announced score distribution in Codeforces history. **UPD** The final decision
on scheduling is, bright side, this may be the earliest announced score distribution in
Codeforceshistory.
Rating changes for last rounds are temporarily rolled back. They will be returned soon.
→ Pay attention
→ Streams
→ Top rated
| # | User | Rating |
|---|---|---|
| 1 | jiangly | 3640 |
| 2 | Benq | 3593 |
| 3 | tourist | 3572 |
| 4 | orzdevinwang | 3561 |
| 5 | cnnfls_csy | 3539 |
| 6 | ecnerwala | 3534 |
| 7 | Radewoosh | 3532 |
| 8 | gyh20 | 3447 |
| 9 | Rebelz | 3409 |
| 10 | Geothermal | 3408 |
→ Top contributors
| # | User | Contrib. |
|---|---|---|
| 1 | maomao90 | 174 |
| 2 | awoo | 164 |
| 3 | adamant | 163 |
| 4 | TheScrasse | 159 |
| 5 | nor | 158 |
| 6 | maroonrk | 156 |
| 7 | -is-this-fft- | 151 |
| 8 | SecondThread | 147 |
| 9 | orz | 146 |
| 10 | pajenegod | 145 |
→ Find user
→ Recent actions
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.
History
Last visit:
2 months ago
Registered:
6 years ago
2.
Codeforces Round #639 Hello, Codeforces!
I'm very glad to invite you to [contest:1344] and [contest:1345]. This contest will take place on [contest_time:1344]. In both divisions, you will have **2 hours 15 minutes** to solve **6 problems**. The score distribution will be announced closer to the start of the contest.
Of course, this round would not be possible without the help of many people, who I'd like to thank:
- [user:isaf27,2020-05-01], for coordinating this round, and helping with solution ideas.
- My ICPC teammates [user:Kuroni,2020-05-01] and [user:strongoier,2020-05-01], and coach [user:cn355,2020-05-01], for encouraging me to pursue competitive programming. In particular, I'd like to thank [user:Kuroni,2020-05-01] for being so spectacularly bad that a barely-orange user like myself actually has a place on our team.
- [user:300iq,2020-05-01], [user:antontrygubO_o,2020-05-01], [user:Ari,2020-05-01], [user:ffao,2020-05-01], [user:fpc_coder,2020-05-01], [user:gamegame,2020-05-01], [user:Kur...
Announcement of Codeforces Round 639 (Div. 1)
Announcement of Codeforces Round 639 (Div. 2)
3.
Hello 2019 Hello coders! I hope that you are enjoying the New Year as much as me. To make its beginning even greater, Codeforces is going to host a contest and I will be an author of all tasks. Hello 2019 will take place on [Friday](https://www.timeanddate.com/worldclock/fixedtime.html?day=4&month=1&year=2019&hour=17&min=35&sec=0&p1=166).
Using the opportunity, I want to thank to:
- [user:lewin,2019-01-02] and [user:mnbvmar,2019-01-02] for testing the round.
- [user:mnbvmar,2019-01-02] for indescribably helpful discussions about problems.
- [user:_kun_,2019-01-02] and [user:KAN,2019-01-02] for round coordination and help with preparation.
- [user:MikeMirzayanov,2019-01-02] for such great platforms (you know which ones :P).
The round will consist of 8 problems and you will be given <s>two and a half</s> three hours to solve them. Yes, the round will be **rated**.
There will be no interactive problems, but if you want you can read [this](https://codeforces.com/blog/entry/45307) docum...
about the people who already have or had their part in Codeforces' history. As
I wanted to be, decided to write statements about the people who already have or had their
part in Codeforces'history
Announcement of Hello 2019
4.
Goodbye 74TrAkToR + Problem A~E: The problems themselves are good and typical A~E. Indeed I like problem D. The pretest for A is a bit weak, and it's not a big problem yet.
+ Problem F: The problem has an origin. :) See the link: [click](https://www.luogu.com.cn/problem/P9394). The problem in contest is only a weakened version of the one in Luogu.
+ Problem G: It's said that our great coordinator had not proved the time complexity of the intended solution is correct :) If the authors did, please share it in the editorial. (although this problem is completely beyond my ability :) )
+ Problem H: Oh dear [user:74TrAkToR,2023-12-30], could you please OEIS the sequence before you use the "several-integer-input" problem in
rounds next time? Anyone who copied the first example and opened [https://oeis.org/A286331](https://oeis.org/A286331) could quickly get the formula. And the problem itself is not so hard imo. Anyway, it should not be used in contest, especially for the last problem.
For me pers...
In Year 2023, 74 had coordinated $10$ rounds in total. Here's, in my entry. He just said, "it's all history". :), . He just said, "it's all history". :) **Edit4:** According to [Appeal.
74TrAkToR](https
5.
Self-deception: maybe why you're still grey after practicing every day I generally don't like to give much advice on "how to practice", but recently I have been thinking a lot about this and I realized that there is something that I believe affects a lot of people (though it is admittedly hard to tell) that barely gets talked about: self-deception.
Self-deception is a devious thing. It can be very hard to detect, yet can be fatal to improvement.
This blog is mainly directed to greys, greens and cyans that can't get out of these categories. Most examples are given with that in mind. That being said, I believe others have something to think about as well.
This is my first blog on such "psychological issues" and I don't know if I'll ever make another one. It's certainly a difficult topic to write about because for most of the blog, the message is "your practice is not as good as you think it is" or even "you aren't as good as you think you are" which can of course be a hard thing to hear. Thus, I have to somehow be very gentle while getting the poin...
Let me tell you something about my practice history. Somewhere in late 2019 and
early 2020 I, ] Let me tell you something about my practice history. Somewhere in late 2019
and early 2020 I
6.
Competitive Programming Hall of Fame — cphof.org Hi Codeforces!
Today I'd like to introduce the new [Competitive Programming Hall of Fame](https://cphof.org) project that is available at [cphof.org](https://cphof.org)
#### Background
A long time ago I've noticed that there is no single source of information with the results of previously held large programming competitions. Moreover, plenty of older championships don't maintain their websites anymore, and it becomes hard or even impossible to find any details about them, which is pretty sad. So I've decided to create [Competitive Programming Hall of Fame](https://cphof.org).
#### About the project
Competitive Programming Hall Of Fame is a project created to preserve the history of international championships in competitive programming. This website collects the results of the final stages for both worldwide and regional contests. By international championship we mean a contest consisting ...
creating resources that share our mission to preserve the history of
competitive programming contests, project Competitive Programming Hall Of Fame is a project created to preserve
thehistory of, Competitive Programming Hall Of Fame is a project created to preserve the
history of international
7.
When will Codeforces end? The last mark in the updated ranking history As you know, Codeforces recently added the ability to scroll through the user's rating history. I decided to take this opportunity to find out how long this wonderful service plans to exist.
To do this, I went to my page, looked at my rating
<spoiler summary="Spoiler">
and began to cry
</spoiler>
Next, I began to zoom out as much as possible. At one point, I got something that looked like the flag of Indonesia.
After zooming out a bit more and scrolling a bit to the right, I found that at some point new divisions stop being added. To be more precise, this is about the 251st millennium:
It seems that we are close to a solution! It remains only to zoom in to see a more accurate value.
So, 275760 is, apparently, the last year of Codeforces' existence!
Let's zoom in even more to get the accuracy up to a mont...
When will Codeforces end? The last mark in the updated ranking history, As you know, Codeforces recently added the ability to scroll through the user's
ratinghistory. I
8.
About the Round 382 Good afternoon!
I've decided to share my thoughts on the round 382.
Of course, it turned upset not only to me, but also to the round coordinator [user:GlebsHP,2016-11-28].
In this round the main negative feedback were caused by two problems: [problem:735D] and [problem:735C].
Regarding [problem:735D]. I do not share the criticism to this problem. In fact, to solve it would be nice to be familiar with <a href="https://en.wikipedia.org/wiki/Goldbach's_conjecture"> Goldbach's Conjecture</a> and better with <a href="https://en.wikipedia.org/wiki/Prime_number_theorem">Prime Number Theorem</a>. These facts are medium-popular in the world of programming contests. Familiarity with them is useful, gives useful insight into primes. It is important: in this problem it was necessary to perform a simple, but nevertheless, additional step to find solution. It seems to me that it's okay to use problems that have a reduction to some popular and semi-popular topics. Otherwise, it is th...
the view that it would be better not to be so, but history has already taken
place. Note that if I, would be better not to be so, but history has already taken place. Note that
if I learned the situation
9.
[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...
**Considering that the vast majority of the evidence comes from the commit
history of NaokiLH
10.
ICPC Regionals — The Chennai flood and the Asia Director Background
----------
One of the regionals in India was scheduled to be held at [Hindustan University](http://icpc.hindustanuniv.ac.in/) at Chennai on December 17 — 18, 2015. Unfortunately Chennai was stuck by a [natural disaster](https://en.wikipedia.org/wiki/2015_South_Indian_floods). The entire south India received heavy rainfall and hence there was a lot of flooding at many places including Chennai around that time. Atleast 347 people died in the state of Tamil Nadu (where Chennai is located). The damage due to the floods overall in south India is estimated to be atleast USD 3 Billion. It is the costliest flood in 2015.
Ofcourse, due to this the Chennai regionals was postponed. I think everyone here will agree that this was an unexpected, unprecedent situation and hence it was entirely understandable that the regionals was postponed.
The Blog post
-------------
Dr. C J Hwang is the ICPC Asia director. In response to the above postponement he posted a blog article...
-ICPC Asia history, we never had the case of contest postponement."_ Comment:
That is just luck, _Quote from the blog: "In the 20 years of ACM-ICPC Asia history, we never had
the case of contest
11.
Codeforces: Results of 2017 <img src="/predownloaded/e4/09/e40915ee54c5991b91098756a90270d94be893b3.jpg"/>
Happy New Year, Codeforces!
I hasten to wish the whole community (and including me) correct programs, sudden insights, beautiful ideas and interesting problems!
I hope that you have met the new year at least as fun as I am. Have you had enough sleep after New Year's Eve? This year, the traditional post summarizing the past year, I sat down to write only on January 1, 2018. I hope that I will not have to sum up the whole year.
This post is important to me, since it draws a line to all the work done by the Codeforces team and the entire community in 2017. Many thanks to the team: all of the achievements listed below are the result of joint efforts. We did an excellent job! The community must know its heroes. In 2017, [user:MikeMirzayanov,2018-01-02], [user:KAN,2018-01-02] (problem coordinator), ~gritukan,2018-01-02 (second problem coordinator), ~netman,2018-01-02 (ex-second problem coordinator), ~k...
for freezing, etc.). 1. A tag about an atypical problem (*special). 1. Show the
history of, freezing, etc.). 1. A tag about an atypical problem (*special). 1. Show the
history of communication
12.
You won't believe how this simple trick defeated the unexplained bug destroying every top LGM ### TL;DR
Currently people are discussing a slowdown bug on Codeforces that seems to happen randomly, and can cause code to run 100x slower and get TLE. More details in [user:pajenegod,2024-03-03]'s [blog post](https://codeforces.com/blog/entry/126654).
In this article, I present a mitigation: add the following to your code.
~~~~
#include <windows.h>
void *operator new(size_t size) {
if (void *ptr = HeapAlloc(GetProcessHeap(), 0, size ? size : 1)) return ptr;
throw std::bad_alloc{};
}
void operator delete(void *ptr) {
HeapFree(GetProcessHeap(), 0, ptr);
}
~~~~
<spoiler summary="If you use malloc/free in C++ (you shouldn't), also change them.">
~~~~
void *my_malloc(size_t size) {
if (void *ptr = HeapAlloc(GetProcessHeap(), 0, size ? size : 1)) return ptr;
throw std::bad_alloc{};
}
void my_free(void *ptr) {
HeapFree(GetProcessHeap(), 0, ptr);
}
~~~~
</spoiler>
<spoiler summary="If you use aligned new/delete in C++, also change the...
slowdown bugs in Codeforces history is the poor implementation of the C
runtime.
13.
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...
/subtract operations in $O(1)$ or $O(\log n)$ 2. Transform history max/min/sum
queries into interval
14.
My sad story Teams advancing to 2016 WF Phuket in Asia have been announced recently. This announcement is undisputedly tantamount to a death sentence for me. I am the one waiting anxiously, refresh Dr. Hwang's blog everyday. But it seems that for years, our training was meaningless.
I think many of us dedicate our passion to programming contests because we see them transparent, fair and without any corruption. And I also believe that as contestants, what we should do is only focus on the practice. And I thought those political business should never come to bother me one day. But sadly, it is my team who is going to become one of the sacrifices of a succession of the dissension.
What happened so far
------------------
The quarrel between the Asia director and the local community is [a long story](http://blog.sina.com.cn/s/blog_b946da100101q21y.html) to tell. But it has never been as serious as it was in the past season. Now reflecting on this, I know on the surface everything is going okay...
ICPC history, Dr. Hwang had done great contribution to bring this event for
us. But As times alter, chance to enter final. As far as I know, there is no team in our region in
history which get 2nd, far as I know, there is no team in our region in history which get 2nd place
but cannot go to final, the ICPC history, Dr. Hwang had done great contribution to bring this event
for us. But as times alter, . As far as I know, there is no team in our region in history which get 2nd
place but cannot go to
15.
Looking For EDU Lecturers <img src="/predownloaded/47/86/4786c2ec901c0b5b490794ca6fd5145f0dcdeae3.png" style="float:right; width: 400px; margin: 0 1em 1em 1em"/>
Hello!
I always like to think that Codeforces is not only a place where you come to compete but also a place where you can learn. Learn new things.
Two years ago, we launched the [EDU](https://codeforces.com/edu/courses) subproject, a platform for publishing classes. There are already several classes, but there are so many interesting topics around!
The Codeforces team can write the platform, make the technical foundation, but it would be great to write content with the support of the community.
Thanks to the support of competitive programming alumni, we have a budget for targeted grants for the preparation of new classes in the EDU section. Hope we have new content soon!
We are looking for lesson authors who could prepare and record one or more lessons. Those who are now red or have ever been red are invited.
We assume that one le...
lessons to understand the expected format and structure of lessons. We have a
richhistory of, of lessons. We have a rich history of teaching, so you can count on our advice
and assistance in, We invite you to help grow the community and make history. I am sure that the
recorded classes will
16.
Opinion: Don't Waste Problems on Div 2 **History Lesson**
Let's take a look at the solve count for the last problems in the last 4 division 2 contests:
803 (Div. 2): F (7 official solves); G (2 official solve)
802: E (18 official solves): F (11 official solves)
801: E (1 official solve)
Edu 130: F (2 official solves)
There's a trend. The last and hardest div2 problem frequently has very few official solves. This means that the last problem, despite taking a lot of time to create, doesn't really affect rankings that much. The authors spent much time for a problem that didn't make a big difference. But it would've made a difference in div1.
Personally, I think that it's okay if 20 or even 30 people AK a div2 round, so it's okay to have 20-30 people solving the last problem. Then, you can take those hard problems and insert them into a div1 round. That way, we can have more contests.
Basically, make div2 last problems a little easier, that way we can save those hard problems for another contest.
What...
**History Lesson**
17.
Testlib: tests + CI Hello, Codeforces.
I have wanted for a long time and now, finally, I sat down and did it.
Many of you are familiar with my [Testlib](https://github.com/MikeMirzayanov/testlib) project. This is a library that helps you develop problems if you are using C++.
In the case of problems for Codeforces rounds, its use is mandatory. It seems to me that it is almost a de facto standard for preparing materials for completely different olympiads and competitions.
The history of С++-Testlib is almost lost in centuries, I published the first version in 2005.
Nowadays, making edits to Testlib has become tricky. The code grown to thousands of lines, also it has too long a history.
This increases the likelihood of accidentally changing some aspect of behavior, which will jeopardize the holding of a Codeforces round or another important competition.
In short, making a bug in this code or changing behavior anywhere is highly discouraged.
So I recently took the plunge and wrote some test...
has too long a history. This increases the likelihood of accidentally changing
some aspect of, materials for completely different olympiads and competitions. The history of
С++-Testlib is, The history of С++-Testlib is almost lost in centuries, I published the first
version in 2005.
18.
Codeforces: Rating Is Fixed (bug, go away!) Hello!
Last weeks I was concerned (and probably, you too) about abnormal rating growth of our leaders. Of course, first of all I'm talking about [user:tourist,2016-04-06], his rating is just rushed into the sky.
[ ](http://codeforces.com/predownloaded/99/59/9959129ab312a0bd0923600541211a1246a5201b.png)
There were even comments from a series of "I told, and it happened"
After the first round of VK Cup 2016, I carefully investigated the reasons of such growth and found a simple and trivial bug in the rating formulas. It's funny that even after being published, nobody found it. Look at this function:
~~~~~
private double getSeed(List<Contestant> contestants, Contestant contestant, int rating) {
Contestant extraContestant = new Contestant(null, 0, 0, rating);
double result = 1;
for (Contestant other : contestants) {
result += getEloWi...
history.
19.
How to use Codeforces [GUIDE] I see a lot of newcomers struggling to use the website to it's fullest, so I decided to write a blog that has all important information about how to use Codeforces in a single place. I will update it with time, so feel free to write your suggestions/questions in case I missed something and I will be glad to add it to the post!
I would like to thank [user:_Vanilla_,2022-02-05] and [user:mesanu,2022-02-05] for helping me write the blog, and [user:Monogon,2022-02-05], [user:down,2022-02-05] and [user:AlperenT,2022-02-05] for proofreading and giving suggestions.
#### Navigating through pages
It's possible to navigate through most pages of Codeforces using the bar on the top, I will talk about what each tab does more in depth below:
#### The Help Page
The help page contains the answer to a lot of questions about Codeforces, such as rati...
This page also contains "Contest history" which has all past contests that
happened on the website
20.
On Div2ABs 2 years ago, [user:antontrygubO_o,2022-04-27] wrote [a blog](https://codeforces.com/blog/entry/75163) about div2ABs where he expressed his opinions that d2ABs should not be about "here is a statement, please implement what is written there". Thanks to him, the quality of d2ABs (and problem quality in general) have certainly improved. However, I still believe that there still quite large differences between how coordinators/problemsetters view d2ABs and how the intended participants view them.
From the survey made by [user:kpw29,2022-04-27], we can see that most people agree that most people agree that we should **primarily** consider the target audience when proposing a task. I too think if a task is boring to div 1 contestants, we should not think of that as a reason to immediately disqualify a problem from being a d2A.
I think when people judge the interesting-ness of d2As, they try...
history
21.
Bayan 2015: Finals [Final scoreboard](http://contest.bayan.ir/en/contest/final_2014/scoreboard/)
[Introduction](/blog/entry/17541)
[Arrival](/blog/entry/17631)
[History](/blog/entry/17633)
[Some photos from contest and closing ceremony](/blog/entry/17733)
Interview with Bayan CEO Ali Ghadiri and some photos from the event will be published tomorrow
Places 10-15 received bronze medals
Top 3 receive gold medals. Silver medals for next several places: 4. Adrian Budau 5. Peyman Jabbarzade 6. Pooya Zafar. Places 7-9 also received silver medals, unfortunately I could not keep up with announcers
Nikola Djokic is third!
Ali Haghani is second. Congratulations!
And the winner is Evgenii Kapun aka ~eatmore,2015-05-02
Winners will be announced shortly!
Speeches, videos and performances — all the usual things for closing ceremony.
Closing ceremony is underway. We'll know winners shortly
Scoreboard is frozen
|Place|Name|Country |A |B |C|D |E|F|G |H |Score|
|-...
[History](/blog/entry/17633)
22.
The Second Revolution of Colors and Titles Over the last several months the Codeforces team has been looking anxiously at the inflation in the rating caused by both an influx of new users and the imperfect calculating formulas.
In the end it lead to noticeable shifts in colors and titles. For example, getting red in 2015 became much easier than in 2013.
We conducted a [survey about the way to introduce the color bounds](/blog/entry/20629). We are happy to announce the updated colors and titles!
A summary of the main changes goes like that:
* a new color: greenish-blue color or cyan — just like the name implies, this color takes its place between green and blue, now the participants of the second division will be better differentiated;
* all the colors shift upwards along the rating scale — see the table below. Now reaching the top positions will be harder;
* the legendary grandmaster — the new title and color for those who reached the sky high rating 2900.
The cold colors (gray, green, cyan an...
rich history of participations in order to become a coach. Problem tags and
groups can be added by
23.
XXII Open Cup: GP of EDG Hello! I'm happy to announce XXII Open Cup: Grand Prix of EDG, which will be held on Nov 14th, 2021.
This contest is mainly prepared by Zhejiang University, which has already been used as the 2021 CCPC Guilin Contest.
On the same day of the 2021 CCPC Guilin Contest, Team [Edward Gaming (EDG)](https://en.wikipedia.org/wiki/Edward_Gaming) from [League of Legends Pro League (LPL, China)](https://en.wikipedia.org/wiki/League_of_Legends_Pro_League) won the Champion of [the 2021 League of Legends World Championship](https://en.wikipedia.org/wiki/2021_League_of_Legends_World_Championship) held in Reykjavík. They are also the only LPL team entering the semi-finals while the rest of three teams all coming from [League of Legends Champions Korea (LCK, Korea)](https://en.wikipedia.org/wiki/League_of_Legends_Champions_Korea), including the champion from last year. Almost nobody would bet on their winning, but they made it and reclaim the glory for LPL after 2 years.
![ ](https://news.cgtn...
and the strong will push them go forward. Now they make the history. Their
spirit moves everyone and, ![ ](https://news.cgtn.com/news/2021-11-07/EDG-overcomes-past-to-make-history
-with-LoL-Worlds-2021, ://news.cgtn.com/news/2021-11-07/EDG-overcomes-past-to-make-history
-with-LoL-Worlds-2021-victory-14ZSxT2Rp3a
24.
Codeforces Team To Do List ***This blog is to list common bugs/suggestions/complaints for [user:MikeMirzayanov,2022-09-09]. Share your ideas in the comments so I can add them to the list.***
- Make offical dark mode.
- Add discussion section for each problem in the editoral.
- Add unrated registeration.
- Make upvotes and downvotes changable.
- Rename "friends" to "followers".
- Add report user option.
- Add the dislike button([dislikes:1]).
- Change hacked code verdict to "Verdict"(hacked) instead of just "Hacked".
- Problem submission syncing *(i.e. if you solve a problem in a mashup or a div 2, your submission will show up in the div 1 version of the problem as well)*.
- Seperate show tags and show problem rating options for problemset.
- An option for excluding tags when filtering problems *(for example, let's say I want to do some DP problems, but I don't want greedy proble...
25.
I compiled a list of almost all useful blogs ever published on Codeforces [update: till 09.06.2021] <h3 style="color:red">If there are any blogs that I have missed, please tell in the comment section. Thank you.</h3>
# Mathematics Stuff
- [Number Theory in Competitive Programming [Tutorial]](https://codeforces.com/blog/entry/46620)
- [Number of points on Convex hull with lattice points](https://codeforces.com/blog/entry/62183)
- [FFT, big modulos, precision errors.](https://codeforces.com/blog/entry/48465)
- [Number of ways between two vertices](https://codeforces.com/blog/entry/19078)
- [Mathematics For Competitive Programming](https://codeforces.com/blog/entry/76938)
- [FFT and NTT](https://codeforces.com/blog/entry/19862)
- [Burnside Lemma](https://codeforces.com/blog/entry/51272)
- [Number of positive integral solutions of equation 1/x+1/y=1/n!](https://codeforces.com/blog/entry/76836)
- [On burnside (again)](https://codeforces.com/blog/entry/64860)
- [Simple but often unknown theorems/lemmas/formula? Do you know?](https://codeforces.com/blog/entry/55912)
- [Probabili...
wiki dedicated to competitive
programming](https://codeforces.com/blog/entry/50528) - [Thehistory, ) - [The history of some recurring
problem](https://codeforces.com/blog/entry/62331) - [An alternative
26.
