Educational Codeforces Round 101 [Rated for Div. 2] Hello Codeforces! On [contest_time:1469] [contest:1469] will start. Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>. This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally. You will be given **6 or 7 problems** and **2 hours** to solve them. The problems were invented and prepared by Roman [user:Roms,2020-12-27] Glazov, Adilbek [user:adedalic,2020-12-27] Dalabaev, Vladimir [user:vovuh,2020-12-27] Petrov, Ivan [us...

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Educational Codeforces Round 61 [Rated for Div. 2]  Hello Codeforces! On [contest_time:1132] [contest:1132] will start. This round is organised in collaboration with Hello Muscat Programming Bootcamp and supported by Sberbank, General Partner of the boot camp and one of the largest banking leaders of Eastern Europe, providing thousands of jobs and innovation in the financial industry. As the Hello Muscat Programming Bootcamp’s General Partner, Sberbank made it possible for students from some of the world’s top universities to attend the bootcamp, by sponsoring their participation. This includes students from Saint-Petersburg State University, Moscow Institute of Physics and Technology (MIPT), Penza State University, National Research Mordovia State University; MRSU, ITMO, Higher School of Economics / Moscow, Volgograd State Technical University, Lobachevsky State University of Nizhni Novgorod, Moscow Aviation Institute, Tyumen industrial University, University of Haifa, Northern (Arctic...

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Contests hack statistics (Number of hacks by round) Just felt like gathering some data about hacks. Parsed around ~400 last contests Probably it would be worth it to also include SFT, but whatever Educational 96 is not finished yet but also whatever Last 100 ------------------ **847** Educational Codeforces Round 96 (Rated for Div. 2) **30** Codeforces Global Round 11 **248** Codeforces Round #674 (Div. 3) **0** 2020 ICPC, COMPFEST 12, Indonesia Multi-Provincial Contest (Unrated, Online Mirror, ICPC Rules, Teams Preferred) **97** Bubble Cup 13 &mdash; Finals [Online Mirror, unrated, Div. 2] **86** Bubble Cup 13 &mdash; Finals [Online Mirror, unrated, Div. 1] **20** Codeforces Round #675 (Div. 2) **1** Codeforces Round #672 (Div. 2) **70** Codeforces Round #671 (Div. 2) **58** Educational Codeforces Round 95 (Rated for Div. 2) **3** Codeforces Round #673 (Div. 2) **11** Codeforces Round #673 (Div. 1) **73** Codeforces Round #667 (Div. 3) **121** Grakn Forces 2020 **4** Co...

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Codeforces Round #321 (Div. 2) Good day to everybody! The next round for the participants of the second division will be held at [September 22, 2015 at 19:30 MSK](http://goo.gl/s6jiwF). Traditionally, the members of the first division may take part in the contest out of competition. I (Vladislav Vishnevski) and [user:igdor99,2015-09-21](Igor Doroshev) are the authors of the round. We would like to please [user:Zlobober,2015-09-21] (Maxim Akhmedov) for the assistance in the preparation of tasks, [user:Delinur,2015-09-21](Maria Belova) for translating statements into English, [user:MikeMirzayanov,2015-09-21](Mike Mirzayanov) for remarkable systems Codeforces and Polygon, as well as our friends [user:Dmitry_Aksenik,2015-09-21](Dmitry Aksenik) and [user:RevtIvan,2015-09-21](Ivan Revt) for their assistance in the round preparation. This is our first round, and, we hope, it won't be the last one! You will be proposed 5 tasks and 2 hours for their solution. The protagonist of the round is the parrot Kefa, who l...

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Topics Problems Good Day to you! While a lot of us, when he begins to start competitive programming he found difficult to found problems on some topics in the beginning to practice of it, and same thing for a lot of ICPC Communites that they have started. These are some topic not advanced and videos, problems and articles on them. <br> <spoiler summary="Prefix Sum & Frequency Array"> [Wonderful Coloring](https://codeforces.com/contest/1551/problem/B1) [Do Not Be Distracted](https://codeforces.com/contest/1520/problem/A) [Letter](https://codeforces.com/problemset/problem/43/B) [Pangram](https://codeforces.com/problemset/problem/520/A) [Andryusha and Socks](https://codeforces.com/contest/782/problem/A) [Count Numbers](https://codeforces.com/group/c3FDl9EUi9/contest/262795/problem/A) [Count Characters](https://codeforces.com/group/c3FDl9EUi9/contest/262795/problem/B) [Range Sum Query](https://codeforces.com/group/c3FDl9EUi9/contest/262795/problem/E) [Count a's](https...

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Codeforces Round #321 Editorial [problem:580A] Note, that if the array has two intersecting continuous non-decreasing subsequence, they can be combined into one. Therefore, you can just pass the array from left to right. If the current subsequence can be continued using the $i$-th element, then we do it, otherwise we start a new one. The answer is the maximum subsequence of all the found ones. Asymptotics &mdash; $O(n)$. [Solution](http://ideone.com/dIGhiB) [problem:580B] At first we sort all friends in money ascending order. Now the answer is some array subsegment. Next, we use the method of two pointers for finding the required subsegment. Asymptotics &mdash; $O(n$ $log$ $n)$. [Solution](http://ideone.com/k4Hlxv) [problem:580C] Let's go down the tree from the root, supporting additional parameter $k$ &mdash; the number of vertices in a row met with cats. If $k$ exceeds $m$, then leave. Then the answer is the number of leaves, which we were able to reach. Asymptotics &mdash; $O(n)$. ...

