in the
future, thanks to which
152.
Interview with a member of the Vaticle team — Krishnan _Hello, everyone!_
_We look forward to our upcoming competition — [contest:1787], which will take place on [contest_time:1787]. In the meantime, you can learn a little more about us._
_We’re from [Vaticle](https://vaticle.com), and we’re the creators of [TypeDB](https://github.com/vaticle/typedb) & [TypeQL](https://github.com/vaticle/typeql). All members of our team are unique and talented, and today we want to introduce you to one of them._
<center>
<img alt="Vaticle" src="https://codeforces.com/predownloaded/03/46/03464753d3d754055dc6d379d123120c44908937.jpeg" style="float:center;height: 400px; margin: 10px; max-width:70%;"/>
</center>
**<font color="#170b53">How would you introduce yourself?</font>**
I'm Krishnan, I grew up in India and spent a little too much time on the internet and fiddling with my (underpowered) PC. After completing my Bachelor's degree, I spent a year as a software engineer working on a huge data lake, the next as a research fellow tr...
working on a huge data lake, the next as a research fellow trying to permute
thread executions to
153.
Jobs similar to CP by work style, not by technical knowledge Alt/Throwaway account here for privacy reasons. My main account is red.
**TL;DR**: I am not cut out to be a researcher. Asking for help.
It has always been a no-brainer for me that I would end up in a research job. However, after I made it last fall, I realized how different it is from CP and anything I had previously experienced at the university. The research requires analyzing and generating ideas for a particular problem for months. However, I would always encounter an obstacle in the first hour, which made me unable to move forward.
I believe the common knowledge of the research being the default career path must change. My understanding is that this view is reinforced by survivorship bias, where the CP community stops hearing about research dropouts, making the successful not realize how high the dropout rate is and universally label the doubters as having imposter syndrome (which is 100% real but overused).
I would like to raise points to discuss:
1. Are there job...
up in a research job. However, after I made it last fall, I realized how
different it is from CP and, I believe the common knowledge of the research being the default career path
must change. My, It has always been a no-brainer for me that I would end up in a research job.
However, after I made
154.
JetBrains Knowledge Day 2020: Train Hard, Code Easy [<img src="/predownloaded/a7/0d/a70dcbadf03a67c9fe230e11647c30a1b79fbaa5.png" align="right" style="height: 200px; margin: 10px 30px 20px;" alt="text"/>](https://challenge.icpc.global/)
Dear friends!
We are thrilled to invite you to join us in this unique educational event to mark the beginning of ICPC competitive season and the academic year. Join us in **JetBrains Knowledge Day** on November 6!
<center style="margin: 2.5em;"> <a href="https://pages.jetbrains.com/knowledge-day-2020/icpc" style="text-decoration: none;font-size: 18.0px;background-color: rgb(157, 1, 45);color: white;font-weight: bold;padding: 0.5em 1.0em;">Join now</a>
<a href="https://youtu.be/IVC5FjmKriI" style="text-decoration: none;font-size: 18.0px;background-color: rgb(157, 1, 45);color: white;font-weight: bold;padding: 0.5em 1.0em;">Live broadcast</a>
</center>
You will learn firsthand tips from the JetBrains team about performance tuning in CLion and IntelliJ IDEA, the advantages of Kotlin for al...
Elizarov, Team Lead in Kotlin Language Research) - **11:30 am – 12:00 pm UTC**
— Train Hard, Code Easy, Research) - **11:30 am – 12:00 pm UTC** — Train Hard, Code Easy: Best Practices
for Competitive
155.
Collection of useful resources over the codeforces Hey Codeforces community..Here is my list of resources after a research over codeforces
1.All good resources — https://codeforces.com/blog/entry/57282
2.Problems on DP — https://codeforces.com/blog/entry/67679
3.All problem topics — https://codeforces.com/blog/entry/55274
4.Excellent Dp — https://codeforces.com/blog/entry/43256
5.Learning website — https://www.vplanetcoding.com/course2
6.DP — all templates — https://codeforces.com/blog/entry/73446
7.SOS DP — https://codeforces.com/blog/entry/45223
8.Generating Functions — https://codeforces.com/blog/entry/77468
9.Cpp Tricks — https://codeforces.com/blog/entry/74684
10.Slope Trick — https://codeforces.com/blog/entry/77298
11.Convex Hull — https://codeforces.com/blog/entry/63823
12.Array Algorithms — https://codeforces.com/blog/entry/72253
13.XOR techniques — https://codeforces.com/blog/entry/68953
14.Graph colori...
Hey Codeforces community..Here is my list of resources after a research over
codeforces
156.
Transition from CP to TCS (Theoretical Computer Science) Research Hello, Codeforces Community!
Since my middle school days, I've been deeply involved in Olympiad Informatics, which sparked my passion for algorithms and data structures. Now, as a first-year computer science undergraduate, my ambition is to pursue a career in theoretical computer science (TCS) research.
I would greatly appreciate any advice from those currently engaged in TCS or combinatorial optimization research.
Transition from CP to TCS (Theoretical Computer Science) Research, ambition is to pursue a career in theoretical computer science (TCS) research., optimization research., ) research. I would greatly appreciate any advice from those currently engaged
in TCS or
157.
2023-The 5th Turing Cup Tournament **Turing Cup Tournament**
The Turing Cup is an invitational competition that is organized by one of the most successful informatics competition teams in China, the XinYouDui and partner with X-Camp Academy.
**Registration time:** April 7th — May 13th 12:30 PM（BJT）/ May 12th 9:00 PM PDT/ May 13th 00:30 AM EDT
**Registration method:** Click XinYouDui contest system directly for registration. So [register here while you can](https://contest.xinyoudui.com/recommend)! (It is recommended to use Chrome, Firefox browser)
**Registration requirements:** There are no age, level, or identity restrictions.
**Discord Link**: [Join the discord for Q&As and discussions](https://discord.gg/6SkkJ3f55p)!
These awesome problems and editorials are written, prepared, and tested by the X-Camp and XinYouDui Team, **including 4 Chinese national team members,**
[user:orzdevinwang,2023-05-12], [user:Rebelz,2023-05-12], [user:hehezhou,2023-05-12], [user:djq_cpp,2023-05-12], [user:unputdo...
inherited from Mr. Xianyou Xu, and re-develop by our teaching research team in
the US. Our staff is mainly
158.
A Brief Inquiry into Online Connectivity This question striked my head: *"How can I solve dynamic $k$-connectivity efficiently?"*
And then I tried to answer it, but I realized that my question was open to a lot of different interpretations.
Two vertices are $k$-connected if there are $k$ edge-disjoint paths connecting two vertices. For $k = 1$, it is the usual definition of *connectivity*.
## Solve?
If I say, "I solved the graph connectivity problem", what can it possibly mean?
**First Interpretation ($s$-$t$ connectivity)**. I can respond to the following query efficiently: Given two vertices $s, t$, determine if there is a path between them. In the case of $k = 1$, graph search suffices.
What about higher $k$? You can find $k$ edge-disjoint path by reducing it into a flow problem. Each edge-disjoint path corresponds to a flow from $s$-$t$, so make all edges to capacity one, and find a flow of total capacity $k$ from $s$ to $t$. This algorithm takes $O(\min(k, m^{1/2}) (n + m))$ time.
**Second Interpre...
://www.cs.princeton.edu/research/techreps/TR-228-89 * Maintains $2$-connected
component
159.
Have you seen this data structure before? Introduction:
=============
Hello codeforces,
In this blog, we will explore a technique for efficiently handling insertions and deletions in arrays using partitioning and deques. I cannot be certain if this idea has been previously explored or not, but I have conducted extensive research and consulted with friends to determine if a similar concept exists. If you have come across this idea before, I kindly request that you share the relevant link and acknowledge the original author's novelty in developing it And if no similar idea exists, then it seems like I've stumbled upon my very own data structure creation LOL. I have developed a method that leverages partitioning and deques to optimize array operations. I invite you to read about this efficient data structure and welcome your feedback and insights.
### Understanding Partitioning and Deques:
Before delving into the technique, let's briefly understand the key concepts involved:
**1.1 Partitioning**
Partitioning invo...
previously explored or not, but I have conducted extensive research and
consulted with friends to
160.
About me! First of all, let me introduce myself, I am Assan and recently I have been working in ITmen as a Network Engineer.
The undergraduate curriculum in Computer Science and Engineering at institute of technology, , Ethiopia introduces me to a wide variety of engineering subjects. Various courses like Artificial Intelligence (Robotics), Programming Languages, Electronics I&II, Software Engineering, System Programming, Micro Processor, Interfacing & Assembly, Algorithm Analysis and Design, Digital Signal Processing, Network and System Security, Digital system, Algorithm analysis and design, Computer graphics and multimedia, Computer Simulation and Modeling provided me with a strong footing in the theoretical concept of Computer Science and Engineering.
While offering both depth and breadth across this field, these courses put into perspective the importance and relevance of Computer Science and Engineering and the application of its fundamentals to the problems faced by the real world....
extremely distinguished faculty members, and research facilities are the
factors which have motivated
161.
Codeforces: new computers for testing and testing compatibility mode Rah-rah!
We are moving forward to accelerate testing. In fact, when our rounds attract 3500+ registrations, it is hard to test all the submissions on nine computers "Core 2 Duo E6750, 2.66 Ghz, 3Gb".
Computer Science Department of Saratov State U has recently got 20 new computers i5-3470, 8Gb. After a little research it was found that if boost CPU to 3.5Ghz (of course, turning off all sorts of turbo boost and after many hours of stability check), the speed is approximately equal to twice the speed of the old testing machines. This is very convenient as it will in future only to divide all the time constraints in the problems by 2.