[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...
? The answer is that they are what you want them to be. The history behind your
learning process
27.
Polynomial Round 2022 (Div. 1 + Div. 2, Rated, Prizes!) Hello, Codeforces!
<img alt="Polynomial" src="https://codeforces.com/predownloaded/31/39/3139af7f9a6628da7d4b7ce4353a192cf59ee3f5.png" style="float:right;height: 250px; margin: 10px; max-width:50%;"/>
Winter holiday is coming! And we are excited to invite you to our third round, [contest:1774], which will be held on [contest_time:1774]. You are given **8 problems** and **2.5 hours** to solve them.
All problems were written and prepared by [user:Ecrade_,2022-12-14], [user:Little09,2022-12-14], [user:ChthollyNotaSeniorious,2022-12-14], [user:DataStructures,2022-12-14], [user:Cirno_9baka,2022-12-14], [user:mejiamejia,2022-12-14] and me.
And thanks to [user:dorijanlendvaj,2022-12-14], [user:gisp_zjz,2022-12-14], [user:gamegame,2022-12-14], [user:triple__a,2022-12-14], [user:Chenyu_Qiu,2022-12-14], [user:Suiseiseki,2022-07-25], [user:q-w-q-w-q,2022-12-14], [user:leukocyte,2022-12-14], [user:waaitg,2022-12-14], [user:Kubic,2022-12-14], [user:LHQing,2022-12-14], [user:zrmpaul...
of Polynomial. We prefer passionate, quick learners with a history of
excellence.
Announcement of Polynomial Round 2022 (Div. 1 + Div. 2, Rated, Prizes!)
28.
Hosting IOI 2022 is already stressful -- I plead everyone not to make us more stressful **Disclaimer: all opinions written in this post are purely personal and not tied with any affiliation, organization, or institutional I am working with, including but not limited to the IOI 2022 organizers.** Several members within IOI 2022 organizers might even try to prevent me from posting this.
Dear IOI Community in Codeforces,
I am writing in Codeforces this time, not in e-mails or IOI 2022 website since I am writing this in personal capacity and should not reflect a formal opinion of the IOI 2022 organizers.
As you all might know, IOI 2022 will be conducted hybrid -- it will be hosted onsite, but we understand that it is impossible for some countries to come to Indonesia due to the [current global pandemic](https://en.wikipedia.org/wiki/COVID-19_pandemic), so these countries are still allowed to officially participate online.
I am going to be very honest and transparent in this post.
This is the first time the IOI has a hybrid setting like this.
This poses huge chal...
this of, I will claim that Indonesia is the best IOI Organizer ever in the
history of IOI.
29.
Time to Change: Your Feedback Is Important to Us Hooray! Soon there will happen several updates on Codeforces affecting rating and colors. The second Revolution of Colors and Titles is coming!
You will soon find out a new rating with public formula, new color bounds and even something more...
New bounds will fix the rating inflation of last year, it will return exclusivity of high rating and titles. Don't worry if you end up with lower color; it's a new reason for you to move forward!
While discussing the ongoing change we faced an issue about how to apply new colors with two possible solutions.
#### First solution: forward without looking back.
When applying new bounds we will update colors everywhere according to a new schema. For example, somebody can possibly lose not only the read color, but he may also regain a new challenge "to become red" since he lost time when he was red before on his rating history.
For the first time it doesn't seem as a good solution, but if you think deeper, there is nothing bad in it...
confirmed by your rating history., new challenge "to become red" since he lost time when he was red before on his
ratinghistory. For, red" since he lost time when he was red before on his rating history. For the
first time it, #### Second solution: keeping history., We did like this before it worked not bad, if we have changed the color history
back then, it would
30.
[Feature request] Some suggestions for blogs I wanted to suggest some improvements for the blog system. Some of these things have probably been said before. Some of these things should be pretty easy to implement, others are harder and might require a complete rework. I tried to put the easy things first.
[cut]
$~$
#### Let's do something about necroposting
This is probably my biggest pet peeve about Codeforces blogs. Most of the time, Recent Actions is filled with very old blogs, some of which have been brought up for pretty much no reason at all. Currently, we have [useful C++ "library](https://codeforces.com/blog/entry/8387) from 2013 in Recent Actions, where the recent comment answers an old question which has already been answered better. Similarly, there is [How to add friends?](https://codeforces.com/blog/entry/2006) which was brought up to make some joke that has already been done.
The thing is though, a lot of the time these blogs are not brought up by trolls or anything like that. They are brought up by hel...
something along these lines, you can edit the blog and disallow viewing history
, but you won't delete, , you can edit the blog and disallow viewing history, but you won't delete
other people's thoughts by
31.
Thank you for participating in the AtCoder World Tour Finals 2022 English (translated by GPT-4):
To AWTF2022 Contestants,
Thank you so much for participating in the contest. I apologize for not being able to communicate much due to my inability to speak English. Did you enjoy the contest event? I look forward to seeing you again in Japan.
To Everyone,
With the conclusion of the topcoder open (TCO) and Google Code Jam (GCJ), and the decision to hold Meta Hacker Cup 2023 online, the only on-site contest in 2023 where anyone from around the world can participate and truly determine the world's best is the AtCoder World Tour Finals.
I have participated in the topcoder open finals 5 times (Marathon division) and in the Google Code Jam finals once. Both tournaments were outstanding. From my experience as a competitive programmer, participating in these competitions has been significant, and I believe that this culture must continue.
The AtCoder World Tour Finals is a budding event. Compared to TCO and GCJ, it has a shorter history, and th...
AtCoder World Tour Finals is a budding event. Compared to TCO and GCJ, it has
a shorterhistory, and, The AtCoder World Tour Finals is a budding event. Compared to TCO and GCJ, it
has a shorterhistory
32.
My story at ACM ICPC World Final 2016 My team (me + [user:flashmt,2016-05-20] + [user:nguyenhungtam,2016-05-20]) was probably never noticed by anyone, but we were actually aiming for medal. And I think we performed ok in the final, ending up at #15, still need some more luck & brain to win a medal. Anw, I decided to share my story. Btw if you are Vietnamese, you can also read [this](https://www.facebook.com/notes/thanh-trung-nguyen/t%C3%B3m-t%E1%BA%AFt-acm-world-final-2016/1157851804228014?pnref=story).
Back story
==========
In the ACM history, a Vietnamese team has never won any WF medal. 5 years ago, team of [user:ktuan,2016-05-20] (only Vietnamese red target on Topcoder) had high hope, but ended up at #17. 4 years ago, team of [user:ConanKudo,2016-05-20] also had high hope, but messed up in the first 3 hours and ended up at #17.
So I really wanted to win medal. And I've been planning for this World Final for several years..
Team formation
==============
I've chosen [user:flashmt,2016-05-20] as teamm...
========== In the ACM history, a Vietnamese team has never won any WF medal. 5
years ago, team of, In the ACM history, a Vietnamese team has never won any WF medal. 5 years ago,
team of [user:ktuan
33.
Codeforces Updates (April-May, 2015) Hello!
Codeforces never sleeps, and I am going to tell you about our recent updates which weren't announced yet.
### Testlib
- testlib moved to [GitHub](https://github.com/mikemirzayanov/testlib), and the version 0.9.9 with C++11 support has been released.
### Polygon
- Added basic support for test groups. Now you can specify group for each test, run invocations by test groups, and you can view summary for each group on the invocation page. If group is specified for a test, it will be added to the problem descriptor (i. e. `<test cmd="gen 1 2" group="testGroup" method="generated"/>`).
- You can now view problem statements and validator for a problem/contest on the same page. This makes finding mistakes in translations and in validator much easier (before you had to open them on separate tabs and switch between them, which is not comfortable). On the problem statements page the "Review" link has been added:
<br/>
 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.
35.
Asking for help FAQ What to do when you need help with a problem?
1. If there is an editorial, read it.
If you don't know some technique, google it and read a tutorial.
2. Ask a friend for help.
It's very useful to find someone in your university/country who also does competitive programming.
3. _"I'm getting WA and don't know why."_
Try to find a counter-test.
Take an accepted code if it's available, and write a brute force otherwise.
Test it against your solution on thousands of random tests, especially small ones.
4. _"My code doesn't work on this test."_
Use some debugging tools (google them for your OS/IDE) or just print values of everything you compute. I use gdb and valgrind. Simulate the program on paper too. This way you should find an exact place where something incorrect happens, or you will see that your approach is completely wrong.
5. _"The output differs on my machine and in Codeforces/anotherPlatform."_
It's likely "undefined behavior", e.g. you don't initialize a local...
main account. I prefer answering people that use Codeforces and have some
non-empty contesthistory., prefer answering people that use Codeforces and have some non-empty contest
history. > "How to train
36.
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...
have done this without your help. Im genuinely super happy. Have a great night
everyone,history has
37.
Codeforces Round #318 [RussianCodeCup Thanks-Round] Hello Codeforces community!
Codeforces Round #318 (for both divisions) will take place on [August, 29 at 19:30 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=29&month=8&year=2015&hour=19&min=30&sec=0&p1=166).
It is the Thanks-Round devoted to Russian Code Cup.
You will be given 5 problems and 2 hours to solve them.
Scoring will be announced close to the round.
I strongly recommend you to read all problems.
<a href="http://www.russiancodecup.ru/">RussianCodeCup</a> is the largest open programming competiton for Russian-speaking participants by Mail.Ru Group. Its history started in 2011. And since the first championship RCC offers great problems and generous prizes. This year finals will be held on September, 19th. Wish good luck to all the finalists! Thank you, RussianCodeCup, for your gift on the 5th anniversary of Codeforces!
I am honoured to be a problem setter ...
competiton for Russian-speaking participants by Mail.Ru Group. Its history
started in 2011. And since the, largest open programming competiton for Russian-speaking participants by
Mail.Ru Group. Itshistory
Announcement of Codeforces Round 318 [RussianCodeCup Thanks-Round] (Div. 1)
Announcement of Codeforces Round 318 [RussianCodeCup Thanks-Round] (Div. 2)
38.
View the history of top10 in Codeforces! The video is [here](https://www.bilibili.com/video/av43450831/) (uploaded by myself).
[user:Anguei,2019-02-14] helped me upload it [on YouTube](https://youtu.be/nfAnKzyiKTo).
Thank [user:I_love_Tanya_Romanova,2019-02-14] for pointing out my mistake of ignoring the inactive users. I have fixed it now.
I get the rating history of each user **who is in the top5000 either of the active or the inactive now** by Codeforces API. So if a user was in the top10 but is in neither the top5000 of the active nor the inactive now, he will not be included in the historical top10s.
I made the video using [Dynamic Ranking Visualization](https://github.com/Jannchie/Historical-ranking-data-visualization-based-on-d3.js). And the codes written by me is [here](https://github.com/ouuan/Get-CF-Historical-TOP10).
P.S. The numbers change continuously in the video, so the ratings in the picture are not the exact value.
P...
View the history of top10 in Codeforces!, it now. I get the rating history of each user **who is in the top5000 either
of the active or, I get the rating history of each user **who is in the top5000 either of the
active or the inactive
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...
Central and Eastern Europe, with over 175 years of history., history. 150 students from 53 universities, including ITMO, University of New
South Wales, St
40.
Educational Codeforces Round 128 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1680] [contest:1680] 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,2022-05-12] Dalabaev, Vladimir [user:vovuh,2022-05-12] Petrov, Ivan [user:BledDest,2022-05-12] Androsov, Mak...
gold and silver** for the first time in its history and will go to the ICPC
World Finals, history and will go to the ICPC World Finals. Congratulations to all of our
participants and coaches that
Announcement of Educational Codeforces Round 128 (Rated for Div. 2)
41.
Dear Russian friends — a personal message from Germany Hi, I'm Gregor. I've been to 17 countries for coding competitions, including two ICPC world finals (judging from my color here, I must have had some really good teammates...). I've never posted here before, but I love this open community, and due to the current situation, I'd like to convey this message to all my Russian friends here:
I'm from Germany. As you will know, eight decades ago, my country, ruled by the nazis, has brought the greatest horrors upon the jewish people and upon the entire world. Adolf Hitler, and countless millions who followed him, fought against the entire world, without any justification other than to gain more territory and power, and committed crimes so cruel and gruesome they go beyond anyone's imagination. Estimated 60 — 80 million people were killed, many more lives around the world were upended. Instead of providing a better future for their children, parents had to bury them. My own great-grandparents fought and died, I presume vicously and ful...
a bond through our common history. I'd like to assure you: people in Germany
are deeply aware of the, adressing this past because we all share a bond through our common history.
I'd like to assure you, And it must be stopped. Being aware of our history, we all know this,
rationally and deep in our
42.
The history of some recurring problem Hi everyone! This one will be long and contain a lot of off-topic, prepare yourself (or skip down to solution of mentioned problem)!
### Intro
In this blog post I would like to talk about some problem that somehow was on my mind for several years and yet only now I have some more or less complete understanding of how to deal with it. The problem is as follows:
_You're given string $S$ and $q$ queries. In each query you have to count amount of distinct substrings of $S[l,r]$._
[cut]
<br><br>
Since then and for a long time this one was probably the hardest string problem I could ever imagine. In particular I saw some partial cases of it on several judges, which supported my assumption that problem is particularly tough. Some notable examples:
- [To Queue or not to Queue](https://www.codechef.com/problems/TMP01) on codechef by [user:Gerald,2018-08-24]. It is the same problem, but queries are formed as queue, i.e. you have to add letter to the right, delete letters from th...
The history of some recurring problem
43.
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 has a long history of working on program synthesis. Here are
two good, __Programming from examples__ has a long history. One known example that you
can run in your
44.
First Ever Users to Reach Some Rating Milestones Revised: ratings above 1500 and greatest falls Several days ago I published a [table](https://codeforces.com/blog/entry/104320) with first people to reach certain ratings. It was a bit raw because, firstly, it was based on top 20000 Codeforces users by rating, and, secondly, because it only gave information about ratings divisible by 50. Now I have prepared a table that is of more complex design, but both issues are resolved. Good luck understanding what is going on in it.
[cut]
For several reasons I firstly put another table. This is the table of greatest rating falls in the history of Codeforces. The reasons are:
1. I have collected so much data from Codeforces that it would be blasphemy not to use it in as many ways as possible.
2. These tables might intersect a lot: it's easier to get a terrific fall in ratings if you are high-rated.
3. Someone recently posted a table with greatest rating rises and falls. I wasn't able to find this table to check whether it was right, but if someone finds it, you're welcome to pu...
history of Codeforces. The reasons are:
45.
Cormen Medal 2013 After a short delay (but Oscar is given in spring too, huh?) we are pleased to announce the Cormen Medal laureates for 2013. This year, we’ve decided to slightly upgrade nominations again, so this year's Cormen Medal is given in two nominations:
* Best Progress
* Best Problemsetter
## Best Progress
<center>
<img src="http://assets.codeforces.com/images/cormen-2013/scott_wu.jpg">
</center>
The Cormen Medal laureate in this nomination is Scott Wu ([user:scott_wu,2014-05-12], USA). Note the [sharp upward dive his rating line takes](/profile/scott_wu). His achievements in 2013 are not limited by the spectacular dive into the best 10 participants on Codeforces: he got the 5-th place on IOI, won the 2013 season of the USACO contests, got target on TopCoder! We congratulate Scott and wish him many more achievements!
## Best Problemsetter
<center>
<img src="http://assets.codeforces.com/images/cormen-2013/Sereja-small.jpg">
</center>
We didn't have to search far and ...
## History
46.
[Tutorial] On lambdas, C++ and otherwise: the what, the why, and the how **Disclaimer:** This blog (and all of my other blogs, unless specified otherwise) is 100% ChatGPT-free — there has been no use of any AI/ML-based application while coming up with the content of this blog.
<spoiler summary="The reason and an appeal">There is a lot of AI-generated content out there these days that sounds plausible and useful but is absolute garbage and contributes nothing beyond a list of superficial sentences — even if it has content that is true (which is a big IF, by the way), it generates content that you could have just looked up on your favorite search engine. The reason why such current AI-generated content is like this is multi-fold, but I won't get into it because I need to write the content of this blog, too, and I don't see copy-pasting this kind of content as anything but a stupid maneuver that wastes everyone's time.
I hope other people who write blogs refrain from using this stuff for generating content that is supposed to be meaningful an...
computation and some history. And, of course, I will make a few philosophical
arguments along the way
47.
Educational Codeforces Round 75 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1251] [contest:1251] 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 **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-10-23] Glazov, Adilbek [user:adedalic,2019-10-23] Dalabaev, Vladimir [user:Vovuh,2019-10-23] Petrov, Ivan [user:Bl...
knowledge and stories about the history of Codeforces._, stories about the history of Codeforces._ _We are happy to offer a special
price of **1,000 EUR
Announcement of Educational Codeforces Round 75 (Rated for Div. 2)
48.
Group tutoring Hi. I offer classes for groups of 2-3 students.
I teach competitive programming with a focus on problem-solving.
There won't be many lectures because I can send you an article/video link instead.
The lesson cycle is usually: I choose a problem, you say your thoughts and ideas, I comment on incorrect ideas, and we talk about the valid solution(s), possibly with drawings and pseudocode.
In beginner groups, I might ask you to implement something, C++ or Python preferred.
There's a lot of homework and you're expected to practice a few hours per week.
We might spend half a lesson talking about 1-2 homework problems from last week.
This is intended.
We use Google Meet, shared whiteboard, and a collaborative editor Codebunk.
After a lesson, you get a video recording and a codebunk with code/text history like this one https://codebunk.com/pb/3501100331621/.
This allows you to copy links and code easily.
There's a Discord group chat to ask questions between classes.
- 1.5h les...
get a video recording and a codebunk with code/text history like this one
https://codebunk.com/pb, with code/text history like this one https://codebunk.com/pb/3501100331621/.
This allows you to copy
49.
Editorial Round 1 of Yandex.Algorithm 2018 <spoiler summary="Police Patrol">
First, let's try to find the largest block that two patrols can cover (hint, it's not k). For instance, we can have one patrol cover $1,2,\ldots,k$. and the other cover $2,3,\ldots,k+1$.
So, we can split $n$ houses into blocks of length $k+1$. Now, we have to look at what to do with the leftover houses. If there are more than two empty blocks, we need two patrols to cover both blocks. If there is only one empty block, we only need one patrol. Thus, the answer can be computed by the formula in the code below
<spoiler summary="code">
~~~~~
n,k = map(int, raw_input().split())
print (n/(k+1))*2 + min(2, n%(k+1))
~~~~~
</spoiler>
</spoiler>
<spoiler summary="Alphabetic Subsequence">
We can check that this is equivalent to counting the number of permutations of $0,1,2,\ldots,9$ that appear in $s$.
There are two solutions:
<spoiler summary="solution 1">
Just do it. This is O(10! * |s|) ~ 3*10^8. This is fast enough in some languages.
...
; if (history[a].size() > history[b].size()) { swap(a, b, ; scanf("%d", &s); --s; history[s].push_back(i); } pw2[0] = 1; for, for (int i = 0; i < n; i++) { if (AF[i] != 0) { assert(!history[i].empty, vector history[N];
50.
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...
/subtract operations in $O(1)$ or $O(\log n)$ 2. Transform history max/min/sum
queries into interval
51.
Educational Codeforces Round 38 — Editorial <spoiler summary="A. Word Correction">
Hint: When does some vowel stay in string?
<spoiler summary="Solution">
Iterate over the string, output only consonants and vowels which don't have a vowel before them.
[Model solution](https://pastebin.com/J0py2Gef)
</spoiler>
</spoiler>
<spoiler summary="B. Run For Your Prize">
Hint $1$: It's never profitable to go back. No prizes left where you have already gone.
<spoiler summary="Hint 2">
Hint $2$: The optimal collecting order will be: some prefix of prizes to you and the other prizes to your friend (some suffix).
<spoiler summary="Solution">
You can find the total time with the knowledge of the prefix length. The final formula is $\min(a_n - 1, 10^6 - a_1, \min \limits_{i = 1}^{n - 1} (\max(a_i - 1, 10^6 - a_{i + 1})))$.
[Model solution](https://pastebin.com/mKhxYUxK)
</spoiler>
</spoiler>
</spoiler>
<spoiler summary="C. Constructing Tests">
Hint: At first we will solve the problem mentioned in the statem...
Hint $1$: Count the number of times each number appears in the
52.
Codeforces Round #479 (Div. 3) Hello!
[contest:977] will start on [May 6 (Sunday) at 14:05 (UTC)] (http://www.timeanddate.com/worldclock/fixedtime.html?day=6&month=5&year=2018&hour=17&min=5&sec=0&p1=166). It will be the first Div.3 round in the history of Codeforces. You will be offered 6 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
[Remember] (/blog/entry/59228) t...
Div.3 round in the history of Codeforces. You will be offered 6 problems with
expected difficulties, in the history of Codeforces. You will be offered 6 problems with expected
difficulties to compose
53.
Yet Another Rating System for CodeForces Finally, I finished the implementation of an improved version of TrueSkill rating system that [user:EbTech,2020-07-04] named "TrueSkill from St.Petersburg".
TL;DR
=====
Results are [here](https://raw.githubusercontent.com/nikgaevoy/SPbTrueSkill/master/data/CFratings_actual.txt). Full repository is [here](https://github.com/nikgaevoy/SPbTrueSkill).
Important notes on the results
------------------------------
Note that those results were obtained by running on the [user:EbTech,2020-07-04]'s testset (rounds only before Codeforces Round #645 and team contests excluded) and thus do not represent the current standings on Codeforces. Also, the file contains only users with at least 10 contests and at least one contest in 2020 (otherwise, the file would be very large). However, you may obtain full rating by running the algorithm on your computer, it should take about a minute. Also note that the results may seem not very impressive since I chose the first parameters out of the ...
- It is very fast. As I have already mentioned, it processes almost all
Codeforceshistory in less
54.
Yet more thoughts on recent "adhoc/constructive" problems discussion. What is the ideal contest distribution? (this was originally intended as a comment to another post, but it turned out very lengthy, so I separated it into its own post)
As it's often in debates, I think in this one there is too much polarization on both sides (people just attack each other), and a lot of ambiguity. I think there are some points to be made.
Premise
-------
1. Let's be kind to each other. Like it or not, this is just a current trend in the history of Codeforces, and it too will pass. No need to attack anyone personally. If you want to criticize, let's provide constructive suggestions.
2. I've set contests before too, and I know that setting problems and coordinating is a very difficult job. It requires a lot of hard work, skill, experience, and patience. So like Anton's and other coordinators' style or not, let's not forget that they have done a lot of work, and let's thank them for that. Thank you!
3. It's also very mean to single out one person for the possible issue. While Anton may have...
1. Let's be kind to each other. Like it or not, this is just a current trend in
thehistory of
55.