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My winning theory in IOI 2018 & 2019 — Why I won 2 golds in IOI Dear Codeforces community.<br /> According to [IOI 2019 Results](http://stats.ioinformatics.org/results/2019), I got the 25th place and got successful gold medals twice in a row.<br /> Although it was pretty close to the gold-medal border (only 6.14pts / 600 difference) and it was lower performance than IOI 2018, which I participated when I was orange in Codeforces, I had many chances to get more points in this IOI, even for top 10. Since there are not so many people who have got two gold medals in IOI (and there were many requests like "I want [user:E869120,2019-08-14] to talk about how to get gold in IOI" like [this comment](https://codeforces.com/blog/entry/66909?#comment-510127) and [this comment](https://codeforces.com/blog/entry/66909?#comment-513129)). I want to write something about IOI, which may be useful for people who will participate in IOI next year and also some years later.<br /> <br /> <br /> ### A. First of all At...

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Codeforces Global Rounds 2021: Final Results (GR13-GR18) Tomorrow will be the first global round of this year. And we are happy to sum up the results of last season. We announce the results! We remind you that the global rounds are a joint initiative of XTX and Codeforces. We are happy to announce that they continue into the new year. We hold 6 such rounds per year. All of them are open to both divisions. At each such round, 50 brand T-shirts were handed out, and we are happy to give T-shirts to all problem authors. The prizes for the 6-round series are: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest. - The best 20 participants over all series get sweatshirts and place certificates. The final standings after six rounds (sorted by total points in four best placed rounds): | Place | Contestant | = | GR 13 | GR 14 | GR 15 | GR 16 | GR 17 | GR 18| |--...

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Codechef September Cook-off clashing with Codeforces round 321 Could we change the time of the event please? There are a large number of us who do both of them. This is the first time I see a clash. I posted a similar post in codechef as well: https://discuss.codechef.com/questions/75130/september-cook-off-clashing-with-codeforces-round-321 But Codechef has been hosting the cookoff at the same time for the last few years. It doesn't make sense for them to change it.

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Cheating Ring Invitation Email I got this email some hours ago : Title : Codeforces , From : Penny Zhang <[email protected]> _Hello all,_ __ _If you're interested in exchanging solutions to Codeforces (and maybe even TopCoder) problems in-contest, reply to let me know and I'll explain the system in more detail. The main goal of the system is to prevent leeching (receiving solutions, but not giving), and to prevent detection (altering code). I'm expecting a final ring of size 4-8. I suggest you make a new email account for this to maintain anonymity; use a proxy if you want to take it a step farther. Ideally, no one in the ring should know a single other person._ __ _Quick note: This setup will not be ready by the next contest, which is in less than 12 hours. I hope to be ready for round 321 (in several days), though._ __ _Again, reply with "I'm interested" using an alternate email account (preferably), and I'll include you in a group email._ __ _Thank you all,_ _pzhang_ ...........................

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Statistics of Problems on Div 1 & Div 2 contests I made statistics of the rating and tags of problems based on their in-contest letter assignment (A, B, C, etc.) using the Codeforces API. What I took into consideration ------------------ First of all, only problems taken from contests labeled with Div. 1 or Div. 2 were taken into consideration (I say labeled because I only checked if the division string existed in the contest name). Contests that were labeled Div. 3 or didn't have a listed division (Global Rounds, for example) were not used. Div. 1 problems are offset by the Div. 2 problems. What I mean by this is usually, the Div. 2 C is the Div. 1 A, and in these statistics, I represented them like the former so that I wouldn't get Div. 1 A ratings mixed with Div. 2 A ratings because, well, that would be bad and it was easier lol (the API did it for me). Only problems representable up to H were used, because the later ones were too scarce (and quite frankly, odd in terms of ratings). Possible Sources of Error -------------...

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Problem Topics Good Day to you! I've been asked to make some topic-wise list of problems I've solved. Even though I couldn't involve all problems, I've tried to involve at least "few" problems at each topic I thought up (I'm sorry if I forgot about something "easy"). I've alredy made such list once anyway I've tried to include more problems now &mdash; so here it is: <spoiler summary="aho"> http://www.spoj.com/problems/ADAJOBS/ URI 2226 (5) //[NICE][NUMBERS][DP] http://www.spoj.com/problems/SUB_PROB/en/ http://codeforces.com/contest/696/problem/D 8 http://www.spoj.com/problems/AHOCUR/ 5 //Aho-Corassic + DP https://www.codechef.com/problems/LYRC (5) //Sample aho-brute-force http://codeforces.com/problemset/problem/346/B //Proposed by [user:bradyawn,2019-08-03] </spoiler> <spoiler summary="automat"> 6861 [LA] //CYK UVA 10679 //Suffix Automat http://www.spoj.com/problems/STRMATCH/ //Suffix Automat &mdash; trie might do too http://www.spoj.com/problems/NSUBST...

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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...

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