We have moved to testing on new computers and we do it in **compatibility mode**. This means that all the time constraints before the start of the program are divided into 2, the program is executed, and at the end a running time is multiplied by 2. In fact, if you do not use the cut-off by time or some other unsavory stunts, you will not detect any ...
. After a little research it was found that if boost CPU to 3.5Ghz (of course,
turning off all sorts
162.
Which AI feat would be most impressive? There has been recent buzz and discussion surrounding the potential of AI to be competitive in math and programming contests, prompted by recent initiatives such as the [AIMO prize](https://aimoprize.com/), which promises to award a $5 million dollar prize to an AI who is able to earn a gold medal at the IMO, and Google's [AlphaCode2](https://codeforces.com/blog/entry/123035), which has been claimed to be able to compete in Codeforces contests near the level of a CM.
Which of the following tasks do you think would be the most difficult and most impressive for an AI to accomplish:
- Winning a gold medal at IMO
- Winning a gold medal at IOI
- Winning a Div. 1+2 Codeforces contest
- Writing/preparing a well-balanced, well-received Div. 1+2 Codeforces contest
(You can vote for multiple options.)
How soon, if ever, do you predict these milestones to be reached?
If an AI can beat the best humans at a Codeforces contest, what does this m...
research? Please discuss!
163.
Yandex.Algorithm ML track started [Yandex.Algorithm](https://contest.yandex.com/algorithm2018/) ML track started! Hope you will participate it)
The task has been prepared by the Yandex.Alice team and personally Slava Alipov
[user:eik0u,2018-04-01].
Building an open-domain conversational assistant that is clever and fun is
one the most exciting applications and research frontiers of
artificial intelligence nowadays.
The core and very challenging task of such an assistant is providing coherent
and entertaining replies to the users at all steps of their conversation with
the assistant.
Participating in our competition you can to feel closer to the creation
of the conversational assistant able to talk with millions of users
like Alice does every day.
Submissions should be sent until 10:00 23rd April (MSK).
Top 128 participants will receive cool t-shirts.
The best three will receive cash prizes.
One can share approaches and discuss the contest with other participants
in \#proj_algo_alic...
applications and research frontiers of artificial intelligence nowadays. The
core and very, one the most exciting applications and research frontiers of artificial
intelligence nowadays
164.
CF's secret that mike doesn't want you to know about^^ ok so i've been grinding for years now until i discovered this secret.
it's honestly so shocking how this glitch isn't patched yet. I was thinking that this website is huge, surely someone should've discovered it, but to my surprise it still works. before you guys go judging my g [user:MikeMirzayanov,2022-02-04], it's not his fault, as it took me years.. no.. decades of searching to find this.
so before i tell y'all this glitch i wanna show you my graph before knowing that it existed.
you might think that it's suspiciously similar to [user:sus,2022-02-04]'s graph, but i assure you that it's just a coincidence.
now let me get into the real stuff. one sunny morning i was having a thought that there has to be a way, or a hack, some might say a glitch to gain a lot of rating in such a limited amount of time, and my thought was correct! there is a way, and it has something to do with y...
sabotaged his rating. i was devastated and confused. did all my research go to
waste?? what went wrong
165.
Algorithms Problem for Research Project Hi all,
For a research project I am conducting, I have come across an algorithms problem. I would like a solution which runs in at most 1 hour or so. Can someone give me an idea? Thank you!
Find all permutations a such that a has 28 elements and:
a has 8 cycles of length 3 and 4 fixed points
b is ({1,2,3...,7}, {8,9,10...,14}, {15,16,17...,21}, {22,23,24,...,28}) cycle structure
a * b has 14 cycles of length 2.
Algorithms Problem for Research Project, For a research project I am conducting, I have come across an algorithms
problem. I would like a, Hi all, For a research project I am conducting, I have come across an
algorithms problem. I
166.
Dominator Tree [Tutorial] Hi!
I have tried to explain the concept and algorithm for building the Dominator Tree of a directed graph with respect to a source vertex in this article :
[https://tanujkhattar.wordpress.com/2016/01/11/dominator-tree-of-a-directed-graph/](https://tanujkhattar.wordpress.com/2016/01/11/dominator-tree-of-a-directed-graph/)
The algorithm was published by Robert Tarjan in his original research paper [here](https://www.cs.princeton.edu/courses/archive/fall03/cs528/handouts/a%20fast%20algorithm%20for%20finding.pdf). There are not much resources on the topic, except the original research paper , on the internet. The topic is fairly advanced and involves a lot of theory.
Kindly read and give your feedbacks !
Happy Coding :)
**Edit :** A link to the pdf version of the article has been added in the Blog Post. :)
original research paper
[here](https://www.cs.princeton.edu/courses/archive/fall03/cs528/handouts/a, The algorithm was published by Robert Tarjan in his original research paper
[here](https
167.
A job for the red one Hi guys!
I'm currently unemployed, looking for a job and would like to make some survey here, basically the topic would be "the interesting job". To give you a quick introduction: I was working as a .Net developer for around 7 years in different but more or less similar outsourcing companies, I've started participating in competitive programming 1.5 years ago and eventually this ruined my career in regular outsourcing cause the tasks there most of the time are more boring and less brain-teasing than what you have in CP.
To be clear, what I want here is to have as much opinions as possible, I would appreciate any ideas, consider this topic to be a brainstorming platform. I just want to broaden my understanding of what is there outside of the companies where I was working before. I'm interested to hear about your companies (I won't blame you if you decide to advertise your company in this blog post), or maybe you won't give out the company name but will share what do you do there,...
), maybe you're working in CS-research centres, maybe in some educational
centre, maybe you're, -related (but still supposed to be interesting for a programmer), maybe you're
working in CS-research
168.
Thought Experiment About Improving ICPC Team For context, please refer to [this thread] (https://codeforces.com/blog/entry/64791). TLDR: over the past four years, Georgia Tech has always placed second in our ICPC regional contest, and did not advance to the ICPC World Finals due to the region repeatedly being allocated only one slot.
I would like to try a thought experiment: are there CF users with ratings 2400 or higher, are ICPC eligible for WF20 (based on extrapolations of the [criteria for WF19](https://icpc.baylor.edu/download/regionals/rules/EligibilityDecisionTree-2018.pdf)), and would be interested in spending a year at Georgia Tech from mid-August 2019 to May 2020? The tentative plan for funding is at the Masters student rate (full tuition coverage, plus a stipend of about 1500 USD / month), with other responsibilities being TAing for algorithms courses and conducting research.
If you are interested, please email me at [email protected] with your CF id, and ideally, a short CV. Please also note that while I'm ext...
being TAing for algorithms courses and conducting research. If you are
interested, please email me, responsibilities being TAing for algorithms courses and conducting research.
169.
Hosting contests: x86_64 or ARM64? TLDR: will people get angry if the judging servers for a contest use ARM64?
I'm setting up the hosting infrastructure for the [Bay Area Programming Contest](https://bapc.gunncpc.com) using DOMjudge, and as part of this setup I need to choose what machines the judgehosts will run on. I've decided to use AWS EC2 for hosting since I've already tested setting up DOMjudge as a dry run on there.
Of the machine families that EC2 provides, I've chosen to go with the burstable (T) instances, run in unlimited mode. (Also, if anyone has experience with using these for programming contests, I'd love to hear how it went for you. I read through some [AWS docs](https://aws.amazon.com/ec2/instance-types/) and it seems that the compute performance should be stable if run in unlimited mode, but I haven't done any hands-on testing yet.) I'm currently picking between the T3 and T4g instances. T3 runs x86_64 and T4g runs ARM64.
I would like to use T4g because it's cheaper, but I'm concerned that s...
avx2 pragma) only work on x86_64 and that people will be angry about that. I
tried doing someresearch, that. I tried doing some research into what architectures are commonly used in
CP judges and I could
170.
The Relationship between CF Rating and WPM Hello Codeforces! Recently, there was a blog about [the relationship between IQ and Codeforces rating](https://codeforces.com/blog/entry/90996). And this blog inspired me to do a similar thing for typing speed.
Unfortunately, I don't have any fancy research paper that proves the relationship between WPM and CF rating. To have an idea about it, I created this blog. When I reach about 50 responses, I'll post what I come up with.
To take part in this, you need to take a 30 second English word typing test from [MonkeyType](https://monkeytype.com/).
Further instructions are included in the form. As a note, I know that taking the test with punctuation and longer time may differ in WPM by a lot. But, to not bore you and take your time, I concluded that selecting the test only as 30 seconds and only with words would be better.
Thank you for participating. [Take me to the form.](https://forms.gle/ZB9okemHZhCcWBDD6)
Edit: Form is closed.
Shout out to [user:dnaux,2021-06-01] and [us...
typing speed. Unfortunately, I don't have any fancy research paper that proves
the relationship, Unfortunately, I don't have any fancy research paper that proves the
relationship between WPM and
171.
bitset Find_first and Find_next Hi !