First Ever Users to Reach Some Rating Milestones Revised: ratings below 1500 and greatest rises Several days ago I published a [table](https://codeforces.com/blog/entry/104320) with first people to reach certain ratings. It featured only ratings above 1500, and [user:adamant,2022-07-09] advised to do the same, but on achieving ratings below 1500. I found it quite interesting, and, after several days of collecting data about participations of 447911 Codeforces users, I finally made this table.
[cut]
For several reasons I firstly put another table. This is the table of greatest rating rises in the history of Codeforces. The reasons are:
1. I have collected so much data from Codeforces that it would be blasphemy not to use it in as many ways as possible.
2. These tables might intersect a lot: it's easier to get a terrific rise in ratings if you are low-rated. (Many people abuse this and deliberately get very low-rated to make a great jump.)
3. Someone recently posted a table with greatest rating rises and falls. I wasn't able to find this table to check whether it was...
history of Codeforces. The reasons are:
56.
System marks KACTL LCA code as cheating for many participants After competing today in [contest:1304], I received the following message from [user:System,2020-02-15]:
_Attention!_
_Your solution [submission:71152328] for the problem 1304E significantly coincides with solutions [user:ksun48,2020-02-15]/[submission:71134293], [user:hoke_t,2020-02-15]/[submission:71152328], [user:Venia,2020-02-15]/[submission:71156816], [user:hanga97,2020-02-15]/[submission:71159069]. Such a coincidence is a clear rules violation. Note that unintentional leakage is also a violation. For example, do not use ideone.com with the default settings (public access to your code). If you have conclusive evidence that a coincidence has occurred due to the use of a common source published before the competition, write a comment to post about the round with all the details. More information can be found at http://codeforces.com/blog/entry/8790. Such violation of the rules may be the reason for blocking your account or other penalties. In case of repeated violations, your ...
online well before the beginning of the round (check the Git commit history).
You can see that, history). You can see that [user:aryanc403,2020-02-15], a tester for
[contest:1304], used the exact same
57.
Ten years of competitive programming 3 Hey Codeforces!
I’m AmirReza PourAkhavan, the former Codeforces Contest Coordinator. I let the story become complete and I’m sharing it now.
The story is about a 16-year competitive programmer, who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals, twice.
Read the previous post [here](https://codeforces.com/blog/entry/108838).
**Read the Persian version** [**here**](https://docs.google.com/document/d/e/2PACX-1vSUoFC9tLgDCji6rSCYy-RYoUG1_6uOQnHz_LlLKe6KksWBYWO4r6clDly5YxIgzu1g3Tj31weDxgWz/pub).
What happened previously
===
I was a lone programmer, in a small city, trying to learn CP and prepare for the Iran national olympiad. It was not as successful as I expected. I tried to change my school and I migrated to Tehran, alone. I entered AE high school to learn from its inspiring teachers.
11th grade
===
First day of school. I got to ...
collection gathered for any competitive programming class in history. On the
first day of our coding
58.
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...
all contests in CodeChef’s history using Elo-MMR. DMOJ took this approach; it
better leverages the, available under open licenses. 5. **Fast:** on a modern PC, CodeChef’s entire
history is processed, 5. **Fast:** on a modern PC, CodeChef’s entire history is processed in under 30
minutes; using
59.
IOI 2017, first round <center><a style="font-size:20pt;" href="http://scoreboard.ioi2017.org/Ranking.html">Live Results</a></center>
Hi everybody!
I am writing this post from a sunny Tehran where the 29th International Olympiad in Informatics is being held. Me and Mikhail [user:Endagorion,2017-07-30] Tikhomirov are here as a part of Russian Federation delegation on the Olympiad.
In about four hours the first round of the main competitive programming school student event of the year starts. Russian Federation is presented by one of the youngest team ever in the history of Russia on IOI consisting of:<br />
Vladimir [user:voidmax,2017-07-30] Romanov, Denis [user:Denisson,2017-07-30] Shpakovskiy, Alexandra [user:demon1999,2017-07-30] Drozdova and Egor [user:egor.lifar,2017-07-30] Lifar.
In Russian version of this post me together with [user:Endagorion,2017-07-30] are going to make a text coverage of what is happening on the contest. We will mainly concentrate on Russian delegation there, so we ar...
Federation is presented by one of the youngest team ever in the history of
Russia on IOI consisting of:, year starts. Russian Federation is presented by one of the youngest team ever
in thehistory of
60.
Preview: Moscow State University Let’s start with previewing some teams that will participate in World Finals. I will write about 6 teams that I believe are favorites to win gold medals, but anything can happen. Feel free to post your top 6 (top 3, top 12, top n) in comments.
Photo by Yan Tsench
First to go is Moscow State University team ST. It's name has become a brand that has a very long history. My own team, Moscow SU x13, competed against a team with the same name. It usually consist of Moscow SU students that are originally from Saratov.
This is the second time this lineup participate in World Finals. Last year they were 10th and won bronze medals. With last minute (more like last 5 seconds) submission they got 2nd place in last NEERC, which is repeat of 2011 performance. They won last Moscow subregionals.
In last 6 seasons of OpenCup the...
become a brand that has a very long history. My own team, Moscow SU x13,
competed against a team with, history. My own team, Moscow SU x13, competed against a team with the same
name. It usually consist
61.
What not to say when you are accused of cheating `Hi! I got a message stating that "Your solution 123456789 for the problem 9999H significantly coincides with solutions tourist/987654321, jiangly/987654322."`
Anyone who has looked that [that one blog](https://codeforces.com/blog/entry/8790) has seen numerous comments like this. Obviously, except for a few cases, no change has been carried out.
Of course, sometimes you didn't cheat, and you followed all the regulations. **False positives happen.**
Here are some things that you **shouldn't** (and **should**) say in order to make a genuine request for Mike to review your case.
### 1. do **NOT** over-emphasise your rating.
"pls pls pls give my rating back (emoji) i need it i was so close to expert"
First of all, it feels fake.
Besides, obsessing over rating is a common trait of cheaters — if you aren't cheating, you can get the rating back in a few rounds anyways. What's the worst that could happen? You could get back anyways, _if you aren't cheating._
### 2...
good impression. Final thing: your history has a great impact on your CP
career. If you cheated, Final thing: your history has a great impact on your CP career. If you cheated
once, your
62.
A Manual Evaluation of AlphaCode2 through stalking AlphaCode2 accounts See https://twitter.com/cHHillee/status/1732868066558792189 for the original tweet. Contents mimicked below.
TL;DR: I found AlphaCode2 accounts, and through stalking their submission history, I manually performed the AlphaCode2 Codeforces evals, and found the model to perform at about a ~1650 rating.
I am somewhat concerned about data leakage, see https://twitter.com/cHHillee/status/1732636161204760863. This is an AlphaCode2 contributor's response https://twitter.com/RemiLeblond/status/1732677521290789235 However, for the purposes of this analysis I'll take the results at face value.
Methodology
==================
Disclaimer: I'm trying to reverse-engineer info from their public submissions, so apologies in advance for any errors.
There is a fixed set of 12 contests that they submit to. When they kick off a "run" they submit to these contests from several accounts at a time.
 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 ...
about half an hour to simulate the entire history of Codeforces on a modest
laptop; it can be made, A Brief History of Contest Ratings --------------------------------------
Contest rating systems
64.
EZ Collections, EZ Life (new Java library for contests) Hello guys,
I'm going to tell you about one of the negative aspects of Java on programming contests (actually, not only on contests), or, more precisely, how I have tried to resolve it. As you may know, Java has the disadvantage related to its collections library: the constraints of this language make you use object types even when using primitive types should be enough. Compare `ArrayList<Integer>` and `vector<int>`: Java list stores objects of type Integer, which are created every time when you add an element into the list (it's called boxing / unboxing), whereas C++ vector just stores ints. This behaviour slows down Java programs, and many people don't like it.
All this shit comes from the language design: you can't simply write a primitive type inside the angular brackets in Java. Some months ago I was thinking about this problem and came to the solution: why not just write my own collections library, with primitive types? Moreover, I haven't found any library with really all...
#### Version history:
65.
Interactive Problems: Guide for Participants Sometimes you can meet _interactive problems_ on programming contests (including Codeforces).
In problems of this type, the input data given to your program may be not predetermined but is built specifically for your solution. Jury writes a special program — _interactor_, such that its output is tranferred to the input of your solution, and the output of your program is sent to interactor’s input. In the other words, your solution and the interactor exchange the data and my decide what to print based on the "history of communication".
When you write the solution for the interactive problem it is important to keep in mind that if you output some data it is possible that this data is first placed to some internal buffer and may be not directly transferred to the interactor. In order to avoid such situation you have to use special `flush` operation _each time_ you output some data.
[cut]
There are these `flush` operations in standard libraries of almost all languages. Fo...
to print based on the "history of communication". When you write the solution
for the, what to print based on the "history of communication".
66.
Codeforces Beta Round #98 (Div. 2): Editorial <p><a href="http://codeforces.com/contest/137/problem/A" style="font-size: 1.4em;">A. Postcards and photos</a></p> <p>We will move from the left of string to the right. When we passed the whole string, or in the hands of us have 5 pieces, or current object is different from what we hold in our hands, we remove all the items in the pantry. The answer to the problem is the number of visits to the pantry.</p> <p>The complexity is O(n).</p> <p><a href="http://codeforces.com/contest/137/problem/B" style="font-size: 1.4em;">B. Permutation</a></p> <p>We can count the number of integers from 1 to n, which occur in sequence at least once. Then the answer is n minus that number.</p> <p>The complexity is O(n).</p> <p><a href="http://codeforces.com/contest/137/problem/C" style="font-size: 1.4em;">C. History</a></p> <p>Denote a[i], b[i] - ends of the i-th event. Let's sort pairs (a[i], b[i]) by a[i] and iterate over all pairs. Denote rg the maximal b[i] from already processed. If current b[i] <...
C. History <http://codeforces.com/contest/137/problem/C>
Tutorial of Codeforces Beta Round 98 (Div. 2)
67.
Codeforces Beta Round #61 (Div. 2) <div><div>Hello!</div><div><br></div><div>I invite you all to take part in significant round! Today will be the first round for second division in Codeforces history, when it will be rated for blue coders!</div><div><br></div><div>This time the problems are written by me and <span class="Apple-style-span" style="border-collapse: collapse; font-family: verdana, arial, sans-serif; font-size: 13px; "><a href="http://codeforces.com/profile/sdya" title="Lieutenant colonel sdya" class="rated-user user-red" style="font-family: arial; text-decoration: none !important; font-weight: bold; color: rgb(0, 0, 204); ">sdya</a></span>. </div><div>We thank Artem Rakhov, Maria Belova and Dmitry Matov for help in preparing of this round.</div><div><br></div><div>Good luck for all!</div></div><div><br></div><div><b>UPD #1</b>: Congrats to <span class="Apple-style-span" style="border-collapse: collapse; font-family: verdana, arial, sans-serif; font-size: 13px; line-height: 20px; "><span clas...
division in Codeforces history, when it will be rated for blue coders!, will be the first round for second division in Codeforces history, when it
will be rated for blue
Announcement of Codeforces Beta Round 61 (Div. 2)
68.
CodeForces Round 872(Div. 1&2) Editorial ## A. LuoTianyi and the Palindrome String
Consider the substring of $s$ from the second character to the last, or $s_2s_3\cdots s_n$. If it's not palindrome, then the answer must be $n-1$. What if it's palindrome? This implies that $s_2=s_n$, $s_3=s_{n-1}$, and so on. Meanwhile, the fact that $s$ is palindrome implies $s_1=s_n$, $s_2=s_{n-1}$, etc. So we get $s_1=s_n=s_2=s_{n-1}=\cdots$ or that all characters in $s$ is the same. In this situation, every subsequence of $s$ is palindrome of course, so the answer should be $-1$.
<spoiler summary="Code">
```cpp
#pragma GCC optimize(3,"Ofast","inline")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//#define ll int
#define ft first
#define sd second
//#define endl '\n'
#define pb push_back
#define ll long long
#define pll pair<ll,ll>
#define no cout<<"NO"<<'\n'
#define no_ cout<<"No"<<'\n'
#def...
$x$, 2. query the history sum(sum of values on all previous editions). We can
maintain the segments, and $O(m)$ range history sum queries, now the problem can be solved in
$O(n\log n)$ time complexity
Tutorial of Codeforces Round 872 (Div. 1)
Tutorial of Codeforces Round 872 (Div. 2)
69.
overwhelmed **Note: it's a mile-long wall of text about my story in the recent ICPC Regional Contest, which is my first time experiencing it, so if I wasted anyone's time, I'm truly sorry.**
<spoiler summary="Backstory">
I kinda lost motivation in Competitive Programming for a while and decided to take a long hiatus since March. I had a lot of work to study and do, given semesters and stuff, and preparing to go to university (I'm 18). It wasn't fun back then. Fast forward to June, when everything was done, I had a bunch of universities to choose from, and it really messed up my mind. Every school felt, equal. It took like a whole 2 months before I chose Hanoi University of Science and Technology (HUST), most probably because it's well-known in Vietnam and has a long and successful history and stuff.
I knew that it was really hard to not choose Vietnam National University (VNU), since it's a really good school and most of the strongest people in programming, especially CP, went there. My s...
successful history and stuff.
70.
April Fools Day Contest 2020: editorial _This was the most well-attended April Fools Day Contest in the whole history of them: 10343 participants solved at least one problem! It was also fairly well-balanced: while each problem has been solved by at least 200 participants, only 17 of them solved all 8 problems._
##[problem:1331A]
This was the consolation problem of the contest, and still a lot of participants asked me for hints on this problem — some even before the beginning of the round! If you're still not sure how to solve it, the contest announcement itself promised that the contest is not rated, so the answer is a resolute ``NO'' (case insensitive, quotes for clarity only) :-)
##[problem:1331B]
Unusually for this type of contests, the second problem had an actual problem statement! The real task was hidden in it using Steganography 101 — the first letters of the lines spelled out "TWO FACTORS".
[cut]
A quick look at the examples confirmed that you needed to factor the given number and print ...
_This was the most well-attended April Fools Day Contest in the whole history
of them: 10343
Tutorial of April Fools Day Contest 2020
71.
Multiple rating graph with other accounts We can view friend standings and we can view rating history graph for individual. Did you want to view rating history graph with friends? At least, I wanted.<br><br>Rating history graph on Codeforces uses flot jQuery plug-in and the plug-in support multiple data sequences. Therefore such functionality can be easily implemented. If many Codeforces users want, the functionality will be integrated by admin, hopefully.<br><br><p>So, I made <a href="http://yak2.myhome.cx/misc/multi_rating_graph_cf.user.js">user.js script</a> <b>(v1.3 2015/05/05)</b> to show usefulness of the functionality. The latest code is also at <a href="https://github.com/yak1ex/cf_userjs">github</a>. <b>[Updated: v0.02]</b> <u>Y-axis is adjusted when higher rating is shown, and message box appears when data can't be obtained properly.</u> <strong>[Updated: v0.03]</strong> <u>While you log-in, your rating graph appears in any profile page initially.</u> <strong>[Updated: v1.2]</strong> <u>Red dots for the hi...
Rating history graph on Codeforces uses flot jQuery plug-in and the plug-in
support multiple data, We can view friend standings and we can view rating history graph for
individual. Did you want to
72.
What is the story behind your username? I've just discovered this question on Quora: [What is the story behind your username at CodeForces?](https://www.quora.com/What-is-the-story-behind-your-username-at-CodeForces). I guess it'd be pretty interesting to hear stories from top participants. For instance, my handle's history is already described there.
This blog is dedicated to everyone who don't have Quora account, so you can share your histories and comments here.
I personally would love to hear stories from [user:tourist,2015-05-21], [user:rng_58,2015-05-21] and [user:WJMZBMR,2015-05-21] from current top-10.
pretty interesting to hear stories from top participants. For instance, my
handle'shistory is already
73.
CROC 2016: Programming Championship Hello, Codeforces!
<img src="http://assets.codeforces.com/images/croc-eng-logo-200.png" style="float: left;margin: 0 1.5em;max-width: 100.0%;max-height: 100.0%;">
In the spring 2016 the company CROC together with Codeforces will hold the third Russian Open programming championship «CROC – 2016». The goal of this project, as before, — encourage of the most talented and innovative young specialists and stimulate interest to the information technology.
As usual CROC company pays great attention to social projects, associated with the development of the IT-industry, to promotion of IT-professions and to the increasing interest in modern technology. CROC has rich experience of cooperation with universities, the organization of courses, seminars and competitions for pupils, students and experienced professionals.
The registration to the championship will be open from March, 1st to March, 16.
Anyone, regardless of nationality, place of residence and level of education, c...
## The history of the CROC championships
74.
DO NOT READ THIS POST IN THE EU !!!!HIGHLY ILLEGALL!!!! **DISCLAIMER: DO NOT READ THIS POST IF YOU ARE IN PORTUGAL FOR WORLD FINALS OR LIVE IN THE EUROPEAN UNION**
Attention World Finalists:
==========================
As you may know, Article 13 has been voted on by the European Union and all memes are now illegal. It is imperative that when you travel to Portugal you must LEAVE YOUR MEMES AT HOME, or they will be deleted at airport security and you will be arrested.
The contents of this post must be viewed at your own risk.
<spoiler summary="European-SFW mode:">
...
</spoiler>
<spoiler summary="Normal mode:">
...It is March 32, 2, and I'm back with more expert algorithm analysis that the legendary grandmasters don't want you to see. I have to take extra discretion with this one, since the government of an entire continent decided to ban my means of passing information.
Ladies and gentlemen, I present to you:
The Log Trick 2
---------------
[I...
World Finals for the first time in history.
75.
doubleCompare in testlib.h After the last ARC, one participant pointed out that the result is WA when the error is precisely the same as $EPS$ ([submission](https://atcoder.jp/contests/arc122/submissions/23379548)).
For example, consider these two outputs: `331997010.50000000000000000000` (the jury output) and `331997342.4970105` (the user output).
Their relative error is exactly $10^{-6}$, so when $EPS=10^{-6}$, this should get AC.
However, with the current implementation of the doubleCompare function in testlib.h, the result is WA.
This is because perturbations in the line 429 (`return result + 1E-15 >= minv && result <= maxv + 1E-15;`) don't work when the values of result/minv/maxv are large.
We made a fix and sent [a pull request](https://github.com/MikeMirzayanov/testlib/pull/126).
If you believe you were affected by this in the last ARC, please let me know.
That being said, given the popularity of testlib.h and the fact that no one has ever raised this issue, I hope no one was affected by th...
this in the entire history of testlib.h.
76.
Programming contest book reviews There are several programming contest books, but what do they contain and how good are they? Of course, it is difficult to know before buying and reading them. In this blog post I review programming contest books that I have read.
Do you know other books or have different opinions?
***
- **Programming Challenges: The Programming Contest Training Manual**
- URL: [http://www.programming-challenges.com/](http://www.programming-challenges.com/)
- Authors: Steven Skiena & Miguel Revilla
- Year: 2003
- Price (Amazon): 56.67 USD (paperback)
This is a classic book about programming contests, written more than ten years ago.
The book contains 14 chapters that discuss topics such as data structures, combinatorics, dynamic programming, and computational geometry. Each chapter begins with an introduction to the topic, followed by a collection of programming tasks.
A lot has happened in the world of programming conte...
. Typically, an analysis begins with a history how the task was invented. After
this, different ways how to
77.
How to become red. 01. Can a gray one become red? The most popular question on Codeforces must be "How to become red".
I've just (February 2021) ran a script and discovered that the current number of Codeforces profiles is 323553.
Only 1622 profiles have in their history a rating more than 2400. [cut]
I should say, not as many reds as I expected. [My script on github.](https://github.com/NataIss/codeforces)
I hope you remember that a newcomer used to start with 1500 points. I selected users who fell down to the grey level but did not give up and later became red.
Let me introduce these 40 brave guys:
- [user:Aleks5d,2021-02-19] min 1195 max 2683
- [user:Ali.Kh,2021-02-19] min 1167 max 2600
- [user:Alpha_Q,2021-02-19] min 999 max 2452
- [user:Arpa,2021-02-19] min 1057 max 2679
- [user:Arthur,2021-02-19] min 1158 max 2592
- [user:Atreus,2021-02-19] min 1134 max 2729
- [user:Bench0310,2021-02-19] min 1158 max 2502
- [user:CTPAX,2021-02-19] min 1188 max 2416
- [user:Danylo99,2021-02-19] min 1195...
profiles have in their history a rating more than 2400. [cut]
78.
Changes in CodeChef Problemsetting Hello Codeforces!
For the last half a year I have been working on CodeChef and was proposing ideas on how to change the problemsetting practices (hopefully, for the best). For some time the changes were in brainstorming phase, but as of now many of them are implemented. Today we are ready to share the information with you. But first I would like to approach people who are going to close this blog without reading:
If you are not interested in CodeChef contests at all, I think you should change your mind. Monthly short contests (Cook-Off and Lunchtime) have interesting quality problems, on par with Codeforces in my opinion (not AtCoder level yet, but who are?). Long and Starters are more targeted to newbie participants, with more classical educational problems.
If you are interested in setting problems for regular contests, you might want to do it on CodeChef. Some reasons:
- You don't have to set the whole round, as we work on per problem basis.
- This may be especially...
time limits, and judges, statement history versions, copyable sample IO, etc),
and are working on, , bulk editing of time limits, and judges, statement history versions, copyable
sample IO, etc), and
79.
Pinely Round 1 (Div. 1 + Div. 2) <img align="right" alt="text" src="/predownloaded/1c/91/1c91ed031100f3338aa5f8ed58d0405adb9ff9d7.png" style="height: 500.0px;max-width: 100.0%;max-height: 100.0%;">
Hello, Codeforces!
Members of team EZEC are glad to invite you to participate in **[contest:1761]**, which will start on **[contest_time:1761]**. You will be given **7** problems, **one of which has a subtask**, and **2 hours and 30 minutes** to solve them. The round will be rated for everyone. It is greatly recommended to read all the problems.
There is at least one interactive problem, so please see the [guide of interactive problems](https://codeforces.com/blog/entry/45307) if you are unfamiliar with it.
We would also like to thank:
- Our red sun [user:orzdevinwang,2022-11-19], the youngest TOP10 coder in history, for illuminating our path.
- Our great emperor [user:antontrygubO_o,2022-11-19] for cooperating and coordinating with us to make this round happen. He saved the round by contributing his problem...
- Our red sun [user:orzdevinwang,2022-11-19], the youngest TOP10 coder in
history, for illuminating, history, for illuminating our path. - Our great emperor
[user:antontrygubO_o,2022-11-19] for
Announcement of Pinely Round 1 (Div. 1 + Div. 2)
80.
Codeforces Round #486 (Div. 3) Hello!
[contest:988] will start on [June 1 (Friday) at 14:35 (UTC)] (https://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=6&year=2018&hour=17&min=35&sec=0&p1=166). It will be the third Div.3 round in the history of Codeforces. You will be offered 6 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
[Remember] (/blog/entry/59228...
round in the history of Codeforces. You will be offered 6 problems with
expected difficulties to
81.
Checklist for OI Problems (WebApp) Hello Everyone,
I guess everyone who is preparing for OI already know about this [Checklist for OI Problems](https://codeforces.com/blog/entry/59422) prepared by [user:ko_osaga,2018-11-01]. I've been using this for quite a long time, and it is really helpful!
But since the checklist gets updated from time to time, I found it hard to migrate from the previous checklist to new checklist. So, I made the following web app for the same purpose! Now you don't need to worry about migrating, I can just add the problems to database and it'll update automatically!
