About the Universal Cup, the Semifinals, and myself... Hey'all! This gonna be a long post, so let me put an important TLDR here first: we are going to host **The 3rd Universal Cup Semifinals**, which will take place on August 24, 2025 **online**, at [11:00 (UTC)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=The+3rd+Universal+Cup+Semifinals&iso=20250824T19&p1=33&ah=5). This contest will be a part of our Finals Team Selection, which the detailed rules and announcements will be published later next week. --- Now for some extra context, if you're interested. Last week, we hosted the [last online stage](https://mirror.codeforces.com/blog/entry/143954) of The 3rd Universal Cup. After that, I posted a [feedback form](https://docs.google.com/forms/d/1g5Txhiirh_lRsvGfkYWRozu0WDDGK31IAXjB7VgeVoM/edit) on our discord server. I received lots of thoughtful responses (P.S — it's still open, so feel free to fill it out if you haven't yet!). I've read through all the feedback, and I'd like to share a few thoughts. ### On the Number...

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InfO(1) Cup 2018 Hello everyone! I'm happy to invite you to take part in the [second edition of InfO(1) Cup](http://info1cup.com/), an online contest meant to be similar to international olympiads such as IOI, CEOI, BOI, APIO, etc. If you remember last year's entry about the contest, you should notice that we've been talking about making it an onsite event, but we decided it's both easier (especially financially) and helpful to more people (as we can have more online participants) to have it online. The contest consists of 2 rounds: the national round and the international round. Participation in both rounds is invitation based (you can see the "official" participants [here](http://info1cup.com/participants)). We've tried to reach out to the official organizers of Informatics Olympiad in several countries to make the competition as fierce as possible by having future IOI-participans, as well as to help those students in their training for upcoming international olympiads. Both rounds will ha...

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Invitation to new OI style contest Info(1) Cup Hello everyone! I'm writing this entry to invite you all to take part in [the first edition of Info (1) Cup contest](http://info1cup.com/). It is an individual contest with algorithmic tasks and we will accept only C++ sources. The contest itself has 2 parts, both of which held online. **You can still take part in the online mirror in any frame of 5 hours before [time](https://www.timeanddate.com/countdown/generic?iso=20170412T15&p0=5121&msg=infO%281%29+Cup+International+Round+-+Online+Mirror+END&font=cursive&csz=1). We invite you all to participate. The tasks should be challenging for everyone The [live scoreboard](http://open.info1cup.com:8890/Ranking.html) of the online mirror is on.** PS: As in all the other contests that have online mirrors, I kindly ask you not to discuss the tasks until all the rounds and their online mirrors end. After that, on the official site, you'll find the editorials of the problems. The first one consists of a national contest in which only ...

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Meta Hacker Cup 2023 Round 1 Meta Hacker Cup Round 1 ================== Good morning! [Meta Hacker Cup Round 1](https://www.facebook.com/codingcompetitions/hacker-cup/2023/round-1) starts on [Saturday, October 7th at 10:00 AM Pacific](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Meta+Hacker+Cup+2023+Round+1&iso=20231007T10&p1=234&ah=3) in under 48 hours! Anyone can register for Round 1 this year, even if you haven't participated in the practice round. Important info: - To qualify for Round 2, you must solve at least one problem in this round. (Due to having too many submissions in the early part of the contest, we relaxed this requirement from the earlier one of needing to place in the top 5000 of the round) - The contest will be **3 hours**. - As usual, you may not discuss solution ideas or code until after the contest hours is over. It's your responsibility to make sure that your code is not leaked. We'll DQ contestants if we have reason to believe they shared code or solutions with oth...

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Story about a certain interactive problem Some time ago, I was part of the scientific committee at [infO(1)Cup](https://info1cup.com/). While discussing problems with other members of the committee I proposed the following problem: _You have to play a game against the interactor on a $N$ by $M$ matrix. Initially all cells are unclaimed. You and the interactor, alternatively, take turns claiming a non-empty set of unclaimed cells. The set of cells chosen in a turn has to be able to fit in a $K$ by $K$ bounding box without being rotated and has to be connected. (There exists a path between any two cells in the set passing only through cells in the set, we define a path as a sequence of cells such that any two consecutive cells have a common side). You can choose whether to play first or second._ Before I discuss the solution to the above problem, I first wish to show you a similar puzzle known in the folklore as _"The round table coin game"_ or as _"The faustian round table coin game"_ . The puzzle goes as follows: ...