Today while solving [problem:356D] I needed a function for `bitset` in order see what is the first set bit.I asked [user:M.Mahdi,2016-03-10] and he told me about `bs._Find_first()`. for example:
~~~~~
bitset<17>BS;
BS[1] = BS[7] = 1;
cout<<BS._Find_first()<<endl; // prints 1
~~~~~
After more research , we found `bs._Find_next(idx)`. This function returns first set bit after index idx.for example:
~~~~~
bitset<17>BS;
BS[1] = BS[7] = 1;
cout<<BS._Find_next(1)<<','<<BS._Find_next(3)<<endl; // prints 7,7
~~~~~
So this code will print all of the set bits of BS:
~~~~~
for(int i=BS._Find_first();i< BS.size();i = BS._Find_next(i))
cout<<i<<endl;
~~~~~
Note that there isn't any set bit after `idx`, `BS._Find_next(idx)` will return `BS.size()`; same as calling `BS._Find_first()` when bitset is clear;
**UPD** One question, bitset is 32 or 64 times faster than bool array?
~~~~~ After more research , we found `bs._Find_next(idx)`. This function
returns first set bit after, After more research , we found `bs._Find_next(idx)`. This function returns
first set bit after
172.
Teams going to ACM ICPC World Final 2017 Europe
==================
| Count | Country | Region | University | Member 1 | Member 2 | Member 3 |
| ----- | ------- | ------ | ---------- | -------- | --------- | -------- |
| 1 | Russia | NEERC | St. Petersburg State University | [user:aid,2017-05-22] | [user:ershov.stanislav,2017-05-22] | [user:-XraY-,2017-05-22] |
| 2 | Russia | NEERC | St. Petersburg ITMO University | [user:izban,2017-05-22] | [user:enot110,2017-05-22] | [user:Belonogov,2017-05-22] |
| 3 | Russia | NEERC | Moscow Institute of Physics & Technology | [user:zemen,2017-05-22] | [user:ifsmirnov,2017-05-22] | [user:Arterm,2017-05-22] |
| 4 | Russia | NEERC | Ural Federal University |[user:Tinsane,2017-05-22] | [user:kb.,2017-05-22] | [user:KungA,2017-05-22] |
| 5 | Russia| NEERC | Perm State University | [user:I_love_Tanya_Romanova,2017-05-22] | [user:mmaxio,2017-05-22] | [user:KuchumovIlya,2017-05-22] |
| 6 | Belarus| NEERC | Belarusian State University of Informatics and Radioelectronics |[user:netman,2...
| NEERC | Samara National Research University | [user:pitfall,2017-05-22] |
[user:Slamur,2017-05-22
173.
Codeforces WatchR: Contests++ Have you ever felt like there are **not enough contests** on Codeforces? Nothing to do this weekend? Well, then go to **App Store** and download [Codeforces WatchR](https://apps.apple.com/us/app/codeforces-watchr-contests/id1495591299).
There you will find upcoming contests for **all major competitive programming platforms**:
- Codeforces
- TopCoder
- AtCoder
- CS Academy
- CodeChef
- HackerRank
- HackerEarth
- Kick Start
- LeetCode
This wouldn't be possible without **great open-source project** — [KONTESTS](https://www.kontests.net), which gave us super-easy access to compiled list of all those contests. **Big thanks to all of you guys: Ali H. Fadel, Ridah O. Labbar, Ibraheem Z. Tuffaha.** Give them some love by starring official [GitHub repo](https://github.com/AliOsm/kontests) ;)
This feature is currently available in [iOS app](https://apps.apple.com/us/app/codeforces-watchr-contes...
] and his efforts in research and development.
174.
Competitive Programmers' Dilemma Hello guys,
I decided to use a fake account for this post. I want to talk about a problem I am facing, which I guess might be common among many people in this community.
I am a junior year student in university and I am doing a summer internship at a reputed tech company. I find my job tremendously boring; Most of my day to day work is reading lots of documentation and implementing things. The hardest part of work is to make sure my code sits well within the existing framework.
I don't find this job exciting at all, but it pays really well. I have student loans and I pay them off by doing such internship every year. My past internships have been equally boring. My question to you is, what would you suggest to someone like me for the future?
To give some context, I am a mediocre competitive programmer. My actual CodeForces rating is around 1900-2000 and I haven't gone to ICPC World Finals or IOI. Even outside the competitive programming world, my problem-solving skills are ...
mathematics. I would like to do research (PhD) after university, but I don't
think I am smart enough., - Get high paying job as software developer. Accept the fact that it is boring.
- Tryresearch, research (PhD) after university, but I don't think I am smart enough. I can see
two possibilities for
175.
Teach Algorithms to high schoolers in Ethiopia? Hi all,
I personally "grew up" in the programming contest community, especially before Codeforces began when TopCoder and UVA were two of the biggest sites. I'm now a [computer science professor](http://people.seas.harvard.edu/~minilek/) with a research focus on algorithms, which I don't think would have been true if it weren't for sites like this one. After my own experiences in my youth, I decided in my free time to provide such an experience for some young folks.
I co-organize a free intensive 4-week summer program in Addis Ababa, Ethiopia introducing high schoolers to programming and algorithms (AddisCoder: addiscoder.com). Over 150 students have completed previous iterations of the program. The students are very good. Alumni have gone on to study at Harvard, MIT, Princeton, Columbia, Brown, and many other institutions in the U.S., Ethiopia, Germany, and U.A.E. They have also gone on to work both as interns and full-time software engineers at Facebook, Google, Microsoft, Orac...
://people.seas.harvard.edu/~minilek/) with a research focus on algorithms,
which I don't think would have, ](http://people.seas.harvard.edu/~minilek/) with a research focus on
algorithms, which I don't think
176.
Ph.D positions in Algorithms and AI at GMU (Washington, DC) 
Hi all,
We have Ph.D. positions in algorithms and artificial intelligence available at George Mason University (Washington, DC) for students interested in doing cutting-edge research and publishing in top computer science venues (AAAI, FOCS, ICML, NeurIPS, SODA, STOC, etc.). Over the years our group has maintained active collaborations with research groups at leading industrial organizations, including Amazon NYC, Facebook HQ, and Google (HQ and NYC). Onsite visits can be organized for selected candidates.
Ph.D. ($25-30K/year), details at: [http://grigory.us/phd-call-f24.html](http://grigory.us/phd-call-f24.html)
Deadline: December 01, 2023.
Our past and present interns and students include [user:Chameleon2460,2023-09-08], [user:dyukha,2023-09-08], [user:josdas,2023-09-08] (at this time, internships are not available). For more information on our group and alumni placements, you can check [http://grigory.us/#group-alumni...
University (Washington, DC) for students interested in doing cutting-edge
research and publishing in top, interested in doing cutting-edge research and publishing in top computer
science venues (AAAI, FOCS
177.
ACM-ICPC World Finals 2014: Before Opening Ceremony Oh yes! Only a few days left before the Championship finals! The teams have already gathered in Yekaterinburg, most of them have registered and are watching a game between Russia and Belgium.
I want to start from some history and remember that the tradition to publish travel notes about Saratov State University's trips to finals started back in 2005. The regular pattern is that almost every year when we made notes, our team won a medal. I won't try my luck, so here are some of the first impressions of this year.
[cut]
The Codeforces community knows this year's team very well, its members are:
* [user:Gerald,2014-06-23] — Gerald Agapov, a person who coordinates Codeforces problems. He has been the key person collaborating with problem authors for Codeforces rounds since 2012. Oh yes, if something goes wrong with problems, he is the one I beaker at, but the guy is great and we hardly ever hae any problems :-) Gerald isn't only into programming. He loves maths, magnifi...
Research Center of MSU and he tried studying in MSU. He appeared in SSU summer
personal training camps
178.
TCO22 Algorithm Competition Round 1A It's that time again and we are excited! The first Online Round of the [2022 Topcoder Open](https://tco22.topcoder.com/) Algorithm Competition has arrived and is open to all!
Details:
- Round 1A: [Saturday April 16, 2022 at 12:00 UTC -4](https://www.timeanddate.com/worldclock/fixedtime.html?msg=TCO22+Algorithm+Round+1A&iso=20220416T12&p1=98)
- Registration Closes: 11:55 UTC-4
- Code Phase Starts: 12:05 UTC-4
- Where to compete: [Arena or Applet](https://www.topcoder.com/community/arena)
- [Click here to what time it starts in your area](https://www.timeanddate.com/worldclock/fixedtime.html?msg=TCO22+Algorithm+Round+1A&iso=20220416T12&p1=98).
Up to 750 of the highest scorers from each Round 1 will advance to Round 2 of the Algorithm Competition.
If you're unable to make it or don't advance, there will be one more Round 1 — Round 1B on [Wednesday, April 27, 2022 at 07:00 UTC -4](https://www.timeanddate.com/worldclock/fixedtime.html?msg=TCO22+Algorithm+Round+...
PS: Please help our research friends with [this
survey](https://neu.co1.qualtrics.com/jfe/form
179.
Help needed in CSES Graph Problem-Mail Delivery. [Problem Link](https://cses.fi/problemset/task/1691).
I am facing Time Limit Exceed in this problem and I am not able to improve my code any further.
(The following code is in python, but I have even tried in same thing in C++ and got TLE for last test case.)
<spoiler summary="My Code">
~~~~~
import sys
input = sys.stdin.readline # for fast input...
# graph input. n->no of nodes, m->no of edges...
n,m = map(int, input().split())
# constructing bidirectional graph...
# I am using '0' based graph indexing...
graph = [[] for _ in range(n)]
for _ in range(m):
a,b = map(int, input().split())
graph[a-1].append(b-1)
graph[b-1].append(a-1)
g = 0 # g is an indicator variable, g->1 means "impossible".
# degree of each node should be even for Eulerian cycle in undirected graph...
for i in graph:
if len(i)%2:
g = 1
break
if g:
print("IMPOSSIBLE")
else:
# using stacked method to find Eulerian path to avoid recursion (method link given)...
stack = ...
some further research. Any kind of help is acceptable :)
180.