Link: [OI Checklist](https://oichecklist.pythonanywhere.com)
Please find the features and changes to the main checklist bellow:
Features and Changes
------------------
1. First of all, now the checklist contains direct link to each problem, while the main checklist had link to some parent of the link. And clicking on a contest name will lead to the official "Task" page of that contest, which generally contains jud...
want to search your browser history and delete all entries of
oichecklist.herokuapp.com. Happy
82.
Show 'Unofficial, but participated in contest time' Standings Feature I'm glad that we now have each user's unofficial contests history. I want another thing similar to this: *Can we have such standings table for each contest, too?* Currently, there's an option called 'show unofficial', which includes virtual participants, and for some reason practice submissions as well which is not meaningful to be there at all.
I think participating in contest time and participating virtually are fundamentally different. We don't know what information virtual participants already got before starting virtual contest. Even if they didn't actually read the problems, they could have heard some concept or technique required for them — which would be considered as cheating if that was on contest time — but we don't consider them cheating for virtual participants, but they're treated the same as unofficial participants who solved them in contest time in unofficial standings table.
As someone who also hosted 3 rounds before, I like to look back at these roun...
. I assume it's not hard to implement it as we already have it in personal
history page, so I want to, I'm glad that we now have each user's unofficial contests history. I want
another thing similar to, history long ago, anyone knows why they're removed?
83.
Serious Altitude Issue in IOI 2025 Hello, CodeForces!
Today, I would like to discuss about an issue of IOI 2025 venue.
The venue of IOI 2025 is still not officially announced, but according to [the website](https://ioi2025.bo/), IOI 2025 will be held in La Paz, Bolivia.
<img src="https://i.ibb.co/PFjkSF1/1.png" alt="1" border="0" width="40%"></img>
As you know, La Paz is one of the highest cities in the world. For example, the center of La Paz is at 3600 meters above the sea level, and [El Alto International Airport](https://en.wikipedia.org/wiki/El_Alto_International_Airport), which is the nearest large airport from La Paz, is at 4100 meters above the sea level. Therefore, **altitude sickness can be a big concern.** I think that even the following things can happen:
* 20% of the contestants collapsed at the airport, and they were even unable to reach hotels
* 30% of the contestants collapsed during hotel stay, opening ceremony, practice sessions and excursions, and they were unable to participate in the c...
contest, and the biggest upset in IOI history occured If I were an IOI 2025
participant, I have, . Many LGMs, IGMs and GMs made blunders in the contest, and the biggest upset
in IOIhistory occured
84.
Polygon Updates (Fall-Winter 2014) <a href="https://polygon.codeforces.com/"><img src="https://polygon.codeforces.com/image/polygon-logo.PNG" style="float: left; margin: 1em 2em 1em 1em"/></a>
Hi Codeforces!
My name is Maxim Gusarov and I joined the Codeforces developer team in September and am recently working with Vitaly [user:kuviman,2014-12-24] Kudasov on improving the [Polygon](https://polygon.codeforces.com/) system.
Today I would like to introduce you to the new potential of the system where all problems for the Codeforces rounds and many other programming contests are prepared.
#### Update 1
As a user logs into the system, she can now use either the login or the email given at the registration. You can also attach the session to the IP address to enhance security.
<center>
<img src="http://assets.codeforces.com/images/polygon-post/login-by-email-and-attach-to-ip.png"/>
</center>
#### Update 2
Any user who has the access to edit a problem can become its supervisor. The supervisor will always...
revision of the problem you need together with the editing history if you
switch on it beforehand.
85.
Ten Years of Competitive Programming 4 Hey, Codeforces!
I’m AmirReza PourAkhavan, the former Codeforces Contest Coordinator. I let the story become complete and I’m sharing it now.
The story is about a 16-year competitive programmer, who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals, twice.
Read the previous parts: [1](https://codeforces.com/blog/entry/107465), [2](https://codeforces.com/blog/entry/108838), [3](https://codeforces.com/blog/entry/114356).
**Read the Persian version** [**here**](https://docs.google.com/document/d/e/2PACX-1vSUoFC9tLgDCji6rSCYy-RYoUG1_6uOQnHz_LlLKe6KksWBYWO4r6clDly5YxIgzu1g3Tj31weDxgWz/pub).
What happened previously
===
I was a lone programmer, in a small city, trying to learn CP and prepare for the Iran National Olympiad. It was not as successful as I expected. I tried to change my school and I immigrated to Tehran, alone. I entered AE high s...
history, and it happened on the day of our contest. I saw this as a misfortune
and added it to the
86.
Introducing Discode: platform for live code collaboration with voice rooms Hello CF,
**Update:**
Just after releasing it I got busy and stopped working on it, but recently have made some changes:
- Rooms are now using 128-but UUIDs, so no actual chances that anyone can invade ur room without your knowledge. Your previous rooms will still be usable tho
- Large Code, Input and Output are supported now
- Font Size is editable now
- When a user joins a room, syncing is fixed
- Live code sharing has been improved and now multiple people can write on different lines, but very fast typing and typing on same line can still cause issues :catThink:
- Deployment procedure is also very easy now, so any changes in future will be refelected very soon in the actual website
So Yeah, in end it is much more usable alone than it is with many people in same room. Anyways, that's the update.
-------------------------------
So recently I've been working on a little project which I think might be useful in CP as well, so this blog is to showcase i...
Your room history, theme, and language choice are stored for a better
experience, but it's on the
87.
Team history The teams feature on codeforces let you join team and practice in training together. It is a wonderful system that provide options and encourage cooperation. However, the team history feature that come along with it can be a bit problematic.
If you haven't noticed, once you leave a team by either getting kicked or just leaving it yourself, the team will show up on your teams page under history. This will be shown for everyone, so it's available even if you're not logged in. As far as I know, there is currently no way to hide this.
This can be problematic because if you agree to join a team and then was kicked, whoever is left in the team can essentially write anything they want on a part of your profile. This can be something benign like simple jokes/memes, something more problematic like opinions no one should hold, or straight up just doxxing by writing your real name or some kind of unique identifier.
Further more, sometime people just want to forget. Imagine dating someone...
Team history, hide teams / teams history will do. If the developer are feeling generous,
maybe we can even have, proposal and the teams history feature in general., wonderful system that provide options and encourage cooperation. However, the
teamhistory feature that, , the team will show up on your teams page under history. This will be shown
for everyone, so it's
88.
Codeforces Round #100 <p>Hello everybody!</p><p>I hope you have finished New Year celebrations, or you are ready to make a small break to take part in the anniversary Codeforces Round #100. Round will have place <a href="http://timeanddate.com/worldclock/fixedtime.html?day=4&month=1&year=2012&hour=19&min=0&sec=0&p1=166" style="color: rgb(0,0,204);font-family: verdana , arial , sans-serif;font-size: 12.0px;line-height: 20.0px;background-color: rgb(255,255,255);">January 4 at 15:00 (UTC)</a>. There will be a common contest for participants of the both divisions with the same set of 6 problems. The top 100 participants of the contest receive <a href="http://codeforces.com/blog/entry/3461?locale=en">prize t-shirts</a>.</p><p>Score distribution: <b>500-1000-1500-2000-2500-3000</b> <br /></p><div>As you may have guessed, the author of the problems is me. Invaluable help in preparation (and a bit in inventing) of problems was provided by Artem Rakhov <span style="font-family: verdana , arial...
round in Codeforces history! Much to our surprise, the 100th place was shared
by two contestants:
Announcement of Codeforces Round 100
89.
Open sourcing KTH's Team Reference Document We just made KTH's ICPC team reference document [open source](https://github.com/kth-competitive-programming/kactl).
It contains a few nice things that I haven't seen elsewhere:
- Ergonomic API's for [SCC](https://github.com/kth-competitive-programming/kactl/blob/master/content/graph/SCC.h), [biconnected components](https://github.com/kth-competitive-programming/kactl/blob/master/content/graph/BiconnectedComponents.h), [2-SAT](https://github.com/kth-competitive-programming/kactl/blob/master/content/graph/2sat.h), [angle sweepings](https://github.com/kth-competitive-programming/kactl/blob/master/content/geometry/Angle.h), and [monotone function partitioning](https://github.com/kth-competitive-programming/kactl/blob/master/content/various/ConstantIntervals.h).
- I don't recall seeing [tridiagonal linear equation solving](https://github.com/kth-competitive-programming/kactl/blob/master/content/numerical/Tridiagonal.h) or [tree compression](https://github.com/kth-competitive-programmi...
/kth-competitive-programming/tinykactl/), with version control history going
back to 2002. (Did you, history going back to 2002. (Did you know that in 2003, the ICPC did not have a
page limit for
90.
[Gym Contest] ACM Egyptian Collegiate Programming Contest (ECPC 2017) online mirror Hello CodeForces! I'd like to invite you to the online mirror of the 2017 ACM egyptian collegiate programming contest ,which will be held on Wednessday, [6 July 2018, 02:00pm Cairo time](https://www.timeanddate.com/worldclock/fixedtime.html?msg=ACM+ECPC+2017+online+mirror&iso=20180706T12&p1=1440&ah=5)
contest link: [ACM ECPC 2017](https://codeforces.com/gym/101840)
standings: [link](https://icpc.baylor.edu/regionals/finder/ecpc-2017/standings)
ACM ECPC 2017 Highlights: <iframe width="800" height="480" src="https://www.youtube.com/embed/SnWAD7chUQA" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
the problems were prepared and tested by :
[user:Thrax,2018-07-03] -chief judge-,[user:Badry,2018-07-03], [user:Noureldin,2018-07-03], [user:SyrianPetr,2018-07-03], [user:safrout,2018-07-03], [user:Lvitsa,2018-07-03], [user:amrSamir,2018-07-03], [user:Amirnasr,2018-07-03], [user:islam-al-aarag,2018-07-03], [user:justHusam,2018-07-03] and [user:RedStone,2...
of 'codeforces history' so I can't modify it, so I created another one with
the original tests used, now the contest is part of 'codeforces history' so I can't modify it, so I
created another one with
91.
Teams Going to the 2024 ICPC North America Championship The list of teams qualified for the [2024 North America Championship](https://nac.icpc.global/) has been [posted here.](https://icpc.global/regionals/finder/North-America-Championship-2024/teams)
So far, there are 48 teams there. I expect that 2 more will qualify and will update this post when they do.
Please comment the codeforces handles of your university's team if you know them, and I'll add them to the list. :)
Edit: There are now 50 teams. I expect that there won't be any more.
[East Central North America](https://naeast23.kattis.com/contests/naeast23/standings?filter=5332)
==================
| University | Member 1 | Member 2 | Member 3 |
|-------------------------------|----------|----------|----------|
| University of Waterloo | [user:KevinWan,2024-03-01] | [user:uwu,2024-03-01] |[user:pwypeanut,2024-03-01] |
| University of Michigan | [user:docriz,2024-04-21] | [user:wbyyui,2024-04-21] | [u...
[Southern California](http://socalcontest.org/history
/2023/SCICPC-2023-2024-PreliminaryResults.html
92.
About the word "Editorial" I'm not a native English speaker, so I mostly learn English by books or internet. When I [look up Collins English Dictionary](https://www.collinsdictionary.com/dictionary/english/editorial) about the meaning of "Editorial" :
"An editorial is an article in a newspaper which gives the opinion of the editor or owner on a topic or item of news."
That's something we call as "사설" in Korean. In Korea, people write editorial about our recent president impeachment, thoughts on foreign policies, or the Chinese food restaurant nearby their office. If someone uses that phrase to describe solutions, it will be really awkward.
In Codeforces, when we say "Editorial" it mostly means "Solution" — that is, mathematical facts. So, according to dictionary, this post is more likely to be called as "Editorial" than the usual one we know.
Then, why does CP community uses the word "Editorial" for referring solution? Does it have some other meaning related to "solution"? If not, is there some...
other meaning related to "solution"? If not, is there some history for using
that phrase?, some history for using that phrase?
93.
38th Petrozavodsk Programming Camp. Results. <img align="right" width="30%" height="30%" src="/predownloaded/59/cb/59cb1300ebd30c6465012e4f77f8ccde33e2281d.jpg">
From 28.01.20 to 07.02.20, Petrozavodsk State University held 38th Petrozavodsk Programming Camp.
47 teams participated in the competition from 33 universities, 25 cities, 11 countries (Russia, Belarus, Kazakhstan, Poland, Romania, Latvia, Ukraine, South Korea, China, USA, Japan)
Petrozavodsk Programming Camp is traditionally a training platform for International Collegiate Programming Contest (ICPC) winning teams: over the past 18 years, 13 times the camp participants became winners in ICPC World Finals. This time from 47 of participating teams 18 teams will take part in ICPC World Finals 2020.
Petrozavodsk Programming Camp consists of nine days of contests and two <s>upsolving days</s> days off between them.
One of the camp's features is that participants and sponsors are generally the authors of contests. This time the authors were: [user:300iq,2020-02-13];...
The camp have been held for a long time and have its own history. During the
current one, we
94.
[Tutorial] The sparse set data structure <big><big>Hello, Codeforces!</big></big>
I recently came across a data structure that I find quite interesting: the **sparse set**. It functions similarly to a bitset and supports all its operations but has some quirks and useful features of its own. Particularly, unlike almost every other data structure, it does not need to be *initialised* at all before it can be used! Naturally, that also means that its data can be reset in $O(1)$ time, as opposed to the $O(n)$ time expected of regular bitsets. It also has the added benefit that traversing its elements takes time proportional to the number of elements rather than the size of the data structure, making the operation more efficient for sparse bitsets. However, note that it is likely less efficient in terms of its memory usage (still $O(n)$ but ~64× larger constant) and constant time factor.
## Introduction
The sparse set consists simply of two integer arrays (which I'll call $d$ and $s$) and a size variable $n$, satisfying th...
](https://research.swtch.com/sparse), which provides some interesting history
and a great summary of
95.
Google Code Jam Archive <img src="/predownloaded/7f/8d/7f8d55b1b894353c4dff1090934435ce67afc0b5.png" style="float: right; width: 274px"/>
Hi everyone,
As most of you already know, Google has discontinued their Code Jam and Kick Start competitions, and plans to completely shut down its competitions website on July 1st 2023.
It would be a shame if all of its 20-year history just vanishes, so I decided to download, more or less, the whole competitions website.
All of the 205 scoreboards, 716 problems, editorials, test data, and all of submitted code (3547830 total files) where it's still available.
The archive is published here:
https://zibada.guru/gcj/
I added some problem statistics (fastest/shortest solutions), Codeforces handles, and dark mode :)
This is a pure static HTML website, which you can download entirely and keep a local copy, the archives are 3 GB in total.
In case you prefer problem statements in PDF, printing-to-PDF from browser gives surprisingly decent results.
<s>For now,...
2023. It would be a shame if all of its 20-year history just vanishes, so I
decided to download, all of its 20-year history just vanishes, so I decided to download, more or
less, the whole
96.
Tips on debugging "WA on pretest 2"? Hey all,
I find one of my biggest weaknesses is debugging efficiently under contest settings. If you look at my contest history, there are plenty of instances where I get horrible penalties and wrong multiple submissions on a given problem before potentially solving it. The most recent example is today's Educational Round, where I took 40 minutes to figure out what was wrong with my D solution.
I am well aware that there are plenty of blogs and posts on debugging upon Googling, but a lot of the advice is kind of generic and don't always work for me, so I was hoping to get some more specific answers via this blog.
I'll try to provide some context so you know what I'm already doing. **Here is my current debug strategy during contests:**
**TLE/MLE/RE**: Usually not very common for me. I just look for common sources of these errors. For TLE or MLE, I check things like allocating lots of vectors inside loops, while loop conditions and recursive functions, etc. For RE, I check fo...
my contest history, there are plenty of instances where I get horrible
penalties and wrong multiple
97.
Team preview: Moscow State University 
This year my alma mater is represented by team Moscow SU Tapirs.
Moscow State University has a long history at World Finals. 19 appearences, 4 Gold medals (all of them — 2nd places), 1 Silver and 7 Bronzes. Moscow SU is also 2 times champions of Europe.
Tapirs team came 2nd last year in Yekaterinburg in intense battle with St. Petersburg State University. In NEERC 2014 they came second as well, while losing to ITMO University team only on penalty time. Moscow SU is currently 3rd in OpenCup standings with one stage win. They had bested ITMO team on 2 more stages. Anton Pankratiev is team coach.
Gleb Evstropov (TC: 2405, CF: [user:GlebsHP,2015-05-18] 2622) got 3rd in this year Facebook Hacker Cup. He also won Silver medal in IOI 2010 and was Russian Code Cup finalist last year.
Victor Omelyanenko (TC: 2531, CF: [user:TeaPot,2015-05-18] 2687) got 2nd place on...
University has a long history at World Finals. 19 appearences, 4 Gold medals
(all of them — 2nd, Moscow State University has a long history at World Finals. 19 appearences, 4
Gold medals (all of
98.
A Well-known Data Structure -- Version Tree ## Back Ground
I managed to solve [CF707D](https://codeforces.ml/contest/707/problem/D) and at that time I didn't know this trick. After thinking for a while, I had a really good idea about solving it. After I read the tutorial I saw that this solution is mentioned in Solution No.1. But I really learned I good way of solving data structure problems including the following operations.
$1.$ Modify based on version x and the result is assigned version x
$2.$ return ... in a state they were after applying $k$-th operation.
For these questions, we could build a tree and solve the queries by **DFS** if off-line solutions are allowed.
## Construction
The construction is quite easy. If version $v$ is modified based on version $x$, we add an edge from version $x$ to version $v$.
Because every version only has exact one father so obviously, the graph formed a tree.
## Query
The answer of a query is affected by the modifications on the path from the root to this version...
every history version. Use $lat[x]$ to record the index of the latest version
of array $x$.
99.
Codeforces Contest Rules This is a detailed and formal version of the Codeforces contest rules. If you just want to learn the rules, we recommend
that you first read the post [Codeforces Contests](http://codeforces.com/blog/entry/456).
The organizers may slightly modify the rules for specific rounds, then this information is contained in the announcement of
the round. The following rules should be regarded as default rules.
### General information about a round
1. You need to register to participate in a round. The registration opens six hours before the start of the contest and closes 5 minutes before it, unless the information about the round states otherwise.
1. The system of conducting contests has two interface languages available: Russian and English. The contestants can switch between these two languages.
1. A round continues for 2 hours, unless the information about the round states other duration time.
1. Contestants are given 5 problems to solve, unless the information about the ...
history of submissions of each contestant.
100.
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...
participation, submissions and contest history).
101.
[Competitive_Programming] A new tool for competitive programmers بسم الله الرحمن الرحيم
**Hello**, I would like to introduce The **Competitive Programming** tool. It provides several useful features for competitive programming.
### **Test your code for testCases:**
You can test your code for several test cases at the same time and you can load the test cases supplied in the problem automatically just by pasting the link of the problem in the tool and let it load the test cases for you (This work for Codeforces, Atcoder)
<a href="https://ibb.co/qd164bw"><img src="https://i.ibb.co/mGzpYQ7/Screenshot-from-2021-09-26-17-44-45.png" alt="Screenshot-from-2021-09-26-17-44-45" border="0"></a>
### **Submit your solution:**
This tool can also submit your solution automatically to your account from the tool itself and load the results of your submission (Accepted, Wrong answer, ..etc)
(This work for [codeforces.com](codeforces.com) and [atcoder.jp](atcoder.jp))
<a href="https://ibb.co/C6sXBcb"><img src="https://i.ibb.co/W0pdnhk/Screenshot-fr...
#### **History of updates** You will need to re-download the program for the
latest update because
102.
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...
I want to start from some history and remember that the tradition to publish
travel notes about
103.
Team preview: The University of Tokyo 
Today let’s talk about The University of Tokyo team !#$%&()*+-./:;<=>?@[\]^_`{|}~.
University of Tokyo has long history of World Finals participations, this would be 13th time. They won one Gold, one Silver and 2 Bronzes, and 2 members of this year team won Gold in 2013.
They won regional contests in Tokyo and Kuala Lumpur, only team in Asia this year with such achievement. Team is currently on 17th place in OpenCup standings, although they skipped several stages and not always had optimal line-up. Tomoyuki Kaneko coaching them.
Kensuke Imanishi (TC: 2625, CF: [user:wrong,2015-05-17] 2298) won 2 Silver medals in IOI (2010 and 2011) and was GCJ Finalist in 2013, that's beside his Gold in ACM ICPC Finals.
Shogo Murai (TC: 3017, CF: [user:semiexp,2015-05-17] 2507) has 3 IOI Golds (2010-2012) and target on TopCoder to boot.
Makoto Soejima (TC: 3468, CF: [user:rng_5...
!#$%&()*+-./:;<=>?@[\]^_`{|}~. University of Tokyo has long history of World
Finals participations, this would be 13th time. They, Tokyo has long history of World Finals participations, this would be 13th
time. They won one Gold
104.
Codeforces Top 100 Comments Hi guys, Here you can find Top 100 Comments in the history of Codeforces Til 1 Jan 2015. It reminds us of some memories we had together in Codeforces :)
### Top 100
[user:yeputons,2015-01-01] 448 http://codeforces.com/blog/entry/8063#comment-138056
[user:zeulb,2015-01-01] 438 http://codeforces.com/blog/entry/10193#comment-156433
[user:Petr,2015-01-01] 354 http://codeforces.com/blog/entry/12605#comment-174158
[user:zakharvoit,2015-01-01] 326 http://codeforces.com/blog/entry/12605#comment-174167
[user:ashmelev,2015-01-01] 318 http://codeforces.com/blog/entry/4302#comment-87389
[user:tourist,2015-01-01] 307 http://codeforces.com/blog/entry/7499#comment-133421
[user:MikeMirzayanov,2015-01-01] 305 http://codeforces.com/blog/entry/1767#comment-33686
[user:Gogis,2015-01-01] 297 http://codeforces.com/blog/entry/15511#comment-204474
[user:sorry_dreamoon,2015-01-01] 287 http://codeforces.com/blog/entry/15336#comment-202752
[user:MikeMirzayanov,2015-01-01] 286 h...
Hi guys, Here you can find Top 100 Comments in the history of Codeforces Til 1
Jan 2015. It reminds
105.
List of All Open Cup Contests Open Cup has very high quality problems. I made a list for all the contests containing the standings, sources, upsolving links, statements and discuss blog in codeforces. Some materials and links of old opencup contests are missing, maybe [user:snarknews,2020-11-10] could help to fill these entries.
I will update the list when new opencup stages published.
Note: most of the upsolving links need the logins for yandex.contest or opentrains.
## XXI Open Cup named after E.V. Pankratiev
| # | Contest | Upsolving | Materials |
|:--:|:------------|:--:|:--:|
| Stage 1 | [Grand Prix of Eurasia](https://official.contest.yandex.ru/opencupXXI/contest/20063/standings)<br/> [XXI All-Siberian Programming Contest. Online](https://olympic.nsu.ru/files/inet_res_2020_0.pdf) | [baekjoon](https://www.acmicpc.net/category/detail/2403)<br/> [yandex](http://official.contest.yandex.ru/opencupXXI/contest/20063) | [statement](https://yadi.sk/i/dsRvTxbgJ9fDXw) [discuss](https://codeforces.com/blog/...
ICPC North America Championship](https://nac.icpc.global/history
/2020/scoreboard/) | [kattis](https
106.