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2026 OIs: Everything we know so far Hi! Like last year, I decided to make a blog with all the information we know about the 2026 OIs. Note that text in *italics* is unofficial. Like last time, please share the info you know (websites, locations, dates etc.) in the comments. Thanks in advance to everyone who contributes! --- # International ### IOI 2026 🇺🇿 **Location:** Tashkent, Uzbekistan **Dates:** August 9-16, 2026 **Official site:** https://ioi2026.uz/ ### IIOT 2026 🇷🇴 **Location:** Neamț, Romania **Dates:** May 23-28, 2026 **Schedule:** https://iio.team/schedule/ ### IATI 2026 🇧🇬 **Location:** *Burgas, Bulgaria* **Dates:** *April 15-19, 2026* ## Junior ### InfO(1)Cup 2026 🌐 **Location:** Online **Dates:** February 6-15, 2026 **Official site:** https://info1cup.com/ --- # Europe ### EGOI 2026 🇮🇹 **Location:** Cesenatico, Italy **Dates:** May 12-18 2026 **Official site:*...

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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://mirror.codeforces.com/blog/entry/66909?#comment-510127) and [this comment](https://mirror.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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Mirror of Bubble Cup 14 Finals on Codeforces Hello, Codeforces! [Microsoft Development Center Serbia](https://www.microsoft.com/en-rs/mdcs) is thrilled to announce the finals of the **14th edition of Bubble Cup competition!** Bubble Cup is an international, **ICPC-style team contest** aimed at university and high school students.  Contest will take place on [Saturday, 9th of October at 10AM CEST](https://www.timeanddate.com/worldclock/fixedtime.html?day=9&month=10&year=2021&hour=10&min=0&sec=0&p1=35), in online format. Winners will be announced at the closing ceremony. You can find more info on the [BubbleCup website](https://www.bubblecup.org/). Just like the previous editions, this final will be followed by an online mirror competition on Codeforces. Mirror will take place on the same day about an hour after the start of the finals &mdash; [contest_time:1599]. Contest will last for **4 hours** and **ICPC rules** will be applied. It will be a comp...

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Mirror of Bubble Cup 13 Finals on Codeforces Hello, Codeforces! Hope you're all safe and well. [Microsoft Development Center Serbia](https://www.microsoft.com/sr-latn-rs/mdcs) is thrilled to announce the finals of the **13th edition of Bubble Cup competition**! Bubble Cup is an international, **ACM-style team contest** aimed at university and high school students.  Contest will take place on [Sunday, 4th of October at 11AM CEST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Bubble+Cup+13+Finals&iso=20201004T11&p1=35&ah=3), virtually. Live results will be available on the official Bubble Cup website (results will be frozen during the last 45 minutes of the competition). Winners will be announced at the closing ceremony. You can find more info on the [BubbleCup website](https://www.bubblecup.org/). Just like the previous editions, this final will be followed by an online mirror competition on Codeforces. Mirror will take place on [Mon...

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Info(1) Cup 2019 (In memory of Mihai Patrascu) Hi! 3rd edition of Info(1) Cup will take place this weekend. More information on the [site](http://info1cup.com/). I'll make this post shorter than usual, if you want extra details, you can just check one of the posts from last years ([here](https://mirror.codeforces.com/blog/entry/58101) or [here](https://mirror.codeforces.com/blog/entry/51171)). This year, we'll have official teams from 27 countries taking part to make this contest memorable. We dedicate this edition in the honor of Mihai Patrascu, one of the greatest Romanian Computer Scientists. We hope that this edition will be even more fun and challenging than the previous ones. You can practice on past problems on [oj.uz](https://oj.uz/problems/source/319). This should give a good idea of the kind of level you could expect from the contest although we try harder and harder to make up more interesting and challenging tasks. We invite you all to join the online mirror of either of the rounds (the national round, approximately div2 ...

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Invitation to 4th Turing Cup Hey everyone, Here's an invitation for all programming lovers to participate in the 4th Turing Cup competition! The Turing Cup is an invitational competition that is organized by one of the most successful informatics competition teams in China, the XinYouDui, and X-Camp. Several top students of XinYouDui: [Chao Li](https://stats.ioinformatics.org/people/2672) (IOI 2012 Gold Medalist)；[Yinzhan Xu](http://stats.ioinformatics.org/people/5059) (IOI 2014 Individual 1st place winner)；[Ce Jin](https://stats.ioinformatics.org/people/5872) (IOI 2016 Individual 1st place winner): Top contestants such as IOI Gold medalists, and other top CPers joined the past contest as well. The 4th Turing Fun cup is open for registration, come and code with us! [Registration link](https://contest.xinyoudui.com/22a) (No Registration Fee) Novice Group: We'd recommend programmers who have completed learning the language and basic algorithms and who are in USACO silver division, are eligible ...