Ph.D positions at George Mason University (Washington, DC) 
Hi all,
We have Ph.D. positions in algorithms and machine learning available at George Mason University (Washington, DC) for students interested in doing cutting-edge research and publishing in top computer science venues (AAAI, FOCS, ICML, NeurIPS, SODA, STOC, etc.). Over the years our group has maintained active collaborations with research groups at leading industrial organizations, including Amazon NYC, Facebook HQ, and Google (HQ and NYC). Onsite visits can be organized for selected candidates.
Ph.D. ($25-30K/year), details at: [http://grigory.us/phd-call-f23.html](http://grigory.us/phd-call-f23.html)
Deadline: December 01, 2022.
Our past and present interns and students include [user:Chameleon2460,2022-09-07], [user:dyukha,2022-09-07], [user:josdas,2022-09-07] (at this time, internships are not available). For more information on our group and alumni placements, you can check [http://grigory.us/#group-alumni](http:...
(Washington, DC) for students interested in doing cutting-edge research and
publishing in top computer, interested in doing cutting-edge research and publishing in top computer
science venues (AAAI, FOCS, ICML
181.
So... what's after CP? Hey there,
Two and a half years ago, I started doing CP, and it's a very fun and meaningful experience that I will cherish. But at some point, I just started growing tired of it (perhaps because I wasn't improving that much anymore), and I also realized that the computer science world is way larger than just CP.
**So... what's after CP? What did you do after you "retired" from CP? Which area of CS did you explore?**
I'm genuinely a bit lost and don't know what to do. For the past 6 months or so, I tried exploring stuff like Machine Learning, Computer Theory, and topics closer to theoretical CS, but felt like I wasn't making much progress without a teacher or a "partner" that could help me when I'm stuck (on that note, should I cold email university professors for research/learning opportunities?) I also don't know any stuff related to "developing" — I tried writing a chess engine in c++ and was also stuck, and I don't really _know_ any of the programming languages that ...
help me when I'm stuck (on that note, should I cold email university
professors forresearch, that note, should I cold email university professors for research/learning
opportunities?) I also
182.
What is the fastest known solution for the Counting Necklaces problem? Hello codefoces users.
A while ago, I solved CSES problem 2209 ([https://cses.fi/problemset/task/2209](https://cses.fi/problemset/task/2209)) related to combinatorics involving necklaces (https://en.wikipedia.org/wiki/Necklace_(combinatorics)) with a time complexity of O(sqrt(n) + divs(n) * (divs(n) + log(n))). I believe this complexity can be further reduced to O(sqrt(n) + divs(n) * (2^(nOfPrimes(n)) * log(divs(n)) + log(n))).
Upon reading the editorial, I discovered that the official solution utilizes Burnside's Lemma and has a time complexity of O(nlogn). I was unsure if my solution was previously known or not.
After conducting some research, I was unable to find a similar solution to mine. Consequently, I considered using this problem with higher constraints in a future contest. However, I am uncertain whether this is a wise decision. Therefore, I have two questions:
1. Is there a known solution with a better time complexity for this problem than my approach?
2. Would ...
was previously known or not. After conducting some research, I was unable to
find a similar, After conducting some research, I was unable to find a similar solution to
mine. Consequently, I
183.
How to find first digit of product of array elements ? Recently my friend was asked this problem in his coding test
- You are given an array of positive integers and Q queries.
Each query if of three types
1) type 1 -> given L and R find product of integers of array whose indices are in range [L, R] modulo 1e9+7
2) type 2 -> find first digit of product of integers of array whose indices are in range [L, R] without modulo 1e9+7
3) type 3 -> update the value of the array at given index.
Example =
arr = [2,3,4,5,6]
L = 1, R = 5
then for type1 = (2 * 3 * 4 * 5 * 6) % mod = 720
and for type2 = (2 * 3 * 4 * 5 * 6) = 7 (which if the first digit (from left) in 720)
Constraints :
1 <= N <= 1e5
1 <= arr[i] <= 1e9
1 <= Q <= 1e5
1 <= L <= R <= 1e5
I am able to handle type1 and type3 queries easily with segment tree. But having no idea how to handle type 2 queries
Before posting this blog i did some research about this and found one useful link
Link : https://www....
handle type 2 queries Before posting this blog i did some research about this
and found one useful
184.
Helping Students Struggling in Placements and Internships Hello Codeforces,
As resumes are your first impression to the company, all of us want to put our best effort to prepare a FANNG worthy resume which can attract the recruiters to get shortlisted for top tech companies like Google, Facebook, Amazon, Microsoft, Apple, Goldman Sachs etc.
We have prepared a video in which we discuss all the tips and tricks required to create such a resume. We also have shown a resume which get shortlisted for Google, Microsoft, Goldman Sachs, Tower Research, Amazon and D E Shaw.
In this video we have discussed the important components that every resume must-have.
It will clear all your doubts related to:
The best platform to design your resume.
What should be the length of the resume?
How many projects are good to write?
Do the extra curricular activities matter for the coding interviews?
We hope you will like the content and experiences shared. Do like and share the post so that this video can reach and help as many people as possible.
[L...
Research, Amazon and D E Shaw.
185.
Understanding a Compiler-Specific Issue Hi everyone!
I'm having trouble with [my submission for problem 382A.](http://codeforces.com/contest/382/submission/14680749)
The lines in question are commented in the submission above, but I'll highlight them here as well for clarity.
Using the following passes all the test cases:
~~~~~
long long len = w2.length();
len -= w1.length();
len = absol(len-1);
~~~~~
While using this instead fails the first one, but returns the correct answer on my local machine:
~~~~~
long long len = absol(w2.length()- w1.length()-1);
~~~~~
Does anyone have an idea of what's going on at a technical level?
My best guess is that it has something to do with precedence, and that in the second case the function address is being returned instead of the actual length. I'm not sure if this is the problem though and I've never run into something like this before.
I've tried doing a bunch of research on this issue, but haven't yet been able to find the answer. I'm hopi...
I've tried doing a bunch of research on this issue, but haven't yet been able
to find the answer
186.
Sioyek - Academic PDF Viewer Hi!
During my PhD, I developed sioyek which is a PDF Viewer designed for reading research papers and technical books. I think it can be of interest to the users of this site. Here are some of the features:
- Quickly preview or jump to figures/references/equations/etc. (even if the PDF doesn't have links)
- Search paper names in google scholar by middle clicking on their name (you can configure other search engines as well)
- Ruler mode for easier reading and less eye strain (for a demo of this feature, see [this](https://user-images.githubusercontent.com/6392321/168427739-007be805-a457-4d1f-ba14-35c5070aae5f.mp4))
- Searchable table of contents, automatically generate table of contents if not available
- Searchable highlights/bookmarks
- Browser-like history navigation
- Mark locations for quick navigation (Vim style)
- Synctex support
- Extensibility using external scripts (see https://ahrm.github.io/jekyll/update/2022/07/05/implementing-a-screen-reader-for-sioyek.html for...
Hi! During my PhD, I developed sioyek which is a PDF Viewer designed for reading
research papers
187.
Codeforces/DMOJ but for Competitive Math To all those that compete in math contests like the AMC in the US or Euclid in Canada, would you be interested in a platform similar to Codeforces or DMOJ but for competitive math?
A few months ago I was preparing for the Euclid, and wanted to look for a platform similar to Codeforces or DMOJ but hosted virtual math competitions instead, because only doing past problems and mock contests was getting kinda dull. However, I couldn't find any such platform like this. Thinking about it now, competitive math seems to be much more popular (at least at a high school level) compared to competitive programming, yet it lacks any platforms that host online contests, use a rating system, and have an active community. I'm thinking of creating such a platform, but I first wanted to get a sense of what others in the competitive math field thought of the idea.
Would you be interested in such a platform? Why or why not? Do you have any advice/suggestions for developing such a platform?
Also, ...
research skills that I was unable to find a platform that fit my description.
188.
Hitachi Hokkudai Lab. & Hokkaido University Programming Contest 2021 Hello everyone!
It’s our pleasure to invite you to participate in this year’s **Hitachi Hokkudai Lab. & Hokkaido University Programming Contest on Future autonomous distributed city development**. The contest is jointly sponsored by Hitachi Ltd. and Hokkaido University. It is a marathon-type contest which will last for one month and takes place as follows:
- **from November 13th, 2021 to January 31st, 2022 (*Problem B starts on December 4th).**
_We were preparing for the contest starting on November 5th, but the preparation has been delayed due to some bugs found in the development code and we need additional time to investigate them. We are very sorry to inform you that as a result of considering the work period required to maintain the quality of the contest, we have decided to postpone the date of the contest. Your understanding would be greatly appreciated._
The contest provides problems related to optimal area design for a regional energy system. The contest consists o...
For those interested in the research background of the contest, please visit
the following website:
189.
Hitachi Hokudai Lab. and Hokkaido University Contest 2020 Hello everyone!
It’s our pleasure to invite you to participate in this year’s **Hitachi Hokkudai Lab. & Hokkaido University Programming Contest on Future autonomous distributed city development**. The contest is jointly sponsored by Hitachi Ltd. and Hokkaido University. It is a marathon-type contest which will last for one month and takes place as follows:
- **from December 17th, 2020 to January 16th, 2021.**
_Due to the recent spread of COVID-19 infection, we have decided to postpone the date of the contest. Your understanding would be greatly appreciated._
The contest provides problems related to multi-objective and spatio-temporal optimization in uncertain environments. The contest consists of two problems A and B. The winner of each problem will receive 100,000 JPY, and 300,000 JPY, respectively. Registration has opened and is available through the following websites:
- [Hitachi Hokudai Lab. and Hokkaido University Contest 2020](https://atcoder.jp/contests/hokudai-hi...