Just a random clip from ICPC Luxor World Finals Award Ceremony I was waiting for somebody to post this, but I guess I am going to post it for history purposes. Here is the clip:
[https://youtube.com/clip/UgkxjClduTG6kL6s3c8BFNNYdE1HVR2wGMxf?si=pFZCy3KapKbTLNCC](https://youtube.com/clip/UgkxjClduTG6kL6s3c8BFNNYdE1HVR2wGMxf?si=pFZCy3KapKbTLNCC)
They cut it out pretty quickly in the broadcast, but let me tell you what we were seeing from the audience. The team of KNU is coming to the stage. They all have some kinds of pins on their T-shirts with Ukrainian flags. In the clip, you can see it if you pause and look closely. But they switch the camera away quickly. Then the team members and the coach go behind the big screens. Normally other teams go out on the stage pretty quickly, but here nothing is happening for like a minute. Then they walk onto the stage, with no pins anymore. I don't know what happened behind these screens, but it probably isn't hard to make an educated guess. For context: [clip from EUC](https://youtube.com/clip/UgkxDroRHQ8d...
I was waiting for somebody to post this, but I guess I am going to post it for
history purposes
107.
Barcelona Bootcamp — Teams and Sponsorship update <img src="/predownloaded/a6/1b/a61be4b7ba01cf0feb68d6e5e00eb9d467fe8519.png" style="float:right;">
For the last 6 years the world titles have been won only by St Petersburg teams – ITMO and St. Petersburg State University – both universities will bring their top teams to [2nd Hello Barcelona Programming Bootcamp in collaboration with Moscow Workshops ACM ICPC](http://in.harbour.space/icpc/acm-icpc-hello-barcelona-bootcamp-autumn-2017/?utm_source=Codeforces)
The event runs from Sept 27 to Oct 5 – but how to get the most out of the camp?
"I think there is no universal solution for "get the most out of a camp" – everyone should find their own path, but the general guideline will be: communicate with other participants as much as you can, make sure you do upsolving (at least some), keep track of how much you sleep," said [Gleb Evstropov](https://goo.gl/srpKTu), coach and coordinator of the programming committee.
Sleeping could be somewhat challenging with all the famous Russian ...
investment bank of Eastern Europe and Russia, with over 170 years of history.
Thanks to their support we
108.
Teams Going to the 2023 ICPC North America Championship Most North America ICPC regionals have been held. While we don't yet know who is going to NAC, it's reasonable to guess that the slot distribution will be similar to last year. So here is a list of teams who qualified for NAC assuming the same distribution. Note that all regions are guaranteed at least 3 slots, and I would be relatively surprised if any region received less than 4.
Update: It looks like an official list has been [posted here](https://icpc.global/regionals/finder/North-America-Championship-2022/teams). I've updated the tables below in accordance, with the exception of Pacific Northwest, which has some irregularities.
Update 2: UC Davis now appears on the list, so everything seems normal now. 48 total teams invited.
Update 3: Stony Brook University and Northeastern University have been added to the list, for a total of 50 teams. I expect there will be no more additions beyond this.
If you know the codeforces handles of any team that is not yet filled in, ple...
[Southern California](http://socalcontest.org/history
/2022/SC2022-2023-PreliminaryResults.html
109.
codeforces IRC channel IRC?? What's that? --> See the bottom of this blog.
There have been some discussion about a codeforces chat [here.](/blog/entry/82#comment-218753)
I have created channel **#codeforces** at network **IRCNet**, welcome!
Rules:
1. Do not talk about problems during contests.
2. Use common sense.
There should be some channel operators (who are like moderators). However, not everybody can be a operator because the risk that someone does something stupid is too high.
To become a channel operator you have to:
1. Have done at least 15 contests at codeforces
2. Have max rating >= 2200
3. Have a decent contribution on codeforces.com or chat history on #codeforces
Please comment if you have some suggestions. **Especially I would like to hear what you think about the conditions to become a channel operator.**
#### Have never heard about IRC?
IRC is short for Internet Relay Chat, a very handy instant messaging protocol. The IRC consists of different networks and...
3. Have a decent contribution on codeforces.com or chat history on #codeforces
110.
NEF & ROHSTPC Hello friends!
<img src="/predownloaded/36/a8/36a8f8392e9ed1ea75715400c943949f8ad4c6dc.png" align="right" style="height: 235px; margin: 10px;" alt="text"/>
<a href="https://youtu.be/ZuzBPpBy-sE" style="font-size: 15.0px;padding: 8.0px 14.0px;background-color: rgb(100, 65, 165);color: white;">ICPCLive broadcast</a>
<a href="http://nerc.itmo.ru/archive/2019/standings.html" style="font-size: 15.0px;padding: 8.0px 14.0px;background-color: rgb(55, 109, 171);color: white;">Standings</a>
<a href="http://nerc.itmo.ru/archive/2019/nerc-2019-statement.pdf" style="font-size: 15.0px;padding: 8.0px 14.0px;background-color: rgb(55, 109, 171);color: white;">Problems</a>
This weekend we'll hold two large-scale final stages of important Championships in the region: ICPC Northern Eurasia Finals 2019 and Russia Open High School Team Programming Contest.
Competitions are traditionally held at several places: in St. Petersburg, Barnaul, Almaty, Tbilisi and Kremenchuk. School tea...
competition. 128 of them will meet in Saint Petersburg in the historical park
"Russia — is myhistory". 49
111.
[Setup] On using vim, make and gdb for online (CF, AtCoder) and onsite (ICPC, IOI) contests Since [someone recently asked me](https://codeforces.com/blog/entry/108613?#comment-985873) about my competitive programming setup, and I like tinkering with my setup to make it as useful and minimal as possible, I thought I should share my setup that I've used for the past few years and a modified version that I've used at onsite ICPC contests. I've also talked to a few people who went to IOI and had a similar setup, and I'm fairly confident that at least some people will be able to successfully use this without having to worry too much about the details, like I did. This is definitely NOT the only way to set up a basic environment, but it was the way that worked for me for quite a long time.
This blog is also meant as a companion blog to [this blog on using the command line](https://codeforces.com/blog/entry/102287).
Before we start with the tools, it's a good point to mention [this resource](https://github.com/ancc-iitd/competitive-programming-resources/tree/main/setup) as ano...
=popup sw=4 ts=4`: does the following things in order: sets history to 500
lines, makes the numbering, set noshowcmd noruler set history=500 set autoread set so=7 set wildmenu set
wildignore=*.o
112.
Codeforces::Gym <p> We've made it! Or in any case, we are at least very close to it. </p> <p> On January 19, 2012 at 12:00 we open a sub-project called "Gym". In short, its goal is to enable the Codeforces coders not only to participate in competitions and discuss them, but also to train and coach easily. </p> <p> In fact, despite the wide diversity of online judges in the world, a well thought-out training service system does not exist. So, the expectations from this system are: </p> <ol> <li>Collection of online contests, composed mainly of the past official contests. </li><li> Opportunity to integrate the final standings of past contests in the online contests to be able to train "against" the official participants. </li><li> Opportunity to participate in the training at any time whatsoever, without fear that something breaks down and the server will fall. In short, reliability. </li><li> Opportunity to write virtual contests and to solve the problems in a practice mode. </li...
statistics and participation history, the possibility to compile and publish
reports on selected
113.
10 Reasons to Prepare Problems in Polygon <img src="http://assets.codeforces.com/images/poly21.jpg" style="float:right;margin:0 0.5em 1em 1em;"/>
Hello Codeforces.
Just a reminder about something most of you know. Polygon is a service to prepares programming problems and contests.
It is usually used to prepare problems for olympiads/programming contests but it is also often used to prepare
educational content. It is located at https://polygon.codeforces.com/ and is open to everybody.
I have recently found out that it's been more than five years since the creation of Polygon. It's high time to summarize
the experience we've accumulated.
I first publicly spoke about Polygon in a narrow circle of Russian teams' coaches on ACM-ICPC World Finals in 2009. I
cannot say that everybody was enthusiastic about the innovation. Some people were openly skeptical about such system's
viability and relevance. After 5 years on the ACM-ICPC finals in Ekaterinburg Oleg Hhristenko ([user:snarknews,2014-11-03]) said
that in his o...
editing history, developing access, automated invocations and other things.
114.
Plan to go from expert to master in 3 months A couple days ago a most dearest friend told me to participate in his cf round, this instantly reminded me about my embarrassing blog history where I made a plan to get to candidate master and bailed quickly after.
To right this wrong, I come before you today with a more ambitious plan, which is making master in 3 months.
If you have read up to this point, that means you are at least mildly interested in this grandiose journey, and so you probably have a few questions. Fear not, I have prepared a list of FAQ for your convenience.
### **FAQ**
- Why?
Solving problems is pretty fun, however, having your name stained with a boring blue is not. This journey is aesthetically motivated.
- How?
Last time my plan was not very simple and choosing the problems was time consuming, I think that contributed to its failure. Furthermore, I don't think master is an unreasonable goal (as in, I believe anyone can get it given enough practice). Therefore, in the interest of succ...
reminded me about my embarrassing blog history where I made a plan to get to
candidate master and bailed
115.
Bayan 2015: History This year is 3rd edition of Bayan Contest.
Inaugural contest took place in 2011. About 800 university and high school students from all Iran tried to qualify for the finals through 2 online rounds and best 30 of them participated in the finals at Bayan offices in Tehran. Seyed Hamed Valizadeh won university stundents contest while Saeed Ilchi won high school part.
 
Next time Bayan decided to hold international contest. Codeforces was used to select international participants while Bayan's own system was used for selecting Iranian finalists as well as for the final itself. This time 1286 participants from 54 countries and 1728 from Iran tried to qualify and 8 international and 16 local finalists arrived to Parsian Azadi Hotel on February 16th 2013 in order to decide who is the best. [user:0O0o00OO0Oo0o0Oo,2015-04-30] won the contest, [user:cerealguy,2015-04...
Bayan 2015: History
116.
Codeforces Marathon Round 1 — discussion The Codeforces Marathon Round 1 is over
([results comment](/blog/entry/45592?#comment-301795)).
As the final solutions are being tested,
I think many participants will want to share ideas
and learn alternative approaches.
I'll start with the ideas I tried myself, both successful and not;
as I've seen in the submissions,
the contestants have more ideas, but I hope they will share themselves.
For each of the solutions below, the numbers in square brackets are
minimum, mean and maximum score when running on 1000 tests locally.
I have to note in advance that the constants and technicalities
in the solutions are not considered optimal: the score just shows
approximate relation between ideas and may often be improved a bit.
[cut]
-----
###### **Solution 1** [`4099 4159.699 4288`]: random.
Just print 5000 random bits 100 times.
###### **Solution 2** [`4160 4226.294 4365`]: last bit memorization.
The last checked bit is always wrong.
For example, if the answer fo...
A bit of problem history. Initially, it was designed as a hard probabilistic
problem for a
Discussion of Codeforces Marathon Round 1
117.
Predict: orzdevinwang will reach 4000 in 1 year. As we have witnessed, in the recently concluded [CodeTON Round 6](https://codeforces.com/contest/1870), [user:orzdevinwang,2023-09-19] achieved [the 1st place](https://codeforces.com/contest/1870/standings/participant/163890042).
In fact it was the second time that he got rank#1 in Div.1+2: [rank#1](https://codeforces.com/contest/1782/standings/participant/147801267) in the [Codeforces Round 844](https://codeforces.com/contest/1782).
This is only what he has achieved on Codeforces; when we examine his achievements in other areas, we can still be surprised.
For example, on the AtCoder, he has been rank#1 in AGC for 3 times yet.
- [AGC060](https://atcoder.jp/contests/agc060/standings)
- [AGC062](https://atcoder.jp/contests/agc062/standings)
- [AGC063](https://atcoder.jp/contests/agc063/standings)
And the 4th place in [AGC061](https://atcoder.jp/contests/agc061/standings); and rank...
He has been the youngest LGM in the history of Codeforces so far. (I mean the
age when he reached
118.
[Archive] My Father is Ratist **UPD 26/10/2023**: I find this blog very funny and a very relatable pasta for some of us, so rather than archiving it, I'll just post this. By the way, please to all the people out there. Don't feel like practicing CP a burden. It's something you should enjoy, and if you don't please quit. My relationship with my father doesn't get any better since I've posted this two years ago. But at least now that I'm turning 21 makes my brain a bit more considerate to people.
---
Hi everyone. Competitive programming is an entertaining activity. I love it, and it really helps me even in my daily university courses I had. I've been doing CP for 5 years (well, I had breaks in between and other stuff to do and study besides doing cp).
This post is not a rant or a "hello sir, can you help me improve in cp"-type of post. I just wanna share some story that makes me sad. But don't feel pity for me and say I'm a crybaby and I should get good. I'm in catch with my goal and trying my best.
I don...
, he knows my cf handle, and I think constantly checking on my account and/or
contesthistory. Until
119.
Preview: University of Tokyo Next team is Tokyo University team called “University of Agitsune”. Its name has an interesting history. The team members name themselves like 3 animals — rabbit (usagi in Japanese), eel (unagi) and fox (kitsune). If you combine a rabbit and a fox, you will get usagitsune. If you combine an eel and a fox, you will get unagitsune. Replacing by dash letters that differ, we can obtain u-agitsune. And as University of Tokyo is sometimes referred to as U-Tokyo, reversing the rule, we get the team name (credit for this explanation should go to ~qnighy,2013-06-26).
Last year 2 of its members participated in OpenCup under name “Kroliki” (transliteration of Russian word for rabbits). This is not a coincidence, as Makoto Soejima learns Russian. They finished 7th in general classification with one second and one third places on stages.
This team finished first in Tokyo Regional Contest, one problem ahead of second place, and third in Kaohsiung Regional Contest. They also finished firs...
history. The team members name themselves like 3 animals — rabbit (usagi in
Japanese), eel (unagi
120.
Introduction <div style="float: left;margin: 1.0em;font-size: 11.0px;text-align: center;"><br><img alt="The team captain Natalia Bondarenko" src="http://lh5.ggpht.com/_mSdPzSw5zAo/S2bNbN16BJI/AAAAAAAADIc/bz6GQyvSLpQ/natasha.jpg" title="The team captain Natalia Bondarenko">
<br> The team captain Natalia Bondarenko </div>
January 30, 2010 the delegation of the Saratov State University is
leaving for the World Finals of the International Collegiate Programming
Contest. This year it's held in Harbin (hi, China), and that means that
apart from an interesting contest, we have cold weather, ice statues,
fried rice with prawns, and as I hope, Beijing Duck. <p> Our
University will take part in the Contest for the 7th time, and for the
team Saratov SU#1 this will be the 2nd Finals. It seems to be high
time to introduce myself. I'm Mike Mirzayanov, and I'm this team's
coach (and also all other teams from my university). In reality I'm
the director of Programming Competitions ...
Meanwhile the season 2009-2010 was coming, the last in the team's history.
The contest has
121.
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...
), but at least this one has a picture! By this time anyone with a history of
participation in my
Tutorial of April Fools Day Contest 2016
122.
TCR trick: Line hashes Hey guys. I wanted to share a neat trick regarding the Team Contest Reference (TCR) that we're allowed to bring to ICPC contests, for example. I got the idea after spending many minutes debugging a Convex Hull implementation I wrote directly from my TCR in the middle of a regional contest. I knew the implementation in the TCR was correct, but I had probably made a typo somewhere in the code when I was inputting it, but it was impossible to find.
The idea is to store hashes of the code in the TCR. For example, for each code snippet in the TCR we could store its MD5 sum. Then after typing up some snippet from the TCR, we can check that the MD5 sum of the file matches the MD5 sum in the TCR. This is however not very beneficial, since we can only check whether or not our code is identical. We don't get any information about where the error was made.
Another idea is to store the MD5 sum of each line of each code snippet in the TCR. This can take up much space, but the first couple of ...
). With this in the command history and using the 'gv' shortcut to reselect
previous selection, it
123.
Have you already seen the history of ratings on clist? Such graphs can be seen [here](https://clist.by/coder/aropan/):
But of course it is better to look right [here](https://clist.by/coder/tourist/).
##### Can I have the same ones??
Sure. [Sign up](https://clist.by/login/), [add your accounts](https://clist.by/settings/accounts/) and [enjoy](https://clist.by/coder/).
**UPD**
There is also a rating distribution for different resources, [for example](https://clist.by/resource/codeforces.com/):
But its relevance may diverge due to inactive participants.
Have you already seen the history of ratings on clist?, :  is a country with very rich history. Through the ages it participated in Greco-Persian wars, accepted Islam, was under Shah rule and now known as Islamic Republic of Iran since revolution in 1979.
Tehran, capital of Iran, is modern city, but with a lot of historic places throughout the city, like palaces of last Iranian Shahs, which is now [museum complex](http://en.wikipedia.org/wiki/Niavaran_Palace_Complex) or [Grand Bazaar](http://en.wikipedia.org/wiki/Grand_Bazaar,_Tehran), both of which contestants visited 2 years ago.
As for food, get ready for some tasteful...
://en.wikipedia.org/wiki/Iran) is a country with very rich history. Through the
ages it participated in, [Iran](http://en.wikipedia.org/wiki/Iran) is a country with very rich history.
Through the ages it
125.
Memories: ACM-ICPC World Finals 2009 <p>
<img src="http://lh6.ggpht.com/_mSdPzSw5zAo/S2KKSsTdWyI/AAAAAAAADGE/vpMUDSuenS0/IMG_0494.JPG" style="float: left;margin: 1.0em;"> The World Finals of the 33rd
International Collegiate Programming Contest for was held in the
capital of Sweden, Stockholm. The contest was held in Europe for
the third time: in 1999 it was held in Eindhoven (the
Netherlands), in 2004 - in Prague (the Czech Republic). It was the
first time the key role in the competition had been played by the
University: it was held in the library of the Royal Technological
University. One hundred best teams of the world took part in the
final, while the preliminary rounds saw 7109 teams from 1838
Universities and 88 countries competing. It was the sixth time the
Saratov State University had took part in ACM-ICPC World Finals. </p>
<p> The participants were placed in two hotels in the historic centre of
Stockholm, Gamla Stan district. Our team was placed in the Gran...
teams' trainers and instructors, and on the local TV. During the broadcast the
history of ACM
126.
My Course "Advanced Algorithms and Data Structures" at Harbour.Space University <img src="/predownloaded/c0/52/c052c92fc998292e9705f9924413b581d13515ba.jpg" style="float:right; margin: 0 1em;"/>
Hi, Codeforces!
This is not an ordinary post from me. This is not an announcement of new features or a championship, but I'm no less enthusiastic.
I am glad to inform you that from January 29 to February 16, 2018 I will be giving the course <a href="https://goo.gl/u5nTmk">"Advanced Algorithms and Data Structures"</a> in <a href="https://goo.gl/zDSsaQ">Harbour.Space University (Barcelona, Spain)</a>. The course will be in English. The students of this course will not only be students of Harbour.Space, but is open to all! Who wants to join?
This course isn't just for Harbour.Space students, it is also open to Codeforces participants, who will be offered a special price, 1000 EUR. The cost does not include travel or accommodation.
<center style="margin:20px;">
<a style="font-size: 24px; padding: 8px 14px; background-color: #673AB7; color: white;" href="https:/...
opportunity to meet and talk. I'm happy to share stories about the history of
Codeforces and development
127.
Latest chat-GPT only have a codeforces rating of 392 Now the newest GPT have published its academic performance. Here is the picture.
We can see from this picture that latest Chat-GPT have very outstanding performance at all kinds of exams GRE (beat me hard in GRE verbal), SAT, LSAT....
But for codeforces, original GPT only have a rating of 260, the GPT-4 is slightly better, with a rating of 392. Even a newbie can beat chatGPT-4 now (2023-03-14). Codeforces is the only one that GPT behave below 5%. Therefore, I am proud to say, competitive programming, like us codeforces, is one of the hardest obstacles chat-GPT will overcome.
The reason why I post this, is that many people, including me, worries that chat-GPT will destroy the competitive programming, like alphago destroy the go.
I am not saying it will not. However, think about it, why alphago vs Sedol lee or Jie Ke is most famous and shock the whole world?...
era, and we contestants will all witness the history., witness the history.
128.
(Plenty of) useful blogs in CodeForces Here are some useful blogs I found in CodeForces.
Note that:
- This list can be treated as an extension of [catalog](https://codeforces.com/catalog), since much of these tutorials are included in catalog but the others are collected by myself.
- The same blog may be included in this post twice or more.
- Blogs to ask questions are **NOT** included in this blog, since they seemed not quite useful to CP.
- If there are any blogs that I have missed, please tell me in the comment section. Thank you very much.
Hint: you can use Ctrl+F to search for information here.
# General Advices
## Micellaneous
- [How to use Codeforces [GUIDE]](https://codeforces.com/blog/entry/99660)
- [[Tutorial] The command line: how to read input from file without #ifdef and much more](https://codeforces.com/blog/entry/102287)
- [After a Round FAQ](https://codeforces.com/blog/entry/103654)
- [[Tutorial] How to read editorials](https://codeforces.com/blog/entry/123882)
- [Pro Tips — get them whi...
the history of ratings on clist?](https://codeforces.com/blog/entry/77516) -
[Codeforces Problem, history of some recurring problem](https://codeforces.com/blog/entry/62331) -
[[Tutorial] Expected
129.
Topcoder SRM 500 Please note due to Daylight Savings, TopCoder time has changed to Eastern Daylight Time or UTC -4.<br>
<br>
TopCoder(R) Single Round Match <span class="il">500</span> is scheduled
for Saturday, March 19, 2011 at 12:00 UTC -4 hours. In recognition of
this milestone, TopCoder will be awarding 5,000 in cash prizes plus
more! So get ready for the most prestigious TopCoder <span class="il">SRM</span> in years and give yourself a chance at becoming part of history!<br>
<br>
<span class="il">SRM</span> <span class="il">500</span> will begin at
12:00 UTC-4 with registration opening 3 hours prior to match time.
Registration will be limited to 2,100 slots on a first come first serve
basis so be sure to register early!<br>
<br>
Please be sure to check here for the start time in your time zone:<br>
<a href="http://www.timeanddate.com/worldclock/fixedtime.html?&day=19&month=03&year=2011&hour=12&min=00&sec=0&p1=179" target="_blank">http://www.time...
in years and give yourself a chance at becoming part of history!
130.
Cormen Medal 2011 <h4> On January, 27 we summed up the results and rewarded the laureates. They are: </h4>
<center>
<table>
<tr>
<td>
<img src="http://assets.codeforces.com/images/cormen-2011/tourist.png" style="height:200px;"/>
<br>
<small>[[user:tourist]] <br/> The Best Codeforces Participant 2011</small>
</td>
<td>
<img src="http://assets.codeforces.com/images/cormen-2011/Ripatti.png" style="height:200px;"/>
<br>
<small>[[user:Ripatti]] <br/> The Best Codeforces Problemsetter 2011</small>
</td>
<td>
<img src="http://assets.codeforces.com/images/cormen-2011/Alex_KPR.png" style="height:200px;"/>
<br>
<small>[[user:Alex_KPR]] <br/> The Best Codeforces Blogger 2011</small>
</td>
</tr>
</table>
</center>
<ul> <li> The Best Codeforces Participant 2011: Gennady [[user:tourist,2012-01-27]] Korotkyevich. We've recounted the rating taking only the 2011 rounds into consideration. Gennady topped the table well ahead of everybody else! You can follow <a href="http://codeforces.com/contes...
[cut]
Here is our announcement of the 2011 medals. For history, so to put it
131.
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: *...
before simulating your entire contest history (It should be fine ;)).
132.
A New Bayesian Contest Rating System (Elo-MMR) **UPDATE: the [new rating system paper](https://arxiv.org/abs/2101.00400) will appear in the Web Conference 2021!**
Last year, I [published ratings](https://codeforces.com/blog/entry/68288) using a contest rating system that I had developed at the end of 2015. Back then, I promised to eventually write in detail about the system's inner workings.
Over the past week, I've cleaned up and optimized the code: it now takes 24 minutes to process the entire history of Codeforces on my small laptop!!!
More importantly, I cleaned up the paper. Please ignore the last sections for now, as they're incomplete, but the main sections that explain how the rating system was derived are now ready! I claim my Elo-MMR is a more principled extension of Elo/Glicko to the programming contest setting, with nicer properties than the systems that contest sites currently use.
The main work that remains to be done are quantitative empirical studies comparing the properties of the different ratings syst...
entire history of Codeforces on my small laptop!!!
133.
Challenge for Div2 Students <table>
<div style="font-size: 16px;">
Hi all and <span style="color:red;">happy New Year!</span> <br>
<p>I am [user:chessmaster,2017-02-03], and ordinary student from Uzbekistan, who has been participating <span style="color:blue;">ACM ICPC</span> semifinals of <span style="color:blue;">NEERC</span> region. During the first attempt, my team managed to solve two problems and was a bit higher than bottom in the scoreboard. However, this year we couldn’t solve anything (let’s not talk about places). At that moment, I realized that NEERC is a hard nut to crack. Being blue (not to mention green and cyan), it is way too early to dream about first-degree certificates or proceeding to Finals. So I said to myself: “Either you raise your rating to 2000 or you skip <span style="color:blue;">ACM ICPC 2017</span>. You won’t even register your team!”. Then I told my friends about this and four of them joined me. Now I want to offer this challenge to all div2 students, who want not only participa...
history
134.
Let's face it, Polygon is horrible 
Polygon is not world's greatest evil. Polygon doesn't even have a particular defect that makes it horrible. You can't say what's exactly wrong with Polygon. Polygon seems to work, it seems like every feature is supported, but if you touch it here it will fall apart, and if you touch it there a problem (pun not intended) will appear. Or not, depending on your luck. Polygon is like PHP. For those who haven't read the famous rant, I'll cite it for you:
> I can't even say what's wrong with PHP, because-- okay. Imagine you have uh, a toolbox. A set of tools. Looks okay, standard stuff in there.
>
> You pull out a screwdriver, and you see it's one of those weird tri-headed things. Okay, well, that's not very useful to you, but you guess it comes in handy sometimes.
>
> You pull out the hammer, but to your dismay, it has the claw part on both sides. Still serviceable though, I mean, you can hit nails with the middle of the head holding it...
cvs or from git, I don't know. It has linear history. There are revisions. A
list of changes in each
135.
Elimination Round Editorial — Bayan programming Contest 2014-2015 ### A. New Rock Paper Scissors
The $O(n^2)$ solution is straight forward, although it can be solved in $O(n)$ but it was not required. Even the $O(n)$ seems easier to implement, but some cases might be missed. That's why the easiest problem of the contest turned out to be a little tricky. You see both kind of solutions in the scoreboard.
### B. Bayan Health Bracelet
In this problems you had to find the first condition that is met. If carefully implemented one can get accepted with no hassle.
### C. Grid History
The following two statements should hold for a valid grid:
+ If the board is checkered, two cells have the same parity, if and only if they are colored the same.
+ Let $x$ be the value of a cell, and $y$ be the value of the first cell with greater value than $x$. The length of the shortest path from $x$ to $y$ among the cells with value greater than or equal to $x$, is not greater than $y - x$.
+ two greatest values of the board must differ by one.
Checkin...
### C. Grid History
136.
Active/Inactive status for CF users If you do not participate in rated rounds for 6 months you get status “Inactive”. Does it mean you are really inactive compared to others? What is a typical interval for users between their contests?
I ran [my script ](https://github.com/NataIss/codeforces) on Oct 31 2021. It collected information about intervals between rounds for all users who have at least one interval, that means who has taken part in at least two rounds. It discovered 283412 appropriated users and counted 4552393 intervals.
95% of intervals are shorter than 113 days.
Percentage of intervals shorter than 183 days is 97,09%.
Mean value is 27,5 days, mediane is 7 days.
Let’s look at the distribution of duration for intervals less or equal to 183.
So it is totally ok to mark users as inactive after a six-month absence. But I was just curious to find out somebody who came back after being inactive for a long time. What ...
It’s a pity that their history remains hidden, why they left, why they decided
to return, I do not
137.
ICPC Alumni meeting on July 6 in Saint-Petersburg <img src="/predownloaded/90/d5/90d595b664570b1e4fb71c089e69bcb6fc491fce.png" align="right" style="height: 220px; margin: 10px 35px 20px;" alt="text"/>
We glad to announce the first ICPC Alumni event happening in Russia!
ICPC Foundation is currently working on building the ICPC Alumni association across the globe and we're happy to announce our big reunion event to be held at a very special location — ITMO University, St.Petersburg, Russia.
We will be extremely honored to welcome you and your colleagues/classmates on this special day. In addition to this being a fun reunion for local ICPC participants, we will be recognizing the accomplishments of various ICPC volunteers who make the show happen each year!
ICPC Alumni Reunion Dinner will be held on Saturday, [July 6th, 2019](https://www.timeanddate.com/worldclock/fixedtime.html?msg=ICPC+Alumni+meeting&iso=20190706T17&p1=352) at ITMO University (St.Petersburg, Russia) on [Birzhevaya line 14-16](http://www.ifmo.r...
to be shown at the event added to the ICPC History Archives and/or shared over
ICPCNews, please share
138.
Discussion on a bug of mojibake(especially regarding Chinese) in the Ghosts uploading in gym Discussion on a bug of mojibake(especially regarding Chinese) in the Ghosts uploading in gym
==================
Hello guys, I am the contest uploader of [contest:103366] and by the time I uploaded it, I encountered a serious bug of mojibake when uploading Ghosts containing Chinese characters. As it is at the middle of Chinese algorithm contests season, I find it necessary to discuss this bug in public as well as to provide a temporary solution to this bug for Chinese uploader or anyone who suffering from this bug.
Discovery of the bug
------------------
In October $25^{th}$, after I upload the Ghosts for the [contest:103366] through FTP servers, all the Chinese characters in the team name became mojibake as the screenshot below.
As I was convinced that gym supports the unicode display of team name in Ghosts, I consulted another uploader who have successfully uploaded team name with Chinese characters onl...
bottom of contestant list with their name in Russian. As they have no
submissionhistory, they will
139.
codeforces Codeforces
| In English По-русски
pathetique | Logout
HOMETOPCATALOGCONTESTSGYMPROBLEMSETGROUPSRATINGEDUAPICALENDARHELP
→ Pay attention
Before contest
Educational Codeforces Round 162 (Rated for Div. 2)
2 days
Register now »
→ pathetique
pathetique
User''s contest rating in Codeforces communityRating: 1448
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Settings
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# User Rating
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# User Contrib.
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# Name
1 X-Camp 402H 2022 Fall
View all →
...
By Artyom123, history, 12 days ago, In English Hello, Codeforces! We're glad to
invite you to take, By Vladosiya, history, 9 days ago, translation, In English Hello! Codeforces
Round 925 (Div. 3, By george_stelian, history, 7 days ago, In English Dear Codeforces,, By pashka, history, 3 days ago, In English Hello! On Sunday, February 18, 2024
at 04:05UTC-8 will
140.
Bubble Cup Conference Hello, Codeforces!
As you know from this [post](http://codeforces.com/blog/entry/20072) and this [post](http://codeforces.com/blog/entry/19957), [Bubble Cup](http://www.bubblecup.org/) is a programming competition organized by [Microsoft Development Center Serbia](http://www.microsoft.com/serbia/mdcs/). This year was held the first BubbleCup Conference where competitions gurus talked about competitive programming and more!
And I wanted to share with you some great and useful talks. I sorted them in order of when they were presented, because some part of one lecturer is in the video of the other lecturer. I would suggest you to start from begging. Enjoy :)
Michal Forisek ([user:misof,2015-10-21]) — talked about how it's easy to get discouraged in competitive programming; how to practise, **do what gives you the largest benefits**; about new point of view through, at first glance, easy graph problem.
- [BBC8 Lecture — Michal (part 1)](https://www.youtube.com/watch...
Marko Panic, Andreja Ilic, Zeljko Nikolicic (MDCS crew) — talked about history
of Bubble Cup, Mike Mirzayanov ([user:MikeMirzayanov,2015-10-21]) — talked about his history
of competitive
141.
Звезда спортивного программирования Marek Cygan получил престижный грант Европейского исследовательского совета Marek [user:marek.cygan,2016-11-05] Cygan из Университета Варшавы [получил престижный грант](http://en.uw.edu.pl/young-scientist-and-algorithms/) ERC (Европейского исследовательского совета) — 1,4 млн евро для работы над алгоритмами, которая будет проводиться в Варшавском университете и называется “Technology transfer between modern algorithmic paradigms”.
Marek — звезда олимпиадного программирования. В 2005 году он выиграл [Google Code Jam](https://community.topcoder.com/pl/?module=Static&d1=google05&d2=overview), в 2007 вместе с Marcin Pilipczuk и Filip Wolski [выиграл ACM-ICPC в Токио](https://icpc.baylor.edu/community/history-icpc-2007), в 2009 занял 3-е место в [TopCoder Open в Лас-Вегасе](http://www.topcoder.com/tc?module=Static&d1=tournaments&d2=tco09&d3=overview&d4=overview).
Он получил много стипендий от государственных учреждений, в том числе от Министерства науки и высшего образования, Фонда польской науки и Национального научного центра. Молодой ученый п...
Pilipczuk и Filip Wolski [выиграл ACM-ICPC в
Токио](https://icpc.baylor.edu/community/history-icpc-2007), в, Wolski won the [ACM-ICPC in Tokio.](https://icpc.baylor.edu/community/history
-icpc-2007). As a Phd, -ICPC в Токио](https://icpc.baylor.edu/community/history-icpc-2007), в 2009
занял 3-е место в, ://icpc.baylor.edu/community/history-icpc-2007). As a Phd student of Institute
of Informatics of the
142.
My Course at Harbour.Space University: Advanced Algorithms and Data Structures (January, 2019) <img src="/predownloaded/c0/52/c052c92fc998292e9705f9924413b581d13515ba.jpg" style="float:right; margin: 0 1em;"/>
Hi, Codeforces!
I am glad to announce and invite you to the second launch of my course on algorithms and data structures.
On 7-25 of January, 2019, I will be giving the course <a href="https://goo.gl/u5nTmk">"Advanced Algorithms and Data Structures"</a> at <a href="https://goo.gl/zDSsaQ">Harbour.Space University (Barcelona, Spain)</a>. It will be in English, and is not limited to Harbour.Space students — anyone is welcome! Who wants to join?
This course isn't just for Harbour.Space students, it is also open to Codeforces participants, who will be offered a special price, 1000 EUR. The cost does not include travel or accommodation.
<br/>
<center style="margin:20px;">
<a style="font-size: 24px; padding: 8px 14px; background-color: #673AB7; color: white;" href="https://goo.gl/u5nTmk">Register for the Course →</a>
</center>
The curriculum will i...
opportunity to meet and talk. I look forward to share stories about the history
of Codeforces and
143.
Wow! You received a rating of -501 in the CodeTON round. Share it! Is this the highest rating drop in the history?
Is this the highest rating drop in the history?
144.
Editorial for A2SV G123 After Study Contest 3 Special thanks to [user:feysel_mubarek,2022-06-03] for preparing the contest.
Contest Link: https://codeforces.com/contests/385438
### [A. Helpful Maths](https://codeforces.com/gym/385438/problem/A)
By: [user:Abel-Mek,2022-06-17]
<spoiler summary="Tutorial">
Xenia wants to compute the total of integer summands, but she can only do it if the summands are sorted in a non-decreasing manner, therefore we may assist her as follows:
- step 1: remove the “+” character from the given string.
- Step 2: sort the summands in an increasing order.
- Step 3: replace the “+” character between the summands.
</spoiler>
<spoiler summary="Solution">
~~~~~
input = input().split("+")
input.sort()
li = []
for i in range(len(input)):
li.append(input[i])
if i < len(input) - 1:
li.append("+")
string = "".join(li)
print(string)
~~~~~
Time complexity: $O(nlogn)$ Space complexity: $O(n)$
</spoiler>
### [B. Sereja and Dima](https://codeforces.com/gym/385438/probl...
complexity: $O(n)$, $n$ is number of rounds Space Complexity: $O(n)$, the
history array is a size, through the history array to find the first person to score at least m points
first. 5. Check if, ~~~~~ score = {} history = [] winners = set(), A list called history to store the inputs we are given in each round. This
comes in handy when we, roundScore = {} for i in range(len(history)): name,score = history[i].split()
score
145.
Why rating losses don't matter much (alternate timelines part II) Some time ago I posted [this blog](https://codeforces.com/blog/entry/79415), which showed the diminishing effect of a huge rating loss over a period of many contests. Recently, I decided to try to show this effect a bit more broadly. So I extended it to be a bit more extreme and simulated my entire contest history while **ignoring all rating losses**. That is, I ran through every contest I was ever rated for and calculated the expected rating change with [cfviz](https://cfviz.netlify.app/virtual-rating-change.html), but maxed out every rating change with $0$.
Now, the question is, how much of an effect did ignoring rating losses have? I give more details in **[this video](https://www.youtube.com/watch?v=E-aylp6MZnM)**, at the **[6:56](https://youtu.be/E-aylp6MZnM?t=416)** mark **(said video also has many more tips, generally being about how you can learn more from the contests you do, which is not-so-subtly the whole point of this blog)**. But, essentially...
the "optimistic" rat...
contest history while **ignoring all rating losses**. That is, I ran through
every contest I was
146.
Two New Features at the Competitive Programming Hall of Fame Hi Codeforces!
I'm happy to show you two new features, that I've added to the Competitive Programming Hall of Fame website recently. You can find both of them at the [main page](https://cphof.org):
The "Top-100" page allows to see the top performers in major competitions, and the top prize winners.
<spoiler summary="How the Top-100 page looks like">
</spoiler>
The "Advanced" pages contain the lists of participants who advanced to the finals of the upcoming contests. For each of the finalists, there is a bunch of interesting information like ratings and performance history. Most of the columns of the table are sortable. Now there are two advancers lists available: [Finalists of Topcoder Open 2022 Marathon](https://cphof.org/advanced/tco_mar/2022) and [Finalists of Topcoder Open 2022 Algorithm](https://cph...
of interesting information like ratings and performance history. Most of the
columns of the table, performance history. Most of the columns of the table are sortable. Now there
are two advancers lists
147.
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...
since 2001. Rich in history, It's considered to be one of the most prestigious
organizations when
148.
What happened to Topcoder? Hello friends!
I hope a few of you might still remember me. This old dinosaur participated in very early rounds of Codeforces, and before that did Topcoder for a number of years. I've been away from competitive programming for several years now, but the recently started [Advent of Code](https://adventofcode.com/) rekindled the spark, and I proceeded to open Topcoder arena and participate in the recent SRM.
To my utter befuddlement, there were less than 100 participants in Div 1 in this SRM — and looking through recent [match history](https://www.topcoder.com/tc?module=MatchList), it seems to be a fairly standard participation rate for a while now. For comparison, back in the good days Topcoder Div 1 routinely had several hundreds of coders.
I've got to admit that seeing this saddened me considerably — I have a ton of fond memories of competing at Topcoder, like rushing those 250-pointers, taking perpetually unsuccessful stabs at 1000-pointers, the violent heartbeat...
looking through recent [match history
](https://www.topcoder.com/tc?module=MatchList), it seems to be a
149.
Codeforces Stats Android Application The first Codeforces Android Application is now available on the Google Play Store.
You can download it here-
https://play.google.com/store/apps/details?id=com.innsolutions.codeforcesstats
This application makes extensive use of the Codeforces API which allows you to do the following things-
I. Powerful Problem Filter
Search through thousands of Codeforces Problems in the blink of an eye.
1. Problems Search By Tags
Did you study trees yesterday & feel like solving some questions on trees? Well, look no further. This app lets you filter the Codeforces Problems by tags.
Want to practice questions which involve the concepts of both dynamic programming as well as probability? Just type those tags & only those problems would be shown which involve the knowledge of ALL the tags given.
2. Custom Problem Search
a. Find all the problems of a particular contest.
b. Find all the problems of a particular index(A,B,C,D,E,F).
c. Find problems which contain the word(string) gi...
2. User Rating Change History The Rating Change History which includes the
details of all the
150.
Codeforces: Copying of Contests and Gyms Hello!
In this post I will talk about recent innovation in Codeforces.
It is noticed that many coaches used the opportunity to change the start of the training/rename it for personal purposes (to host group trainings). This leads to confusion and inconvenience for other members of the community.
<img src="/predownloaded/03/bf/03bfe17abe456afe14ac93cd643586fd35301a51.png" style="float:right;margin:0 1em 1em 1em;width:190px;"/>
To keep everything in order, we changed the rules for editing gym contests. Now a coach can change the name/start time/description of a gym if it is not public or the last update was made not later than a week ago. A week after editing a gym, it becomes the history of Codeforces and coaches lose an opportunity to make edits in it.
You cat ask "how do you give a training in a group, specifying the start time?" Now there is such a way!
To allow more convenient re-use of past trainings, as well as regular contests, it was possible to copy past train...
than a week ago. A week after editing a gym, it becomes the history of
Codeforces and coaches lose an
151.
To all ICPC participants and coaches about ICPC Yinchuan Site _If you don't know what happened, you can see this blog: [Corruption, Cheating at ICPC Yinchuan](https://codeforces.com/blog/entry/90897)_
Just about one week ago, we endured an earthquake on CN-ICPC.
Cheating, Corruption, Chaos, that is what NXIST brought to us. And yesterday, this petty clown posted a ridiculous blog, brag their "Gold Medal Team" to all of us. Many honest participants devote years of time to training and then win a hard-won gold medal. But now, a cheater, tells us how their "hardworking“ lead them to the gold medal?? **THIS IS AN UNFORGIVABLE INSULT TO ALL PARTICIPANTS AND COACHES.**
Thought Wu Yonghui said C. J. Hwang will proceeding the investigation and given a result on June 7, but we all know what will happen just like the 2019 Yinchuan Site. So now, please join this boycott of NXIST's cheating and corruption, send this joint letter to ICPC Contest Manager — [email protected], and ask them for the response.
**"NXIST holding the regional con...
competition. Now we are enduring the darkest day in ICPC's history. We won't
let it become something filled
152.
The history of the competitive programming The History of Competitive Programming: A Look Back
Competitive programming has come a long way since its early days. In this blog post, we'll take a look back at the history of competitive programming, from its origins to its current state.
The Origins of Competitive Programming
The first recorded instance of a competitive programming contest took place in 1974, when the Association for Computing Machinery (ACM) organized a programming competition for college students. The competition was called the International Collegiate Programming Contest (ICPC) and it was held annually. The ICPC was limited to colleges and universities in North America, but it quickly gained popularity and expanded to include institutions from other countries.
The Early Years of Competitive Programming
In the early years, competitive programming was limited to a single location, with participants working on computers provided by the organizers. The competition format was simple: participants were ...
The history of the competitive programming, look back at the history of competitive programming, from its origins to its
current state., I hope this brief overview of the history of competitive programming was
informative and, The History of Competitive Programming: A Look Back
153.
Helping Contestants Help Us All or Competition Pitfalls During my competition history I've collected a vast amount of different fail stories. And those usually come in two flavours. You either get an aftertaste of a personal failure or you get a feeling that you were helped by organisers in your adventure. And it's always helpful to try and learn something from these failures. The first ones are kind of personal, and only affect you or your team, so they are not that interesting to talk about. The second ones however are more important. First of all, this is a direct feedback to the organisers, in hopes that it might make future contest better. And then you usually try to use that feedback yourself when you move on the organisers side in an attempt to make sure that you avoid setting all those pitfalls that you were annoyed about when competing. So here I'm going to try and describe two types of pitfalls that in my opinion the organisers can deliberately or accidentally set that helps teams to embark on a wonderful journey to fail-land a lo...
During my competition history I've collected a vast amount of different fail
stories. And those
154.
[Unrelated] Brief Summary of “On the Six Fallen States” **Disclaimer: This is completely unrelated to competitive programming.** <br><br>
In the light of the recent blog posted (and deleted) by sparky_master_wch1226 and qwaszx_ak_ioi, coincidently, the same classic Chinese article, “On the Six Fallen States” (六國論, 六国论) is mentioned. This article was written by Su Xan (蘇洵, 苏洵) during the Northern Song Dynasty (北宋), and it is now shared by users living in Botswana (probably not) and Japan on a competitive programming platform after almost a millennium. Undoubtedly, this is one of the best articles in the history of China. Indeed, in most Chinese-speaking places, this article is introduced to students. Not only does this article demonstrate high-level argumentation skills, but at the same time reflects the history of the warring states period (戰國時代, 战国时期) to the situation at that time and allows readers to learn from the past.<br><br>
Starting with the first paragraph, <br><br>
六國破滅，非兵不利，戰不善，弊在賂秦。賂秦而力虧，破滅之道也。 或曰：「六國互喪，率賂秦耶？」曰：「不賂者以賂者喪。」蓋失強援...
almost a millennium. Undoubtedly, this is one of the best articles in the
history of China. Indeed, to admonish the monarch of Northern Song and asked him to learn from history.
(借古諷今)
155.
Codeforces: two months after the 5th anniversary (Feb.-Mar., 2015) Hi!
**It is only a day before the end of [the fundraising campaign dedicated to the 5th anniversary of Codeforces](/5years).
We are glad and grateful for your help and support. We are working hard to justify your and our own expectations.**
For those who are not accustomed to rush, remember that you still have a little time to join [the remarkable list of our friends](/5years/supporters) — help
us and get a gift from the Codeforces team!
When summing up, of course, we mostly want not to count money, but to assess progress and the work done. I looked at all of our commits to Codeforces and Polygon, and made a digest of changes.
I did not include to the digest improvements in the depths of system's backend (although stability progress should be visible), infrastructure jobs, org. work around the championships — but, believe me, there were many items too.
And here is the list of our achievements for about two months after anniversary.
[cut]
##...
problem locks in history of participation (by double click in standings
table). ### Polygon, history of participation (by double click in standings table).
156.
About my teammate Have you read my first post? If no, please read it before this.
My, teammate, [user:Marzipan,2023-12-31]
Has had a registration on codeforces for over 4 years and he decided to publish a post on his blog for the first time.
And this post immediately became the top -2 in number of votes on Codeforces!
And my teammate himself is top -1 in contribution and in total contribution of all posts.
Codeforces has been waiting for my teammate's word for 14 years! And now, after so many years of waiting, we have heard it and Codeforces is covered in house.
Hooray, long live [user:Marzipan,2023-12-31]!
In all seriousness, it's pretty sad. Arseniy ([user:Marzipan,2023-12-31]) prepared really cool problems, he tried to make the best samples, he added all the little testcases to the samples that broke the testers' decisions.