For those interested in the research background of the contest, please visit
the following website:
190.
Why do you do CP? Here are some reasons I believe people do CP:
- [Enjoyment](https://codeforces.com/blog/entry/45186?#comment-297758)
- Preparation for job (coding) interviews
- Preparation for Competitions
CP seems to be a low priority activity. For example, school and job responsibilities usually take higher priority. It’s not possible (realistically) to make a living from CP. Thus, people taking part in CP usually have good reasons.
The nihilist viewpoint says CP is just solving contrived made-up problems. Who cares? There’s little/no benefit to society. Unlike CP, programming for a job creates services (value) for people. Unlike CP, Computer Science research pushes the boundaries of knowledge of the field (value). Why spend time in an activity which doesn’t product relative value? Again, it seems the people doing CP must have good reasons.
I’m wondering what people’s reasons are for doing CP.
creates services (value) for people. Unlike CP, Computer Science research
pushes the boundaries of, . Unlike CP, Computer Science research pushes the boundaries of knowledge of
the field (value). Why spend
191.
Internships and Ph.D. positions at Indiana University, USA 
Hi all,
We have internships and Ph.D. positions in algorithms and machine learning available at Indiana University, Bloomington, USA. Our group maintains active collaborations with research groups at leading industrial organizations, including Amazon NYC, Facebook HQ and Google (HQ and NYC).
Ph.D. ($20-25K/year): [http://grigory.us/phd-call-f19.html](http://grigory.us/phd-call-f19.html)
Internships ($4K/2mo): [http://grigory.us/gtap.html](http://grigory.us/gtap.html)
Deadline: December 15, 2019.
Our past and present interns and students include [user:Chameleon2460,2019-11-27], [user:dyukha,2019-11-27], [user:josdas,2019-11-27]. For more information on our group and alumni placements, you can check [http://grigory.us/#group-alumni](http://grigory.us/#group-alumni)
Please, feel free to PM if you have any questions.
~~~~~
--
Grigory Yaroslavtsev,
Director of the Center for Algorithms and Machine Learning (CAML),...
University, Bloomington, USA. Our group maintains active collaborations with
research groups at leading, group maintains active collaborations with research groups at leading
industrial organizations
192.
Internship Positions at ISTA Dear Codeforces Community,
The Chatterjee group at Institute of Science and Technology Austria (ISTA) is hiring scientific interns for summer 2024. The group’s research focuses on (stochastic) game theory, formal methods, and program verification.
The target group is mainly the 3rd and 4th year undergraduate students with strong mathematical and algorithmic background. Having prior research experience is a plus.
Internship positions at ISTA are fully-funded and the desired time frame is from July to September 2024 (flexible). Unfortunately, a remote internship is not possible at the moment.
In case you are interested, send your CV and transcript to [email protected] by December 31st.
(ISTA) is hiring scientific interns for summer 2024. The group’s research
focuses on (stochastic, algorithmic background. Having prior research experience is a plus., interns for summer 2024. The group’s research focuses on (stochastic) game
theory, formal methods, and
193.
Problem Recommender System For Codeforces Users Hi Codeforces!
I am really pleased to introduce My research project called PROPER
- This is an web application that recommend you some problems that have adequate difficulty to practice.
After you solve the recommended problems you may give PROPER your feedback that the problem is Hard/Adequate/Easy.
This feedback will be used to make better recommender system.
- System automatically collect status data from CodeforcesAPI, and calculate adequate problems to user personally, Problem is recommended based on your status and other coder's status interactively.
- We use Matrix Factorization algorithm which is one of the famous recommender system model.
the PROPER address is: http://recommender.cf
I've evaluated this system in statistical way and it was quite good.
So I'd like to survey about this system for actual users.
I hope it works well for users and this system helps you practice better.
Thank you for reading!!
I am really pleased to introduce My research project called PROPER
194.
Russian school students took 4 gold medals at the International Olympiad in Informatics (IOI-2019) 
It is a very rare situation at IOI. It happened at IOI-2012 in Montichiari in Italy for the last time.
- Ildar Gainullin (11th grade of the Lyceum named after N. And. Lobachevsky, Kazan Federal University)
- Alexander Morozov (graduate of the Presidential physics and mathematics Lyceum № 239, St. Petersburg)
- Vladimir Romanov (graduate of Moscow state University Specialized educational and scientific center)
- Egor Lifar (10th grade Intellectual school, Moscow)
Russian team took the first place in the medal standings and second — in points am ong 88 countries (more than 330 students participated in the Olympiad).
The selection and training of the national team was held at the Moscow Institute of Physics and Technology second year in a row. Trainers from MIPT, University ITMO, National Research Lobachevsky State University, Moscow State University, Higher School of Economics and Moscow Work...
Technology second year in a row. Trainers from MIPT, University ITMO, National
Research Lobachevsky
195.
For Hire — Categorizing the USACO Problems Hello guys!
It would really useful for me to categorize the USACO problems based on their difficulty and their "USACO Guide" category (Simulation, DFS, segment tree, etc), mirroring what the [USACO Guide](https://usaco.guide/) does but for every problem.
Additionally, there's some interesting room for ML research on AI-based classification. If anyone has experience in that, it would be highly appreciated.
I'm willing **to pay $300** (or more) for someone with the time for this project. If you're interested and are at least decently experienced at competitive programming, please DM me. Thanks!
room for ML research on AI-based classification. If anyone has experience in
that, it would be, Additionally, there's some interesting room for ML research on AI-based
classification. If anyone
196.
IOPC 2017 Techkriti 2017 and samsung research India brings forward International Online Programing Contest (IOPC) with a chance to
grab your pile from INR 1,20,000. This is a rated contest of 3 hrs and will start at 15:00 IST on the 21st of April,2017. There is a little under 12 hours left till the contest starts.
The contest is hosted on codechef.
Contest page : https://www.codechef.com/IOPC2017.
Note that the contest is an individual rated contest on Codechef.
The problem setters are [user:utkarshl,2017-04-21], [user:kaushal02,2017-04-21] and [user:dwivedi,2017-04-21] with [user:triveni,2017-04-21] and [user:dopahkiin,2017-04-21] as testers.
The prize distribution is as follows:
1.The international first,second and third get 20%,17% and 13% of total money respectively.
2.The 4th and 5th positions (international) get 10% & 8% respectively. positions 6-10 get 1.6% each.
3.The first, second and third in India get 10,8 and 6 percentage of total
4. In case if someon...
Techkriti 2017 and samsung research India brings forward International Online
Programing Contest
197.
Hitachi Hokudai Labo and Hokkaido University Contests 2019 Hello everyone!
It’s our pleasure to invite you to participate in this year’s **Hitachi Hokkudai Labo & Hokkaido University Programming Contest on Mathematics for Social Creativity**. The contest is jointly sponsored by Hitachi Ltd. and Hokkaido University and will be held in two independent, consecutive rounds, each of which lasting for two weeks as follows:
- **1st contest: from November 8th to November 21st, 2019**
- **2nd contest: from November 29th to December 12th, 2019**
Both contests provide problems related to spatio-temporal optimization in uncertain environments. The first contest consists of two problems A and B. The second contest of a third problem C. The winner of each problem will receive 100000 JPY, 200000 JPY, and 300000 JPY, respectively. Registration has opened and is available through the following websites:
- [Hitachi Hokudai Labo and Hokkaido University 1st Contest 2019](https://atcoder.jp/contests/hokudai-hitachi2019-1)
- [Hitachi Hokudai Labo and ...
For those interested in the research background of the contest, please visit
the following website:
198.
Top 30 ICPC 2018 teams (based on Codeforces rating) As an addition to [Teams going to ACM ICPC World Finals 2018](http://codeforces.com/blog/entry/57257) I suggest table below
_Updated after Codeforces Round #474_
_Updated after Codeforces Round #475_
| Team | Members | Rating(sum)|
| -------------------------------------------------------- | ------------------------------------------------------------- | ------ |
| Peking University | [user:Syloviaely,2018-04-17], [user:SkyDec,2018-04-17], [user:shanquan2,2018-04-17] | 9172 |
| Moscow State University | [user:LHiC,2018-04-17], [user:V--o_o--V,2018-04-17], [user:gritukan,2018-04-17] | 8786 |
| Seoul National University | [user:zigui,2018-04-17], [user:dotorya,2018-04-17], [user:cki86201,2018-04-17] | 8569 |
| University ...
,2018-04-17] | 6948 | | National Research University Higher School of Economics, ], [user:jasonyik,2018-04-17] | 6948 | | National Research University Higher
School of
199.
The famous egyptian underdog (A story of success.... A story of me) In the last few days , a lot of people were trying to impersonate me , AbdurRahman ElGammal.
I think a lot of people in CF community asked themselves "Who is AbdurRahman ElGammal?" of course NO SURPRISE. Let me tell you about myself so you can know why all those people were impersonating me through these fake accounts.
"They call me life coach or mentor, but I'm just a simple guy with some experience."
As you can see , I am a coach. A really brilliant and amazing coach , the coach of most of Egyptian Legendary Grandmasters on CF like [user:bmerry,2016-06-10] , [user:Xellos,2016-06-10] , [user:Swistakk,2016-06-10] and [user:TsunamiNextYear,2016-06-10] , (and they're also red coders on TopCoder). Of course , My territory expands among a lot of countries (like Iraq , Yemen , Gabon and South Sudan). I think you're wondering why I am so humble and I am saying that I am just a simple guy !! I will tell you my story and you will judge.
I was born in Silicon Valley in 1960. My house...
I've spent around 666 days doing research and I was able to calculate certain
patterns in the
200.
NSE-ISB Codesprint [HackerRank] Hello CodeForces Community!
**I am glad to share that HackerRank's NSE-ISB Codesprint is scheduled on [25th March 2017 at 13:30 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=NSE-ISB+Codesprint&iso=20170325T1330&p1=%3A)**
Go ahead and register now — [National Stock Exchange of India -Indian School of Business Codesprint] (https://www.hackerrank.com/nse-isb-codesprint)
There are some cool prizes on offer:
- The winner will get an ASUS ROG laptop
- Second place gets a 1TB PS4 Pro
- Third place gets a Canon EOS 1200D DSLR Camera
Plus, places 4-10 will get a Raspberry Pi (Kit) and Top 25 winners will also receive cool T-shirts and goodies.
Top 5 Participants will also get to attend the prestigious [Summer research conference] (http://www.isb.edu/summer-research-conference-2016) hosted by ISB on July 28-29
2017.
**Please note that the prizes are only for participants from India**
The duration of the contest is 5 days. Signup now and Spread...
Participants will also get to attend the prestigious [Summer research
conference] (http://www.isb.edu, and goodies. Top 5 Participants will also get to attend the prestigious [Summer
research
201.
Research on Traveling Salesman Hi guys! I'm looking forward to doing some research on well-known Traveling Salesman Problem. However, I never went into implementing this algorithm with some optimizations included as I don't know much about them. I tried googling, hoping to find some good resource of information about research on this particular problem, and was surprised not being able to find a good one. Does anyone know any good free e-book or anything similar which would guide me into details of this problem, as well as some optimizations and implementations, so I can try some of them and try to think about something clever myself, considering this problem? Thanks in advance!
Research on Traveling Salesman, Hi guys! I'm looking forward to doing some research on well-known Traveling
Salesman Problem
202.
Sum of Natural Numbers So I've just been reading that the proof that sum of all natural numbers
1 + 2 + 3 + 4... = -1/12
the mathematical proof is sound but it causes some problems like:
how come the sum of 2 natural numbers is a fraction???
my answer is because we aren't dealing with a natural finite number
but I'm not sure how to mathematically explain it
Any ideas??
(Before you rush into saying that the sum is wrong please do some research)..
(Before you rush into saying that the sum is wrong please do some research)..
203.
About me! First of all, let me introduce myself, I am Arsen and recently I have been working in ITmen as a Network Engineer.
The undergraduate curriculum in Computer Science and Engineering at institute of technology, , Ethiopia introduces me to a wide variety of engineering subjects. Various courses like Artificial Intelligence (Robotics), Programming Languages, Electronics I&II, Software Engineering, System Programming, Micro Processor, Interfacing & Assembly, Algorithm Analysis and Design, Digital Signal Processing, Network and System Security, Digital system, Algorithm analysis and design, Computer graphics and multimedia, Computer Simulation and Modeling provided me with a strong footing in the theoretical concept of Computer Science and Engineering.
While offering both depth and breadth across this field, these courses put into perspective the importance and relevance of Computer Science and Engineering and the application of its fundamentals to the problems faced by the real world. ...
extremely distinguished faculty members, and research facilities are the
factors which have motivated
204.
Free USACO Mock test on Feb 18th, 4-8PM, Pacific Time Hi everyone,
X-Camp Academy will provide a Free USACO Mock test on Feb 18th, 4PM-8PM PT. Open to all, and FREE.
A brief introduction about X-Camp (x-camp.org): we are a silicon valley based institute focusing on foundation buildup for the majority of students, and competitive programming for students who are passionate about competitions.
Since founded in 2017, we have been proud of our systematic curriculum from beginner to master class level. More than 22 USACO Platinum division contestants in the past 2 years.
Top students from USACO Grandmaster Class: 5 students entered US National Camp in the past two years, and 2 current students are among the top 10 from the 22/23 Season Dec Platinum Division.
Some highlights:
a. Mock Test Problems are arranged by X-Camp Academy teaching research team and catch the newest USACO problem trends.
b. Simulation of a real competition environment. Best preparation for what’s to be expected for the coming USACO contest in late ...
a. Mock Test Problems are arranged by X-Camp Academy teaching research team and
catch the newest
205.
About HackerEarth September Circuit '21 Long-Time Contest Hello Codeforces,
I am a 56-year old life-long learner and computer-programming lover with PhD degree in Electronics and Electrical Communications Engineering from Cairo University, Egypt, and with research interest in VLSI CAD algorithms, computer architecture, digital signal and image processing. I joined Codeforces five years ago to encourage my son during his first year in college, and I participate almost regularly in long-time competitive programming challenges as time permits.
I participated last week in HackerEarth September Circuits '21 Long-Time Contest that ended yesterday, and I reached the 4th rank on the [Leaderboard](https://www.hackerearth.com/challenges/competitive/sept-circuits-21/leaderboard/) of the Contest. The approximate problem in the Contest was a variant to the well-known Traveling Salesman Problem (TSP). To my surprise, the first runner-up commented about four days ago that the checker program of this problem was broken and it accepted invalid solutions...
and Electrical Communications Engineering from Cairo University, Egypt, and
withresearch interest
206.
Two Approaches on 2D Segment Trees I was researching about 2d (multi-dimensional) segment trees. Firstly, I've looked [user:PrinceOfPersia,2015-02-13]'s [tutorial](http://codeforces.com/blog/entry/15890), but there wasn't much about 2d segment trees; that's why I've researched a little bit and found [this](http://kaidul.com/2d-segment-quad-tree-problem-solving/) blog.
Even though, [user:PrinceOfPersia,2015-02-13]'s tutorial doesn't tell much about 2d segment tree, it says that every node in main segment tree is also a segment tree. On contrary, other blog describes a totally different idea.
Can someone explain me (or point out a website that explains it) the idea represented in [user:PrinceOfPersia,2015-02-13]'s tutorial and compare (complexity, usages etc.) these two different approaches? Also, it looks like range update with lazy propagation would work with a quad tree. Is lazy propagation possible in other one?
UPD: Thank you really much for good answers! They're really useful.
207.
NUS admission for IOI medalists Hello Codeforces,
Here is my story (skip to next paragraph if not interested). I am 14 yr boy from India.I am currently in grade 9. I am preparing for IOI and aiming for Silver/Bronze medal.
My dream is to get into international colleges like MIT,NUS,etc. But my family is not that much financially strong (my family income was just 3000$ or 3.20 lakh rupees per year).
**So basically I want to know how much scholarship IOI medalists get at NUS,MIT,etc..** and **The total fees for IOI medalists at NUS,MIT,etc..(in numbers or approx estimation in numbers)**.
I will politely request [user:T1duS,2021-11-04] and [user:RestingRajarshi,2021-11-04] to answer about the above question. As they were also from India and currently pursuing CS degree in NUS (Singapore).
<spoiler summary="Dont click:My sad story">
Basically my parents are forcing me to start preparation for JEE. But I am tring to convince my parents that IOI medalists also get good Colleges like NUS,MIT,...
208.
algorithms The Algorithm or Algorithms was named after Muhammad bin Musa Al-Khwarizmi, the Arab mathematician, and what is meant by algorithms in the field of programming are the steps that we use to solve the problems that we meet. And that's it
And of course, there is a basis in his book, the algorithm, not anything, and that's it, I can say about it algorithm
1- Simplicity: This is an important thing in writing any algorithm so that I, as a programmer, can turn it into code that I really use. The simpler the steps you use, the easier it is for you to use them later
2 General: And here what is meant by it is that when I create an algorithm, I do it in a way that I can use it on a large scale. I mean, for example, I can’t say 1 + 2 = 3. This is an algorithm because it has a limited scale, which is only these two numbers. But it is possible that x + y = z is an algorithm. So I can use any number and it will do exactly the same job
3- Efficiency: And here we will need to understand the con...
209.
༆¤๋ࣧࣧ Binary Search on Unsorted Arrays: Slope, Maxima and Minima ¤๋ࣧࣧ༆ Hello CF community,
So recently I came across the [Leetcode Problem](https://leetcode.com/problems/find-peak-element/), where we had to find a peak in the given **unsorted array**. And the most optimized approach was to use Binary Search. Quite interesting concept! I was puzzled so I researched a bit on the topic and came across an interesting term. The Binary hyperparameter search. If you find time, do check [this](https://www.researchgate.net/figure/Binary-hyperparameter-search-A-change-in-the-sign-of-the-slope-indicates-that-there-is-a_fig2_348589572) out. I would also like to know more about such problems where the solutions are interestingly out of the box.
I felt writing this simple blog will help many beginners like me out there who never knew such a concept existed. So please try to share in here or in my DM if you know any such interesting topics which can broaden our knowledge on some well known concept.
Such topics are the reason why I love programming. It challenge...
210.
How to start getting into theoretical CS research from CP ? Hi everyone. I am a third-year student exploring a transition into theoretical computer science research, given my background in competitive programming. I would greatly appreciate any advice from those who have successfully navigated a similar path.
How to start getting into theoretical CS research from CP ?, research, given my background in competitive programming. I would greatly
appreciate any advice from
211.
Struggling to Motivate Yourself to Spend More Time on CP? For anyone struggling with motivation with competitive programming, this video is for you. It is my most researched video yet. I studied the neuroscience behind what is going on when you procrastinate USACO specifically. While this video is made from USACO specifically since that is where I have the most experience, it generalizes nicely to most of cp.
There are a couple of citations from a doctor who studies this, but it is easy to understand. We also have clear steps to break the procrastination habits cycle. I hope you find [this training](https://youtu.be/AZzoVlJb-sw) useful!!
212.