The round was prepared by guys from Lyceum 31, including [user:Marzipan,2023-12-31], and their tasks are really great.
I think that because of task H (and even...
But please put dislikes on his post))))) let him go down in history as a top -1
post with his first
157.
Source Code Viewing <div><div>Hello to everyone.</div><div><br></div><div>The latest news - now you are able to see the source code of the solution. During the contest you can view your own solutions only, but when the contest is finished you can view the solutions of any other participant. The table with the solutions is available via the problemset page, the solutions there are sorted by the program length. Pay attention, please, that you are free to change the sorting criteria using the option at the bottom of the table. </div><div>There is another principle that gives you the chance to view the source codes of solved (during the contest or practice) solutions only. Personally, I regard the principle "everyone sees everything" as more suitable for our regular contests. Am I right?</div><div><br></div><div>When you run a contest within your private community, you'll be able to set up your own principle for viewing solutions (or to switch off this function at all). But this functionality is un...
Ctrl+click) to view the submissions history.
158.
On the question of diversity on Codeforces #### Rating
Codeforces has ranks "candidate master", "master", "grandmaster", "international grandmaster" and "legendary grandmaster". I propose renaming these titles for the following reasons:
1. They are insultive to differently-abled people who can't reach high results and thus can't "master" competitive programming.
2. "master" sounds like a reference to master/slave terminology, it needlessly references awful history. I believe it's inappropriate for such a great platform as Codeforces.
I think the following titles should be used instead:
1. "candidate master" -> "candidate professional"
2. "master" -> "professional"
3. "grandmaster" -> "genius"
4. "international grandmaster" -> "international genius"
5. "legendary grandmaster" -> "legendary genius"
Additionally, I believe "genius" is more descriptive than "master" or "grandmaster".
I want to note that a similar change was adopted by many projects:
1. [Python](https://bugs.python.org/issue34605) — Avoid m...
needlessly references awful history. I believe it's inappropriate for such a
great platform as
159.
Baltic Olympiad in Informatics 2023 It seems that Codeforces is flooded with spam bots now. Unrated spam bots have a long history on this site. The only difference is that now they work in an automated matter, instead of people who think like bots. [So why are they able to write posts in the first place?](https://codeforces.com/blog/entry/115073)
Enough rant, Baltic Olympiad in Informatics 2023 is held in Lyngby, Denmark. Good luck to all participants!
Day 1 mirror starts in an hour. Let's discuss the problems after the contest.
* [Official website](https://boi2023.org/)
* [Day 1 mirror](https://boi23.kattis.com/contests/boi23day1open)
* [Day 2 mirror](https://boi23.kattis.com/contests/boi23day2open)
It seems that Codeforces is flooded with spam bots now. Unrated spam bots have
a longhistory on
160.
Historic moment Hello, today in CodeTON round #3, one of the most epic moments in cf history has happened. It's about [user:tourist,2022-11-06].
Did he finally cross 4000 rating? No.
Today, he got owned by his archenemy, python gigachad [user:conqueror_of_tourist,2022-11-06].
Congratulations to [user:conqueror_of_tourist,2022-11-06]. Good job, king!
Hello, today in CodeTON round #3, one of the most epic moments in cf history
has happened. It's
161.
Codeforces improvements suggestions ### Hacking improvements:
- Being able to see the defender's submission from the open hacking page. It is kind of annoying that you have to open the person's profile and then go to his submissions just to see his/her submission.(ADDED thanks to Mike!)
- Fixing **illegal contest ID** bug when trying to hack a person through **submission window** in open hacking.
- Splitting the hacking log(open hacking) into pages. The log sometimes can be huge which would make loading the page slower on low-end devices(like mobiles).(ADDED thanks to Mike!)
### Searching improvements:
- **Standings search** only searches through the current page which is not a public search. Making it a public search would be a lot better!
- Improvement for codeforces search. Instead of searching for the **exact word/username**, it would search for the **nearest** result. Searching users' handles like this would be a lot easier.
### Mobile improvements:
- Improvement to submission window on mobil...
. Instead, It should open the **submission history window**.(suggested by
[user:nutzboi,2020-03-13])
162.
A Journey Through Time: The History of the International Collegiate Programming Contest (ICPC) **Introduction**
The International Collegiate Programming Contest, known worldwide as ICPC, is a prestigious and highly competitive programming competition that has a rich history dating back to the 1970s. This article delves into the origins and evolution of ICPC, highlighting the pivotal moments, growth, and impact this competition has had on the world of computer science and programming.
**The Inception**
The ICPC had its humble beginnings in 1970 when a group of students and faculty from Michigan State University organized the first-ever programming competition. At that time, the contest was confined to a local level, and it aimed to foster problem-solving and teamwork skills among computer science students. It was an invigorating way to encourage students to explore their problem-solving abilities and delve into the world of algorithms and data structures.
**The Transition to International**
The ICPC's status as an international event began to take shape in the late...
A Journey Through Time: The History of the International Collegiate Programming
Contest (ICPC), highly competitive programming competition that has a rich history dating back
to the 1970s. This, prestigious and highly competitive programming competition that has a rich
history dating back to, The history of ICPC is a testament to the power of academic competitions in
shaping the future of
163.
Submissions skipped in GR23 Hi [user:MikeMirzayanov,2022-10-15],
My submissions were skipped from today's contest due to plagiarism checker for problem E2. As stated by others, problem E2 had a very similar idea to BOI 2022 communication, and the main logic of the code from my solution was copied from a previous submission for that problem (https://oj.uz/submission/592003, you can see that this code was submitted months before this contest).
I'm not sure whether this problem was intentionally copied or not — but I don't believe that I broke any Codeforces rules with this submission, since the source code was published before the contest started. Please review my case, thanks!
EDIT: My submission https://codeforces.com/contest/1746/submission/176378653
EDIT 2: In case evidence of search history cache is needed (my time zone is GMT-7, so 8:47 AM on October 15th is during the contest for me):
EDIT 2: In case evidence of search history cache is needed (my time zone is
GMT-7, so 8:47 AM on
164.
Invitation to Alkhwarizm — 2018 
Hello, Codeforces!
I would like to invite you all to [Alkhwarizm 2018](https://www.codechef.com/ALKH2018), the flagship coding event of [Aparoksha](https://aparoksha.org/) — The Annual tech fest of IIIT-Allahabad.
It will contain 10 tasks of varying difficulty and you will get 5 hours of time to fight this fierce battle of _Codditch_(another version of [Quidditch](http://harrypotter.wikia.com/wiki/Quidditch)).
The contest will be an [External rated contest](https://blog.codechef.com/2017/03/09/a-star-studded-rating-system/). We are happy to announce that [Alkhwarizm 2017](https://www.codechef.com/ALKH2017) was the first External rated contest in the history of Codechef and this year [Alkhwarizm 2018](https://www.codechef.com/ALKH2018) is the first External rated contest for both Divisions after the [New Rating Division](https://www.codechef.com/ratings/divisions) system on Codechef.
The problem...
) was the first External rated contest in the history of Codechef and this year
[Alkhwarizm 2018
165.
Codeforces Helper new features: Compete and History Hi,
I have added compete and history to [Codeforces helper](http://codeforceshelper.herokuapp.com).
**Compete**
Find how many rounds you have won against your rival. Mine is [user:hell_hacker,2020-08-26].
**History**
Find how you have performed in various type of contests Div. 2, Div. 3, Educational, Div. 1 + 2 etc.
TODO features:
- Track solved problems of each contest
If you have any feature please suggest down in comments. Thanks.
Codeforces Helper new features: Compete and History, **History**, Hi, I have added compete and history to [Codeforces helper](http, I have added compete and history to [Codeforces
helper](http://codeforceshelper.herokuapp.com).
166.
Testlib 0.9.4 Это уже стало доброй традицией, что когда я еду в поезде или нахожусь в командировке, то вношу изменения в testlib. Видимо,
причина тому — невозможность погрузиться в сложную задачу с большим контекстом по Polygon/Codeforces, но желание сделать
что-то полезное здесь и сейчас.
Напоминаю, что testlib — мощная библиотека и стандард де-факто для подготовки задач по программированию, если
вы используете С++. С помощью testlib можно значительно упростить подготовку: валидаторов, генераторов, чекеров и интеракторов.
Все эти программы ниже буду называть testlib-программами.
<s>Вот <a href="https://testlib.googlecode.com/svn-history/r94/trunk/testlib.h">код ревизии, о которой идет речь</a>.
А вот <a href="https://code.google.com/p/testlib/source/diff?path=/trunk/testlib.h&format=side&r=94&old_path=/trunk/testlib.h&old=62">ссылка с
подсвеченными изменениями</a>, которая может заменить весь текст поста.
Как только будет понятно, что последние изменения финализированы, то ...
Вот код ревизии, о
<https://testlib.googlecode.com/svn-<B>history</B>/r94/trunk/testlib.h>
167.
Codeforces Round #481 (Div. 3) Hello!
[contest:978] will start on [contest_time:978]. It will be the second Div.3 round in the
history of Codeforces. You will be offered 7 problems with expected difficulties to
compose an interesting competition for participants with ratings up to 1600. Probably,
participants from the first division will not be at all interested by this problems.
And for 1600-1899 the problems will be too easy. However, all of you who wish to
take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round,
solutions will be judged on preliminary tests, and after the round it will be
a 12-hour phase of open hacks.
[Remember](/blog/entry/59228) that only the <i>trusted participants of the third
division</i> will be included in the official standings table. As it is written by
link, this is a compulsory measure for combating unsporting behavior. To qualify
as a <i>tr...
[contest:978] will start on [contest_time:978]. It will be the second Div.3
round in thehistory
Announcement of Codeforces Round 481 (Div. 3)
168.
Handle History Happy New Year everyone! Though I am not really happy. Because it seems I'm all alone in codeforces. People who were my friends or whom I followed have worn a mask like Halloween's Eve. I was quite surprised: where the hell prince of Persia has gone, the [kingdom](http://codeforces.com/top-contributed) is rather ruled by a stranger [user:amd,2015-12-31]! It feels so scary around here!?! So, my request to Mike and Mirzayanov is, to move this handle change festival at Halloween's Eve rather than now at such a joyful moment.
OK, Enough introduction, let's get to the point. We need an option(=feature) where the history of handles we used will be kept save. Because, we don't know who is that guy commenting there.
(Most probably, this feature will not be implemented because some guys here change handle to hide their identity. But, that feature will expose them easily.)
Until we get this feature, let's save our handle history manually and publicly in some place: Why not here? You'll me...
Handle History, (=feature) where the history of handles we used will be kept save. Because, we
don't know who is that, OK, Enough introduction, let's get to the point. We need an option(=feature)
where thehistory of, Until we get this feature, let's save our handle history manually and publicly
in some place: Why
169.
CEOI 2018 wrap-up CEOI 2018 is now a part of history!
Task statements, test data, model solutions, translations and some slides with solutions can be found at https://ceoi2018.pl/tasks/
We have two winners of CEOI 2018: Costin-Andrei [user:geniucos,2018-08-18] Oncescu from Romania and Mariusz [user:Mariusz1,2018-08-18] Trela from Poland. Congratulations!
Full scoreboard can be found at https://ceoi2018.pl/results/
The problems were added on Szkopuł and can be solved there (unfortunately, right now only in C/C++): https://szkopul.edu.pl/p/default/problemset_eng/ceoi/2018
We uploaded some photos to our Facebook fanpage: http://fb.com/ceoi2018
And finally, CEOI 2019 will take place in Bratislava, Slovakia!
CEOI 2018 is now a part of history!
170.
Codeforces Beta Round #74 - Short editorial except Div. 1 E <p>Very strange contest. On the one hand - interesting problems, on the other hand - very disbalanced difficulty. To my mind, problem scoring should be the following:</p><div>Div. 1: 1000-1500-1500-1000-???</div><div>Div. 2: 500-500-1500-2000-2000</div><div><br></div><div>That's why I don't very like this contest. But, once again, problems were interesting, thanks to the author!</div><div><br></div><div>Now short editorial.</div><div><br></div><div>Problem A - Cableway (div. 2)</div><div>The only thing in this problem is to write expression for time of the arrival for final group of students of each color. This could be done with the following code:</div><div><div>ans = 30 + 3*((r+1)/2-1);</div><div>if (g) ans = max (ans, 31 + 3*((g+1)/2-1));</div><div>if (b) ans = max (ans, 32 + 3*((b+1)/2-1));</div></div><div><br></div><div>Problem B - African crossword (div. 2)</div><div>Due to the small restrictions, the problem could be solved with the straightforward O(n*m*(n+m)) algo of finding ...
From test 1 it becomes clear that the game process is dependent on history, so
any DP schemes
Tutorial of Codeforces Beta Round 74 (Div. 1 Only)
Tutorial of Codeforces Beta Round 74 (Div. 2 Only)
171.
A series of improvements - don't miss it! <div>Good night everybody. I'm writing this at night, which is why my greeting is such. I would like to present to you several improvements on Codeforces.</div><div><br></div><div>1. Now when you click at the cell of the standings and view the history, you can find a link to its source code. Thus, you have a direct opportunity to view the code of each user for each problem. Of course, the judgement protocol with tests is also available there. At the moment viewing different solutions of one problem by one person is not very convenient - we'll think of something later.[cut]</div><div><br></div><div>2. Now all the finished contests have an open view tests policy. Of course, you should remember about the license while viewing any Codeforces tests :)</div><div><br></div><div>3. The "Presentation Error" verdict is considered outdated, challengingly formalized and useless to anybody. </div><div>We know that nobody whatsoever can say correctly what the difference between the Wrong Answer...
1. Now when you click at the cell of the standings and view the history, you
can find a link
172.
Some Statistics About CF Rating Changes (2018/07 update) #### Overview
There are 1409603 rating changes in 792 rated contests (by 2018/07/14, including those mentioned in the "Something Weird" section). There are 142117 users with at least one rating change. The overall average of deltas is -6.671139.
#### Rating Changes Distribution
<img src="https://image.ibb.co/gZjnpJ/hist.png" width="90%"/>
<img src="https://image.ibb.co/jejnpJ/hist2.png" width="90%"/>
(Well, it looks like a boa constrictor eating an elephant...)
#### Top 20 Events: Positive Rating Change
<table>
<tr>
<th>#</th>
<th>Who</th>
<th>Δ</th>
<th>Rating</th>
<th style="width: 25em;">Contest</th>
</tr>
<tr>
<td>1</td>
<td>[user:Mhammad1,2018-07-16]</td>
<td><span style="color:green;font-weight:bold;">+803</span></td>
<td><span style="font-weight:bold;" class="user-gray">-22</span> → <span style="font-weight:bold;" class="user-gray">781</span></td>
<td>[contest:814]</td>
</tr>
<tr>
<td>2</td>
<td>[user:white_1,2018-07-16]</td>
<td><span style=...
contest pages was 83 higher than those on the user history graph. 6. In
contest pages, ratings less
173.
Problem Parser Contest <p><b>The coding phase has been finished. Please wait for the final testing and results.</b></p><p>
Good day everybody.
</p>
<p>
<i>Everything written below is not a April Fool's joke. Though it is also a funny occasion :)</i>
</p>
<p>
We are glad to announce a new experimental contest on Codeforces, "Problem Parser Contest".
</p>
<p>
Have you ever made training sessions, using the previous contests' archives? Have you downloaded from the Internet contest archives to test for your solutions locally? If the answer is 'yes', then you couldn't help noticing that each organizer insists upon inventing his own way (format) to distribute problems. Yes, it is true!
</p><p>
I've prepared and organized a huge number of trainings based on the previous contests. It is often rather a monotonous task; one often has to write some scripts that rename the input/output files of the problem into the standard form. In archives they are called very differently: they can be river.in.1, r...
automatic. You will really help us and your name will be part of Codeforces's
history of great deeds
174.
PSA: don't feed the trolls! Regarding the recent events, there have been a lot of genuine comments from all sides, and although we may not agree with many of them, they are still someone's legitimate opinions. But there has also been an increase in people who are not saying what they really think. Instead, they are writing deliberately to provoke an emotional response. Most of them are probably doing it for fun, but there is also the chance that some might try to get something out of it.
It is fascinating to me that the internet has had at least 25 years of experience with trolls and everyone still does the one thing they should not do: feeding the trolls. Actually, people seem to be barely familiar with the concept as a whole. The meaning of the word has been diluted a lot due to improper usage. When [user:rotavirus,2022-02-28] was banned, in the discussion that followed, very few people seemed to realize that he did what he did for exactly this purpose.
Let me first reiterate what a troll is. A _troll_ is...
bold and I think false claim; at least in the rest of Europe history books
aren't full of how great
175.
Neural Networks to detect Obfuscation Hi,
[user:MikeMirzayanov,2023-07-26]
Why can't we just write a neural network which learns what obfuscation means and can read through all submissions after training the model, it will automatically flag ppl who are obfuscating?
Isn't trying to hide code or make it hard to read against policy?
The solution seems very simple to me, just make a NN. You already have so much data from past?
If you need more data,
----------------------
make everyone who wants to participate in the next contest (and for each subsequent contest) , be allotted a random submission in history of codeforces. They have to judge if its obfuscation or not. Once its submitted then they can register. People with higher rating will have higher say in whether a submission is really obfuscated. Something like Amazon Mechanical Turk.
Use your loyal coders(however much remaining) to help us clean and purge this community!
(Reading through a code to understand obfuscation doesnt take more than 1-...
allotted a random submission in history of codeforces. They have to judge if
its obfuscation or not
176.
Wikipedia article about Petr Mitrichev is being considered for deletion <img src="http://codeforces.com/userphoto/title/Petr/photo.jpg" style="float: right;width: 150.0px;margin: 0.5em 1.0em;" /> <p>Not so long ago in the English Wikipedia has been added to <a href="http://en.wikipedia.org/wiki/Petr_Mitrichev">the article about Petr Mitrichev</a> ([[user:Petr,2012-01-25]]). Currently, there is a discussion of this article for removal due to the lack of significance. Here is a quote from the discussion: "I don't see how Petr is notable in Wikipedia standards. What makes him different from the hundreds or maybe even thousands of others who are on a similar level as him at competitive programming?".</p> <p>By the way, there is <a href="http://en.wikipedia.org/wiki/Reid_Barton">the article about Reid Barton</a>, the outstanding contestant from US. Who is more valuable for the history?</p> <p>It would be nice if those who is familiar with the rules of Wikipedia, added to the discussion to support Petr.</p> <p>By the way, the article actually seems...
Barton, the outstanding contestant from US. Who is more valuable for the
history?
177.
Algorithms Live! Looking for a Challenge? This week's episode features [user:monsoon,2019-01-09] as a special guest. Tomasz Idziaszek was an ICPC World Finalist from 2005 and a TCO Finalist from 2004-2005. He is an author of over 100 problems, including many hard and interesting problems from Algorithmic Engagements. He was an editor for the polish educational magazine Delta and the famous competitive programming book "Looking for a Challenge?". In 2018 he was a problem setter for the IOI. He also maintains the website [http://www.algonotes.com/](http://www.algonotes.com/) that offers interesting educational materials on advanced algorithms.
In this episode we discuss the history behind "Looking for a Challenge?" and his famous problem Termites ([online judge](https://szkopul.edu.pl/problemset/problem/Wa4p6tM-ZrLBEsLFQF1ZTAZf/site/?key=statement)), which was included in the book. This problem is truly beautiful and I hope many of you will enjoy the [episode](https://www.youtube.com/watch?v=pOv4LRNt0jo).
**Update:** Anyon...
In this episode we discuss the history behind "Looking for a Challenge?" and
his famous problem
178.
Predict: myee will reach 4000000000000000 in 1 year. ## [Origin：](https://codeforces.com/blog/entry/120544)
As we have witnessed, in the recently concluded **myee Round 114514**,[user:myee,2023-09-21] achieved the 0st place.
In fact it was the 114514th time that he got rank#1 in myee: rank#1 in the myee Round 1919810.
This is only what he has achieved on Codeforces; when we examine his achievements in other areas, we can still be surprised.
For example, on the myeeCoder, he has been rank#1 in AmyeeC for 114514000 times yet.
He has been the youngest LGMyee in the history of Codeforces so far. (I means the age when he reached LGMyee. Sorry for the confusion it has made.)
In the ZJOI 2024, he reached rank 1 in Zhijiang, one of the best provinces on CP in China.
In the CNOI 2025, he got 999pts in the 1st place, while the one in the 2nd place got only 0(999pts less than him!), which is amazing.
In the near future, he'll definitely represent China in participating in the IOI.
From ISIJ to APIO, from Codefoces to At...
He has been the youngest LGMyee in the history of Codeforces so far. (I means
the age when he
179.
One more Cheater follows the Karan pathway It has not been long since one of the self boasted guys **Karan**'s cheating was revealed at Codeforces. Looks like this time it one of his disciples who is following the same path. The guy who has been caught red handed is [user:praveenojha33,2020-05-02] who keeps boasting of his programming skills at public groups.
This time, I will present you two new cheaters of the community. One of them is [user:praveenojha33,2020-05-02] and the other is [user:mamme_hunter,2020-05-02]
In yesterday's contest, [user:praveenojha33,2020-05-02] copied all the solutions from [user:mamme_hunter,2020-05-02]. [user:mamme_hunter,2020-05-02] cannot claim that the solutions were copied from ideone or from some other source, since both of them tend to know each other well, and have participated in team contests too. (Check [user:praveenojha33,2020-05-02]'s submission history to clarify).
The doubt came up to my mind when [user:praveenojha33,2020-05-02]'s code appeared clumsy on the first look. So I...
participated in team contests too. (Check [user:praveenojha33,2020-05-02]'s
submissionhistory to clarify).
180.
Congratulations to Moscow SU Red Panda team! ...on being the first team in the history of ICPC that will hold the World Champions title for three consecutive years!
...on being the first team in the history of ICPC that will hold the World
Champions title for
181.
Thank you, MikeMirzayanov! I started coding after discovering about [user:MikeMirzayanov,2022-12-01]'s history in cp and his great **codeforces** platform that inspired me and thousands of competitive programmers all over the world, so to honor him, I made a drawing of him. Thank you MikeMirzayanov for inspiring me to begin learning such an incredible subject and your efforts to keep codeforces a fair environment skipping and banning cheaters.
<a href="https://imgbb.com/"><img src="https://i.ibb.co/V9G9sjp/mikedraw.png" alt="mikedraw" border="0"></a>
PS: please upvote, showing our deepest appreciations for Mike's efforts.
I started coding after discovering about [user:MikeMirzayanov,2022-12-01]'s
history in cp and his
182.
CodeForces Round 61 Well, I finally find time to write yet another blog post.<br><br>My first rated div2 match! :) <br>I really cannot comment my feelings after the match in one sentence.A blog post is surely the best way to express it.<br><br>Firstly, problem A.<br>I began coding in my default language C++ and used strings.I finish coding in less than 2 mins and answering coming for samples 1 and 2.<br>But, WA for sample 3.What the ****?<br><br>I check my code and a quick realisation why I fail.I have to make a quick decision about what to do next.<br>After struggling a little in dilemma, I move to Python.Less than 2 minutes into coding and I make a submit on A.Pretests Passed! Phew!<br>Now, I m like - "I need to get B fast!". One quick glance at the standings and the statistics are sky shooting.<br><br>I dont take into my head.Still calm and contained while reading B.After a quick read into a problem, I feel "Yes!I know this!" :-).<br>Again, few minutes into coding and hurray, another quick submit on B ...
P.S:Do leave your comments.
EDIT:Yayy!A new color!This adds one more to my codeforces history. :)
183.
CSES Range Queries solutions Hey Codeforeces! How are y'all doing? I was solving the CSES Range Queries module and thought of sharing my solutions with you if it's of any use. This blog entry is motivated by [user:kartik8800,2024-04-05]'s own entry ([https://codeforces.com/blog/entry/77128](https://codeforces.com/blog/entry/77128)). I noticed it was missing some of the last problems of the list, so I thought of adding those here as well.
This is my first blog entry, so don't mind to correct me if you notice anything odd in here. If you have any alternative solutions to these problems, it'd be great to share them as well!
Static Range Sum Queries
------------------
Given an array, answer $q \leq 2\cdot10^5$ queries consisting on the sum of values in the subarray $[l, r]$.
Let's obtain the answer of a single query from the precalculated sum of every prefix in the array. This technique is called **prefix sum**. This approach allows us to answer each query in $O(1)$.
<spoiler summary="How to obtain the a...
We can interpret the update history as a split timeline, will follow the update history of the original array and its copy.
184.
Metaverse- Take a leap into the Future Facebook’s decision to rename itself with the new corporate name Meta Platforms Inc. -marked an appropriate endpoint for a year in which the relatively murky concept of the Metaverse became one of the most hyped buzzwords in technology. Many people laughed when Facebook renamed itself, but do you actually know the reason behind it??
Metaverse has set the trend for all internet things so much that it now has its own Wiki definition. Metaverse has already become a part of our lives without us knowing about it. People who play Roblox, Fortnite, Minecraft, etc., are already living in metaverses and won’t likely hesitate to join another where their friends and the things they enjoy all exist.
-History:
Before understanding metaverse, let us go back to when the internet was invented. British computer scientist Tim Berners-Lee published the first website on August 6, 1991. He dreamt of linking together information with hypertext that could be viewed via a web browser. Years later, he c...
-History:
185.
(Free) Websites to test and to improve typing speed/accuracy #### 1.Typeracer
**Typeracer** is a game of competition that drives your desire to type faster to beat the opponents. The quicker the keys are stroked, the faster your car moves along the track. Essentially, whoever finished the paragraph first has the fastest moving car and will win the game.
Play with random users, a friend, or on your own for practice. Create an account before you begin to save your scores on the leaderboard and see how you compare to the other users.
#### 2.Monkeytype
**Monkeytype** is a minimalistic and customizable typing test. It features many test modes, an account system to save your typing speed history, and user-configurable features such as themes, sounds, a smooth caret, and more. Monkeytype attempts to emulate the experience of natural typing during a typing test, by unobtrusively presenting the text prompts and displaying typed characters in-place, providing straightforwa...
account system to save your typing speed history, and user-configurable
features such as themes, sounds
186.
Modular exponentiation with rEaLlY big exponents [problem:17D] my submission history is embarrassing
Doing a number theory tour right now haha, this problem just wants you to compute $(b-1)\cdot b^{n-1} \bmod c$.
Intuitively, I tried to use a simple repeated squaring technique, but always got TL around test case 27 (in which b and c are around 10k digits). I thought python's builtin integer implementation was to blame, and some fiddling shows that python's Decimal module has a pretty slow division (they don't optimize for integers), so I switched to Java's BigInteger, which still is slow. Then it came to me the repeated squaring approach is O(L^2) where L is length of the exponent, not L*log(L) as I initially thought. No wonder it failed then because b and n can be 10^6 digits. On the good side, c is not so large, so Euler's totient theorem can help: just replace n-1 with $n-1 \bmod \phi(c)$. (You can compute the remainder of a large string modulo a fairly small number by going over its digits RTL, keeping track of the remainde...
[problem:17D] my submission history is embarrassing
187.
The Ten Eternal Truths of Competitive Programmers 1. A Competitive Programmer places their fellow programmers above all and makes any and all sacrifices necessary to further the cause of competitive programming and the advancement of our people.
2. A Competitive Programmer does all they can to secure the existence of our people and a future for programming.
3. A Competitive Programmer takes pride in the history, cultures, values, morals, and accomplishments of their people and live by those standards set by our ancestors.
4. A Competitive Programmer strives to exemplify class, strong character, and a standard of excellence at all times so that they never let their people down.
5. A Competitive Programmer cultivates camaraderie and fosters unity amongst our people for we will triumph together as one or we shall perish alone.
6. A Competitive Programmer thinks before they act so that they do not bring shame, harm, or disgrace to their self or our people.
7. A Competitive Programmer strengthens their body through health...
3. A Competitive Programmer takes pride in the history, cultures, values,
morals, and
188.
To be a master before it became mainstream Hello, Codeforces!
I think, today I become the first master in history. Statistics say that I had done it before the majority of users were born.
Thanks to [user:MikeMirzayanov,2020-07-25] for excellent Codeforces and Polygon platform!
P.S. I don't know, how does it work and I haven't done anything to achieve that. But I have explored that this bug is only on i-servers (i1, i2, i3).
I think, today I become the first master in history. Statistics say that I had
done it before the
189.
Unable to view complete user submission history on SPOJ Hello Codeforces community,
I resumed solving SPOJ problems a week or so back. I have noticed that you're no longer able to view the complete user submission history (either normally or via signed list) for any user apart from yourself. This is an impediment. I personally look up to a few users and solve problems that they're solving( I'm sure there are many others like me) and also see what order the top/popular users have solved the problems in, this also spares me the trouble of spending time on finding good/challenging problems on SPOJ.
I kindly request "top" users of SPOJ or just about anyone who has done a lot of SPOJ (a lot of means arbitrary lets just put 300-400+) and benefited from it to "try" and post their submission history (You could put your own signed list in a text file and host it on pastebin). It would be extremely helpful for newbie coders and for anyone who does a lot of SPOJ by following what other solve.
Thanks.
P.S. I have also sent a mail to SPOJ expl...
Unable to view complete user submission history on SPOJ, means arbitrary lets just put 300-400+) and benefited from it to "try" and
post their submissionhistory, you're no longer able to view the complete user submission history (either
normally or via signed
190.
masterpiece.txt Bee Movie Script
According to all known laws
of aviation,
there is no way a bee
should be able to fly.
Its wings are too small to get
its fat little body off the ground.
The bee, of course, flies anyway
because bees don't care
what humans think is impossible.
Yellow, black. Yellow, black.
Yellow, black. Yellow, black.
Ooh, black and yellow!
Let's shake it up a little.
Barry! Breakfast is ready!
Ooming!
Hang on a second.
Hello?
- Barry?
- Adam?
- Oan you believe this is happening?
- I can't. I'll pick you up.
Looking sharp.
Use the stairs. Your father
paid good money for those.
Sorry. I'm excited.
Here's the graduate.
We're very proud of you, son.
A perfect report card, all B's.
Very proud.
Ma! I got a thing going here.
- You got lint on your fuzz.
- Ow! That's me!
- Wave to us! We'll be in row 118,000.
- Bye!
Ba...
Are we going to be bees, orjust Museum of Natural History keychains?, where the world anxiously waits, because for the first time in history,
191.
Feature Request: Contests history filter I think, it would be helpful to have a filter on the contests history page. For example, filter by division, by a taking part and by duration. Like it has been implemented for the gyms page. It may help to find unsolved div. 2 only contests or special rounds.
Picture to attract your attention.
**UPD0** Maybe add order of sorting.
Feature Request: Contests history filter, I think, it would be helpful to have a filter on the contests history page. For
example, filter by
192.
Blog post history Today i stumbled upon [this post](http://codeforces.com/blog/entry/15389). In this case, judging from comments, I can guess the original contents of the post fairly well. However, the general idea got me thinking — why all the history of comments is preserved, while the history of posts themselves — don't?
Blog post history, got me thinking — why all the history of comments is preserved, while the
history of posts
193.
Codeforces Viewer Hello guys, as a coding challenge in lockdown, I have created a website for Codeforces problem set viewing. Its primary function is to filter problems in problems-set based on some parameters like the difficulty of the problem, rating min, rating max, tags, etc. It has some other functions also like a link to other users attempted but unsolved problems, random problem suggestor based on your rating, etc. I hope everyone likes it. CFViewer is my first web development project.
**Link**: [rudradesai.in/cfviewer](https://rudradesai.in/cfviewer)
Also if you feel like any functionality is missing, then please write it to me on [[email protected]](mailto:[email protected])
Any feedback, positive or negative, is welcome. Thank You!!
Update 1: Added new functionalities, now you can try a random unattempted contest, see all the contest on code forces with an added feature of attempted or not. Also, you can view submissions and problems for each attempted contest.
And o...
will suggest problems and contests based on your submissions history. Also, it
will suggest filters for
194.
Cheaters found in CF Round #660 , #658 and #657 I found these two cheaters in Yesterday's contest ([ Codeforces Round #660 (Div. 2) ](https://codeforces.com/contest/1388)). They are from from the **same institute** (Jaypee Institute of Information Technology, Noida). They have been doing this in all almost **every past contests** they both participated. CF authorities should atleast **disqualify them from Round #657** , as they have gained positive deltas from that round unlike other rounds where they have dropped.
User 1: _**Agraj Garg**_ [agrajgarg](https://codeforces.com/profile/agrajgarg)
User 2: _**Vatsal Agarwal**_ [Warhead38](https://codeforces.com/profile/Warhead38)
Submissions(For CF Round #660):
A: [88462008](http://codeforces.com/contest/1388/submission/88462008) by Agraj and [88463088](http://codeforces.com/contest/1388/submission/88463088) by Vatsal (Apparently Vatsal has also submitted two absurd solutions to fool the authorities )
B: [88479313](http://codeforces.com/conte...
contest history of [ _**Vatsal**_
](http://codeforces.com/contests/with/Warhead38) and [ _**Agraj
195.
About Offensive Comments/Blogs ### Whats Happening?
Recently a bunch of comments have been popping up about certain political/religious topics on blogs that are in no way related to the blog's topic.
And some users with offensive usernames have been commenting and making blogs that are straight up disrespectful, cracking up fights in the blog's comments in the process.
For that reason I want to propose a few ideas on how we can reduce and maybe completely get rid of these users since Codeforces as a platform has been growing fast recently with tons of new users registering.
### What Can We Do?
I have some ideas that might help.
#### IDEA 1 :
Offensive comments/blogs could have certain warnings asking the user to downvote and report the certain comment/blog if it is indeed offensive or disrespectful.
(maybe certain words detected in the blog could be a reason to issue this warning, or just history of user)
#### IDEA 2 :
Authors could clean up and moderate their blogs by hiding comments and mo...
detected in the blog could be a reason to issue this warning, or just history
of user)
196.
Comments improvements I'm glad to announce two new features. Both improvements have repeatedly appeared in discussions on our pages.
<div><ul><li>Now, new comments for you (of course, you must be logged into the system) painted with "sky blue" color. A comment is considered a new five minutes, as you saw it the first time (first view of the post does not count).</li>
<li>You may edit your comments. You may use it to change the spelling or grammatical errors, formatting or to do minor fixes. Changing the meaning of a comment is unacceptable. Comments history have navigation to-the-past-and-back, or more precisely to-left-and-right. </li>
</ul>
I hope that now the discussion on Codeforces become more comfortable. <span class="Apple-style-span" style="border-collapse: collapse; font-family: verdana, arial, sans-serif; font-size: 13px; "><a href="http://codeforces.com/profile/ivan.popelyshev" class="rated-user user-red" style="font-family: arial; text-decoration: none !important; font...
, formatting or to do minor fixes. Changing the meaning of a comment is
unacceptable. Commentshistory
197.
All time-cheating Record broken! <a href="https://ibb.co/5s34X3z"><img src="https://i.ibb.co/gt89b8X/lol.jpg" alt="lol" border="0"></a>
Bruhh WTF! 12 skips in total? **Again cheating in the last educative round 141 **C**** and thankfully the plagiarism system became smarter as it spotted you immediately [submission:190392625]?
Tell me, do EDU rounds involve **room-code locking**, that you brainlessly complain of as being the reason for your div2 skips, you are even an idiot who doesn't know how things work. In div2, the first to submit the code is **NOT** skipped, so your claims are utter shit as you.
You had been skipped 4 times (Two Automatic by the plag check system ,and 2 Manual by [user:MikeMirzayanov,2023-01-25] or moderators)
**Are you brain-crippled?** [user:mhmd_bakr,2023-01-25] I thought my blogs taught u something! You can't do competitive programming and you can't even cheat lol! Please, go do some other shit. I think competitive programming is not for you and your cheater friends!
Finally, le...
Finally, let me here put your dirty cheating history. Thanks
[user:redc,2023-01-25], Some Osint
198.
ACM-ICPC Asia-Amritapuri Onsite Mirror Contest 2015 on CodeChef For the first time in the history of Indian ACM ICPC, a mirror contest will be hosted on CodeChef for Amritapuri regionals at <a target="_blank" href="http://www.codechef.com/AMR15MOS">http://www.codechef.com/AMR15MOS</a>.
<b>Time</b>: 21st December 2015 (1000 hrs) to (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your <a target="_blank" href=http://www.timeanddate.com/worldclock/fixedtime.html?msg=ACM-ICPC+Asia-Amritapuri+Onsite+Mirror+Contest+2015&iso=20151221T10&p1=44&ah=5>Time zone</a>.
<br />
<b>Details</b>: <a target="_blank" href="http://www.codechef.com/AMR15MOS/">http://www.codechef.com/AMR15MOS/</a>
<br />
<b>
Registration</b>: It will be a team contest. You need to register your team <a target="_blank" href=" https://www.codechef.com/teams/register/AMR15MOS/">here</a>
New users please register <a target="_blank" href="http://www.codechef.com/user/register/">here</a>
<br />
</p>
The contest is open for all and those, who are intereste...
For the first time in the history of Indian ACM ICPC, a mirror contest will be
hosted on CodeChef
199.
Square869120Contest #5 in AtCoder [Square869120Contest #5](https://s8pc-5.contest.atcoder.jp/) will be held on [Sunday, April 15th, 20:00 JST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20180415T2000&p1=248).<br />
<br />
**About Square869120Contest**<br />
<ul>
<li>This contest is unofficial.</li>
<li>Square869120Contest has been held 4 times before, and this is the 5-th contest of Square869120Contest.</li>
<li>From the 3-rd contest, **both Engish and Japanese statements are prepared.**</li>
</ul>
<br />
**Contest Information**<br />
<ul>
<li>Time: [Sunday, April 15th, 20:00 JST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20180415T2000&p1=248)</li>
<li>Duration: 240 minutes</li>
<li>Tasks: 9 (Consists of 8 algorithm tasks, 1 marathon task)</li>
<li>Writer: [user:E869120,2018-04-10], [user:square1001,2018-04-10]</li>
<li>Rated: No (unrated)</li>
<li><b>The first problem is as easy as Codeforces Div2 A, and the last problem is as hard as Codeforces Div1-D,E problems. In addi...
unrated contest which have a long history. There's 4 previous contest, so you
can solve them to
200.
A bug about hacking I think I found a bug about hacking. I did 2 successful hacks during Codeforces Round #115, but after contest it showed there's only one hack. The other one is 'ignored'.
But I think it should be a successful hack.
My hack:
**38336 Apr 14, 2012 1:25:35 PM sillycross Skyly A --- Robot Bicorn Attack Ignored**
The victim's submission history:
**00:13:50 Accepted [pretests] → 1532327**
**01:39:54 Accepted [final tests] → 1535677**
And submission 1532327's status
**By Skyly, contest: Codeforces Round #115, problem: (A) Robot Bicorn Attack, Hacked, #**
Obviously the submission done in 00:13:50 was hacked by me ( I'm the only one who hacked this solution ) . But the hack was ignored.
I think it was caused by my another hack using the same input.
**38343 Apr 14, 2012 1:30:08 PM sillycross helThazar A --- Robot Bicorn Attack Successful hacking attempt**
I knew that the codeforces judge would ignore same hacking inputs and only keep the last o...
The victim's submission history:
201.
Competitive programming on Wikipedia <p>Friends, Colleagues and Comrades!<br /><br />Today we found that wikipedia lacks an article on Competitive Programming - our beloved branch of sports and engineering.<br /><br />We are to fix it.<br /><br />I wrote very short stub page <a href="http://en.wikipedia.org/wiki/Competitive_programming">here</a>. But my English is poor and my knowledge of Competitive Programming facts and history is not great. Also I do not know wikipedia rules very well (though I like this resource, as many of you).<br /><br />Please help to improve it. You may edit an article itself, or write to me useful links on the subject or proposition on what to add/improve here.</p><p><b>UPD:</b> Thanks to unknown colleagues who significantly improved existing four paragraphs. Now I want to add another two: sample of the problem statement and list of some most notable contestants.</p><p>For first I need the allowance of someone of the authors to post some nice, easy to understand and, possibly, funny problem. For...
>. But my English is poor and my knowledge of Competitive Programming facts and
history is not great
202.
Codeforces WatchR 2.0.0 (Frost): Filter problems by tags & complexity Hello, Codeforces! The past two months we were busy migrating the rest of our application to our own backend, which allows us to implement even more cool features. Download the latest [Codeforces WatchR](https://github.com/xorum-io/codeforces_watcher) app in [Google Play](https://play.google.com/store/apps/details?id=com.bogdan.codeforceswatcher) and [App Store](https://apps.apple.com/app/codeforces-watchr-contests/id1495591299).
Now when the lists of contests and problems are coming from our backend, we can fetch them in the mobile apps much faster and in a more robust way. Also, it allowed us to easily implement the long-awaited feature of filtering problems by tags and complexity.
Future plans
-----------------------------------
We did a long preparatory work to cover the most used features of the Codeforces in our mobile app. Now we are ready for the next leap with big unique features, which you wi...
/Robert_Frost), which is the only poet in history to get FOUR (4!) Pulitzer
Prizes for Poetry (kind
203.
[Mac Tutorial] Setting Up GNU's C++ Compiler on MacOS Hello everyone!
I believe many MacOS users have encountered this problem (and it has been lasting for the entire history of programming) so I decided to post a blog to <strike>gain free contributions</strike> help them install GNU's GCC. GCC has many useful libraries that Clang (Mac's default c++ compiler) doesn't have. Such as the classic `<bits/stdc++.h>` and also the [Policy Based Data Structures](https://codeforces.com/blog/entry/11080).
<spoiler summary="Blog Lore">
Today I saw a CSES problem that needed the indexed tree from pb_ds, so I started trying to get GCC, and it finally worked! After solving this problem, I decided to make this blog.
</spoiler>
<hr>
SO let's get to the tutorial. Have `Terminal.app` opened up because we will be typing a lot of commands.
Type `cd ~` in the Terminal and press enter, this makes the computer go to the root folder. I will assume that your Terminal is always in the root folder for this tutorial.
By the way, any time you think...
history of programming) so I decided to post a blog to gain free contributions
help
204.
deltixlab’s interview: Deltix rounds back story _I am very glad to introduce my guests from [Deltix](https://deltix.io):_
_Aliaksandr [user:sdryapko,2021-12-10] Drapko, the Head of Technology of [CryptoCortex](https://deltix.io/products/cryptocortex.html) product and_
_Vladislav [user:Vladik,2021-12-10] Vishnevsky, the coordinator of all competitive programming activities by Deltix and the key developer of [MarketMaker](https://deltix.io/products/marketmaker.html) product._
_I am proud to be their compatriot, so let me start with some belorussian words of greetings_
_- Прывiтанне, Аляксандр і Уладзіслаў!_
- Прывiтанне, Наталля!
_- Deltix is the sponsor of the Belarus National School Olympiad in Informatics. Last spring you represented Deltix at the National Final award ceremony. The award ceremony was very touching for the winners. But what about you? How did you feel presenting them prizes? What were you thinking about at this moment?_
.<br>
### History:<br>
A bit about its history, It was developed by a British computer scientist Tony Hoare (Not that it helps in understanding the algorithm)<br>
#### Application / Where to use Quick Sort:<br>
There are many sorting algorithms then why do we need to learn/ use quick-sort? Quick sort is used in places where we need to efficiently sort the elements. It is also used when there are restrictions in space availability.<br>
#### What is the time complexity of quick sort:<br>
Quick sort has an average time complexity of O(n log n) but if we don't chose the pivot correctly, the worst case time complexity is O(n^2).
#### How Quick Sort works:<br>
Quick sort can be related in the real life like this. Suppose a student comes to a teacher and asks her to tell the student s who are better than him and the ones who are weaker than him. Now the teacher looks at the class in the order they are sitting, and for each stude...
Quick Sort is a sorting algorithm (duh).
### History:
A bit about its history, It was
206.
Mail.Ru Cup 18 Experience (2nd contest on CF) So I actually planned on this one being my 3rd contest, but
last week, I tried to participate in a contest that took place 3am in my time zone.
I was practicing, trying to stay up for the contest, but fell asleep.
Next time, I'm either going to stay awake or not plan to attend a contest at those hours.
Anyways, solved 1, better than solving 0 like in my first contest.
So one of two things are true, either I am far more capable than contest result history indicates or I am extremely delusional.
I was definitely extremely nervous, and had "butterflies" in my stomach.
Here's the one and only reason I love competitive programming:
I used to box seriously when I was 20, and I get more of an adrenaline rush while participating in these contests than
while I am fighting in the ring.
So much FUN!
Oh and one last thing, whatever I do in programming, I made up my mind that the next goal in my plan is to master dynamic programming.
To every other participants of Mail.Ru C...
, either I am far more capable than contest result history indicates or I am
extremely delusional.
207.
A Dissertation on Why CodeForces Should Adopt Communism There comes a time when it becomes necessary for the people to overthrow the existing government. The history of CodeForces has been nothing but a history of class struggle, where the Burgeois oppress the common people. Thus We, the people of CodeForces, must rise up against tyranny. In Order to form a more equal Union, Establish Justice, insure domestic Tranquility, and uphold fundamental Human Rights.
I propose, at once, to **Abolish Rating!** Since the birth of CodeForces, its creators have sewed seeds of injustice into its very foundation. Look no further than the community upvote system. The votes of the Burgeois, such as a grandmaster, counts numerous times more than a newbie. Is this but not an outrageous manifestation of inequality!? Where, the people, or the majority, are silenced by the elite minority and forbidden to voice their opinions. Besides systemic oppression, Ratism as a social norm has completely infested our community. The upper class has pitted the common peopl...
. The history of CodeForces has been nothing but a history of class struggle,
where the Burgeois
208.
CF Suggestion: See past contests in the contests tab ### Viewing Past Contests
It would be really nice to be able to see past CF contests in the Contests tab. Usually they show up below the upcoming contests, but since the ICPC Practice is running for like 2 days straight, we can't see them.
For me it is just an annoying inconvenience because I can get there through my submission history. But if I wanted to VP a previous round for instance, there isn't really a good way of doing that without a link (or if there is a good way, I don't think it is very clear what that way is).
### Possible Solutions
For long contests (ICPC Challenge, Microsoft Q#..., et cetera), it would be nice to still be able to see old contests in the contests list. I can understand if it would be too much of a server load for CF rounds, but these contests likely have much lower participation and are less demanding.
For me it is just an annoying inconvenience because I can get there through my
submissionhistory
Codeforces (c) Copyright 2010-2024 Mike Mirzayanov
The only programming contests Web 2.0 platform
Server time: Apr/24/2024 01:08:05 (k2).
Desktop version, switch to mobile version.
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