Bug using global anonymous struct in GNU C++11 and GNU C++14 Hi,
I've sent submission [submission:25136808] using a global anonymous struct with some big arrays and methods inside. The submission got RTE case 7.
Next, I send submission [submission:25137642] only removing the struct from around the arrays and the methods, and I got AC.
Then I thought "maybe the global arrays are not being initialized to zero when they are inside the struct". So I called `memset(&st,0,sizeof st);` and I got RTE case 7 again: [submission:25137670].
What's the deal with structs in Codeforces? All these 3 codes work fine I'm my notebook in test case 7.
**UPD**: I've just submitted the same 3 codes again, now with GNU C++14. The behavior is the same for all 3 codes.
**UPD2**: Now I've just submitted [submission:25138080], only giving a name to the struct from the first submission and it got AC. So the problem is with anonymous structs??
**UPD3**: Seems like anonymous structs are not supported in C++ 11, after some Internet research...
**UPD3**: Seems like anonymous structs are not supported in C++ 11, after some
Internetresearch...
213.
Interesting Math Problem Recently I encountered the following problem in the recruitment test for IBM research.
There is an array of size K with elements from 1 to N and an array of size N with elements from 1 to K. Prove that there exists a sub-array of the first array and a sub-array of the second array with the same sum.
I was thinking of applying pigeonhole principle using difference of prefix sums but could not get anything concrete.
Any ideas about how to prove this ?
Recently I encountered the following problem in the recruitment test for IBM
research.
214.
ACM-ICPC Live Archive Bug? I was recently trying to research my chances of qualifying for ACM ICPC by looking at the latest regionals I could find problems for, ACPC 2015, which can be found at the [ACM-ICPC Live Archive](https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&category=677). I had first solved a few of the problems on the [Hackerrank instance](https://www.hackerrank.com/contests/2015-acm-acpc/challenges) before I found the official one, but when I tried submitting my code that solved the Hackerrank instance of them it would give WA on the ICPC OJ.
Also it seems there are no successful submissions whatsoever to the whole contest on the whole OJ which seems suspicious. Does anyone know if the ICPC OJ is known for having wrong test cases? Or is output formatting more strict or something?
As a reference to test it if anyone wants to try to solve the very easiest problem (it's div 2 problem A level) they can try [here](https://icpcarchive.ecs.baylor.edu/index.php?option=com...
I was recently trying to research my chances of qualifying for ACM ICPC by
looking at the latest
215.
Problems that I authored so far Since competitive programming is dying, and I'm almost retired, so it's time to review the problems I authored.
Hi everyone! I wanted to write such a blog for a long time, motivated by similar blogs, [by](https://codeforces.com/blog/entry/113093) [user:antontrygubO_o,2023-02-25], [by](https://codeforces.com/blog/entry/108940) [user:adamant,2023-02-25] and [by](https://codeforces.com/blog/entry/108595) [user:tibinyte,2023-02-25]. This is not a super-comprehensive list. I set many shit problems that I don't want to share for some local contests.
It can be long, and I'm not sure if I have finished half of them yet.
The number of asterisks after the label indicates the recommendation levels. One asterisk means this problem is worth reading. Two asterisks mean this problem is one of my favorite problems, Three asterisks mean this problem is one of my best problems.
| # | Date | Problem | Contest | Comment |
| ---- | ----------- | --------------------------------------------...
216.
Marathon Threads! Inspired by [AoPS](https://artofproblemsolving.com/)'s Marathon Threads, I decided to create one on CF! The only rule of this forum is that you have post an interesting theorem, or trick related to CP or math, with a brief description and provide a source for extra research.
To start things off, I think that Proizvolov's identity is very interesting (but doesn't appear much in math problems :( ) and states if you have the numbers from $1-2n$ and split the numbers into 2 sets $A, B$ such that $A$ is in increasing order and $B$ is in decreasing order, the sum $|A_1-B_1|+|A_2-B_2|+\dots+|A_n-B_n|$ is always equal to $n^2$. Source: [https://en.wikipedia.org/wiki/Proizvolov%27s_identity](https://en.wikipedia.org/wiki/Proizvolov%27s_identity)
CP or math, with a brief description and provide a source for extra research.
217.
A reminder that we pay $10-12/hour for rewriting problem statements Hi,
Wanted to remind the community that we host a project
http://r-nn.com
Where we pay people for rewriting problem statements from online judges into short concise form. Most of the people who participate in the project today average between $10 and $12 per hour.
We use those rewritten statements to teach machines solve competitive programming problems.
We especially need people who can read **Japanese** or **Romanian**!
There's another way you can help tremendously with our effort. We need as many solutions from websites that do not make the submissions public. If you can share with us your account on Timus, SPOJ, e-olymp, acmp.ru, COJ, or any other website on which solutions can be seen after logging in, that would help a lot with our research (in case of COJ you can just download all your solutions on the website in one click and share the downloaded archive).
So far around 20 CodeForces users shared with us their accounts, thanks a lot to all of them!
would help a lot with our research (in case of COJ you can just download all
your solutions on the
218.
Rating Changed 0! Hi CodeForces!
Recently, I've started doing contests on CodeForces and when my rating jumped I was obsessed with contests, ratings,....
I was wondering how do rating changes, is there any rule, or is there any formula... And after some research, I found this site:http://codeforces.com/blog/entry/102.
I was discussing with my pals about one interesting thing, you can not(obviously it is possible) get rating change 0. I mean, there is a very little chance for you to break the formula and get infinity(and beyond!).
I thought that if someone succeed in breaking the formula, CodeForces would give him +1 or -1 or some similar value, oh boy was I wrong! When I finished my last contest (Div 2. #442), which I did terribly (solved only problem A, (average for me is B and sometime C) and one hack), I was waiting for results. The NoButtHurt extension didn't work on me, I thought okay bug, it happens... My friends got their results (and rating change) and I didn't. I was waiting and waiti...
formula... And after some research, I found this
site:http://codeforces.com/blog/entry/102.
219.
Pick elements from an array so that their sum lies within an interval **Update: My coach got back to me and sent me the constraints!** $w_1, w_2, \ldots$ are the elements.
**Subtask 1:** $n \leq 20; w_i \leq 10^9; l, r \leq 10^{15}$
**Subtask 2:** $n \leq 40; w_i \leq 10^9; l, r \leq 10^{15}$
**Subtask 3:** $n \leq 80; w_i, l, r \leq 10^5$
**Subtask 4:** $n \leq 200000; w_1 = w_2 = \ldots = w_n \leq 10^9; l, r \leq 10^{15}$
**Subtask 5:** $n \leq 200000; w_i = i; l, r \leq 10^{15}$
**Subtask 6:** $n \leq 200000; w_i, l, r \leq 10^{15}; r - l \geq \max w_i - \min w_i$
**Update: A helpful user has sent me [an online judge link.](https://oj.uz/problem/view/IOI16_molecules) I can start researching from here. Thanks a lot! Unfortunately, the trollish attitude of downvoters is something I have to put up with. It's a permanent aspect of Codeforces.**
**Edit: The constraints weren't included in the original problem statement! My coach and I failed to solve this problem. I have two RAR archives of test cases for you to judge the validity o...
220.
An awesome list for competitive programming! This is a project I started from late January 2016.
My motive is that: Although there's fantastic information out there, I think they're still spread all over the place. Therefore, in my opinion it would probably be cool if there's an awesome list for competitive programming! ( It's now featured on the main list! )
I'm actively updating the list here: https://github.com/lnishan/awesome-competitive-programming
Awesome Competitive Programming Awesome
A curated list of awesome Competitive Programming, Algorithm and Data Structure resources.
Created with a view to connecting people to information, this list below contains a complete collection of all the fantastic resources I've collected over the course of my 11-year competitive programming career. I hope you'll find it useful :)
What is competitive programming? — Quora
Contributing
Please kindly follow CONTRIBUTING.md to get started.
You can also contribute by sharing!
Share the list with your classmates, your friends and eve...
on various CP blogs. ★☆☆ OLYMPIADS IN INFORMATICS An international journal
focused on theresearch
221.
Need Help on a problem Some crazy white old man, calling himself the “Danger”, after watching a certain T.V series planned to research and invent his own “chemical”. After finishing his recipe, he found out he needs exactly n grams of the main ingredient to make it. If he makes with less than n grams, the mixture is not reactive enough and if he makes it with more than n grams, it simply explodes. He browsed Ebay and found only 2 sellers for the item. Seller A only sells n1 gram containers for c1 rupees each. Seller B only sells n2 gram containers for c2 rupees each. If it’s possible to buy exactly n grams from these 2 sellers, output the minimum cost of buying the ingredients
[Link to the problem](https://www.hackerrank.com/contests/second-years-contest-5/challenges/he-is-the-danger/problem)
I tried using linear diophantine equations, but the solution fails for large inputs.
My approach:
1. ax + by = c
2. find if solution exists based on gcd
3. if exists find any solution to x and y
4. i...
to research and invent his own “chemical”. After finishing his recipe, he
found out he needs
222.
Teams for ACM ICPC World Finals 2015 — Marrakesh, Morocco I'm planning to make a scoreboard for the ACM ICPC World Finals 2015, the scoreboard will contain the TopCoder and Codeforces handles for the contestants. It will be similar to [this one](http://a2oj.com/ICPC.jsp) (but with some more improvements).
Please post the Codeforces handles for the qualified teams here. I'll keep updating this post once I get any new information.
Any suggestions for the scoreboard are welcome for sure.
I'll add all the handles I get in the following table:
| | Country | University | Contestant 1 | Contestant 2 | Contestant 3 |
|:--:|:--:|:--:|:--:|:--:|:--:|
| 1 | Russia | St. Petersburg National Research University of IT, Mechanics and Optics | [user:tourist,2015-05-19] | [user:qwerty787788,2015-05-19] | [user:VArtem,2015-05-19] |
| 2 | Japan | The University of Tokyo | [user:rng_58,2015-05-19] | [user:semiexp,2015-05-19] | [user:wrong,2015-05-19] |
| 3 | China | Shanghai Jiao Tong University | [user:AngryBacon,2015-05-19] | [user:rowdark,201...
| |:--:|:--:|:--:|:--:|:--:|:--:| | 1 | Russia | St. Petersburg National
Research University of IT, Mechanics and Optics
223.
Splay Trees VS Treaps I recently came across a very interesting Data Structure, that to me, was completely revolutionary in how I view data structures. That is, Implicit Treaps. But on to my question: Now that I'm pretty familiar with the implementation of Treaps and its applications, should I learn Splay Trees (I will learn it regardless eventually, but I have a competition coming up and time is limited)? To narrow down the question, are there problems that can be solved with Splay Trees but not with Treaps?
Through a brief research session, I found the following blog from CF that partially answers my question.
https://codeforces.com/blog/entry/60499
Apparently, Link Cut Trees can be maintained with Splay Trees in N log N time while Treaps have an additional log factor. Are there other instances of this?
Through a brief research session, I found the following blog from CF that
partially answers my
224.
Algorithmic Research Project Ideas! I asked my institutes professor if there is any project idea he has in domain of Algorithms. He suggested devise your own or enhance existing encryption-decryption algorithm (eg. RSA, AES, DES) . I am looking for more research project ideas on algorithms if you have any comment down it would be great help.
Algorithmic Research Project Ideas!, am looking for more research project ideas on algorithms if you have any
comment down it would be
225.
MIT Theory Blog Hi everyone!
We have just started a student blog of MIT Theory of Computation Group. If you are curious to read or gossip about "real" research in Theoretical Computer Science or life of graduate students, feel free to sign up!
- Blog: http://mittheory.wordpress.com
- RSS: http://mittheory.wordpress.com/feed
- Twitter: https://twitter.com/notsogitcs
The blog is run by:
- [Alon Cohen](http://toc.csail.mit.edu/user/138)
- [Ilya Razenshteyn](http://www.ilyaraz.org)
- [Aaron Sidford](http://www.informatik.uni-trier.de/~ley/pers/hd/s/Sidford:Aaron)
- [Prashant Vasudevan](http://toc.csail.mit.edu/user/152)
- [Henry Yuen](http://www.mit.edu/~hyuen/)
or gossip about "real" research in Theoretical Computer Science or life of
graduate students, feel
226.
How to get started with AI/ML as a competitive programmer? Learning AI is a bit overwhelming.
There are so many theories and constant new research. Competitive programmers are generally good at learning new concepts because we like to learn with a hands-on approach.
But can that same **hands-on approach** be applied to **learning AI?**
I'm sharing details of a new product, **specifically built** to make AI learning easy for **competitive programmers**: **[AIcrowd Blitz⚡](https://www.aicrowd.com/blitz)**
Blitz is a no-nonsense approach to learning AI. It works in a very simple way:
- You get a new real-world AI puzzle in your inbox every two weeks
- The puzzle teaches you the core ML concepts and guides you on how to solve it
- Every two weeks, you join in for an expert live call to understand state-of-the-art techniques for your solution
So, the learning happens on autopilot while you get hands-on with solving the puzzle.
Pretty sweet, eh? You can find more information about Blitz [**here**](https://www.aicrowd.com/bl...
There are so many theories and constant new research. Competitive programmers
are generally good at
227.
How do you guys get an internship? Dear Codeforcers,
I am an international student who is currently studying at UNSW Sydney. I am doing a double degree of advanced maths and computer science. I have been doing informatics Olympiad in my high school and ACM-ICPC atm. As Summer(for Australia) holiday is approaching, I am really interested in finding a software engineer internship at Sydney. However, I did some research and without exaggeration, every company requires residency(permanent residency or citizenship). Some companies only hire graduating students.
Is there any suggestion you guys can give me? That would be very appreciated!
Kind Regards
interested in finding a software engineer internship at Sydney. However, I did
someresearch and
228.
Minimum edges to delete to make shortest paths intersect On my research I came across the following problem.
Given a weighted graph G = (V,E,w) and four nodes s1,t1,s2,t2 find the minimum number of edges that need to be deleted from G so that the set of shortest paths from s1 to t1 and the set of shortest paths from s2 to t2 have at least one edge in common.
I have been trying to prove that this problem is NP-hard but I was not able to come up with anything. Does anyone have any idea?
On my research I came across the following problem.
229.
How do I get a 2-3 subgraph or 3-4 subgraph? (Research question) Hi, I am writing my bachelor thesis and I came across a study which mentions finding a 2-3 subgraph and a 2-4 subgraph of an undirected graph as one of its subtask but it doesn't mention an algorithm to do it but it just says that it is done using DFS.
I couldn't really find anything useful online solving these problems.
A 2-3 subgraph is a subgraph where each node has degree 2 or 3 in this subgraph (we remove edges which go to nodes outside the subgraph) and our task is to find a maximal 2-3 subgraph (it doesn't have to be maxmimum in terms of size just that we can't add another node to it). A 2-4 subgraph is just the same but with 2, 3 and 4.
Can anyone help by describing an algorithm or linking an article/paper?
How do I get a 2-3 subgraph or 3-4 subgraph? (Research question)
230.
Future researches for new data structures Hi Codeforces!
I have finished my bachelor's degree in computer science a few months, and I intend to keep studying in a master's degree. I really like problems with data structures, and I would like research this topic or something like that.
So, What kind of new data structure do you think that need to be create for the future? What kind of problem would this structure solve?
like research this topic or something like that. So, What kind of new data
structure do you think, studying in a master's degree. I really like problems with data structures,
and I would likeresearch this
231.
Codechef-crawler | Tool to download all codechef solutions ## Codechef-Crawler
While doing lots of Competitive programming, I decided to contribute for open source. After doing lots of research I thought why not I start with codechef. Therefore, I make my own tool in **Python** which is completely open-source.
Codechef-Crawler is a tool to download all your code submission from codechef.com and store them locally with a well-structured manner. Please refer below link to know more about its usage.
**Github**: [https://github.com/bansal1232/Codechef-Crawler][1]
##Features
1. Download all solutions from **Practise** and **Contest** section of codechef.
2. Solutions are downloading by using Multithreading concept which makes it faster to download in parallel way.
3. Open-source
4. It's Cross-platform which makes it to execute in any operating system.
##Screeshots:
##Credits
Used idea from [https://github.com/koldbyte/CodeBackup][3]
##Cont...
lots of research I thought why not I start with codechef. Therefore, I make my
own tool in **Python
232.
Thoughts on Round 928 (Div. 4) After a busy weekend rowing abroad, it was finally time to get back to coding. By skipping one of my lectures on heaps, I managed to make it back home and join the contest only 20 minutes late, ready to solve some easy problems.
The contest went way worse than I expected — I only solved A and B. It might just be coping, but I think problems C and D were too difficult for Div. 4 — they felt Div. 3 level at the very least. I spent a good while trying to find some patterns on C, but couldn't manage to put together a solution. For problem D, I didn't notice very important key details and spent considerable time researching how to use bitsets, but even after I figured out how to read the bits of numbers, the solution I had didn't work and would probably have been too slow anyway. While doing problem E, I made a mistake when I came up with my algorithm to solve it, which turned out to be a major flaw that made the whole algorithm useless. It's a bit sad that I will most likely...
233.
how to proof x & -x is a power of two don't larger than x Im learning BIT (Fenwick tree), i saw a expression that is `x & -x` to find largest power of two don't larger than x.
But i can't clear this expression, please tell me the truth. Thank you very much!
I searched google and don't have any more knowledge that `it is a trick.`
I asked GPT but it have just give example but don't proof. I've just known that this expression is a trick :'( and no more.
And more, could you give me some bitwise-research-documents? I hope that learn more about bitwise, thank you.
And more, could you give me some bitwise-research-documents? I hope that learn
more about bitwise
234.
Link Cut tree Question !! I am learning link cut tree. I have seen the research paper and other slides.
But i have a question about this DS. Can LC Tree answer the number of childs under a root's subtree efficienty ? I mean, if I link root of a tree under a node, then if i ask the number of child under the great root, which is root of all the nodes. Can LC answer the question efficiently ? If yes, then how ? How can I propagate the value to all the ancestors ? I have seen one implementation here:
[submission:860934]
How to modify it ?
Thanks in advance. :)
I am learning link cut tree. I have seen the research paper and other slides.
235.
Is CP useful to prepare students for academic research (in computer science, of course)? Hi again! I'd like to ask if competitive programming is useful as a preparation for computer science research, specially in the field of data structures and algorithms. If yes, what skills are the most used? I hope someone working in academia could tell me in which way CP helps or helped him/her in his/her regular work.
Thanks in advance <3
Is CP useful to prepare students for academic research (in computer science, of
course)?, science research, specially in the field of data structures and algorithms. If
yes, what skills are the
236.
[Research] LLL Algorithm - Yet Another Paper-Reading Problem So apparently after ML problems we are getting crypto problems in ICPC...
Link: [https://zhtluo.com/cp/lll-yet-another-paper-reading-problem.html](https://zhtluo.com/cp/lll-yet-another-paper-reading-problem.html)
[Research] LLL Algorithm - Yet Another Paper-Reading Problem
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