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Meta Hacker Cup Round 1 Meta Hacker Cup Round 1 ======================= Good morning! [Meta Hacker Cup Round 1](https://www.facebook.com/codingcompetitions/hacker-cup/2022/round-1) starts on [Saturday, September 10th](https://www.timeanddate.com/countdown/generic?iso=20220910T10&p0=234&msg=Hacker+Cup+Round+1&font=sanserif) in under 48 hours! You're automatically registered for Round 1 if you solved at least 1 problem in the qualification round. ### Important info: - You'll qualify for Round 2 if you **score at least 15 points** in this round. - You won't know whether your submissions are correct or not until after the contest, so it may be wise to solve more problems than you need in case some of your submissions end up being incorrect. Just like in the qualification round, you'll be given validation data, but there may still be cases not in validation data which could trip you up. - The round will last 24 hours, and you may use as much of that as you would like solving problems. As usual, **you m...

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Meta Hacker Cup Round 2 Meta Hacker Cup Round 2 ======================= Good morning! [Meta Hacker Cup Round 2](https://www.facebook.com/codingcompetitions/hacker-cup/2022/round-2) starts on [Saturday, September 24th](https://www.timeanddate.com/countdown/generic?iso=20220924T10&p0=234&msg=Hacker+Cup+Round+2&font=sanserif) in under 24 hours! You're automatically registered for Round 2 if you scored at least 15 points in Round 1. ### Important info: - You'll qualify for Round 3 if you **place in the top 500** in this round. - If you place in the **top 2000 of this round**, you'll win a limited edition Hacker Cup t-shirt. - If you qualify for Round 3 as well, and you place in the top 200 of round 3, your shirt will have a special "Top 200" badge on it. We put a lot of effort into these problems, so hope you'll find this contest as almost as balanced Codeforces Global Round 5. Good luck, have fun, and we'll see you on the scoreboard! **Update:** [Editorial](https://mirror.codeforces.com/blog/entry/107...

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Meta Hacker Cup 2022 Qualification Round Meta Hacker Cup Qualification Round ================== Good morning! The Meta Hacker Cup Qualification Round starts on [Friday, August 26th](https://www.timeanddate.com/countdown/generic?iso=20220826T10&p0=234&msg=Meta+Hacker+Cup+Qualification+Round&font=sanserif) in under 48 hours! If you haven’t yet, be sure to register on the [Meta Coding Contests](https://www.facebook.com/codingcompetitions/hacker-cup/2022/qualification-round) page. #### Important info: - In order to qualify for Round 1, you’ll need to solve at least one problem in this round. - Once you've registered, you may wish to confirm that the information in your [competition profile](https://www.facebook.com/codingcompetitions/profile) is up to date, including your display handle and which country you’d like to represent. - In Hacker Cup, you run your own submissions on your computer, and upload your source code and the output of your source code to be graded. You’ll have 6 minutes to run your code locally and...

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Meta Hacker Cup Round 3 Meta Hacker Cup Round 3 ================== Good morning! [Meta Hacker Cup Round 3](https://www.facebook.com/codingcompetitions/hacker-cup/2022/round-3) starts on [Saturday, October 8th](https://www.timeanddate.com/countdown/generic?iso=20221008T10&p0=234&msg=Hacker+Cup+Round+3&font=sanserif) in under 48 hours! You're automatically registered for Round 3 if you placed in the top 500 of Round 2. Important info: ------------------ - You'll qualify for the Hacker Cup Finals if you place in the **top 25** in this round. - If you place in the **top 200** of this round, your Hacker Cup shirt will have a badge on the sleeve indicating you did so. - The round will be 3 hours long. Less important advice: ------------------ - Though we attempt to sort the problems in ascending order of difficulty and assign point values appropriately, we particularly encourage reading all the problems in this round. A separate post about t-shirt distribution will be coming in the next few d...

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VNOI Cup 2022 Final round [Mirror invitation] Hello Codeforces! After three elimination round, we are glad to announce the [final round of VNOI Cup](https://oj.vnoi.info/contest/vnoicup22_final_mirror), which which will take place at [2:00 UTC on this Friday, 22th July, ](https://www.timeanddate.com/worldclock/fixedtime.html?msg=%5BMirror%5D%20VNOI%20Cup%202022%20-%20Final&iso=2022-07-22T02:00:00), and it is hosted on our builtin platform — [VNOJ](https://oj.vnoi.info/)! <center> <img src="/predownloaded/d5/f2/d5f2b5827ae8606949ac2cf87b8dd0257af085f1.png" href="VNOI cup 2022 final banner" /> </center> Besides the finalists, this mirror round is open for **everyone**! VNOI Cup is a Competitive Programming competition held by VNOI (Vietnam Olympiads in Informatics community), which is a non-profit organization, by Vietnamese competitive programmers, for Vietnamese competitive programmers. Our aim is to support the growth of competitive programming in Vietnam, and we hope that this competition is one of the things t...

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Info(1) Cup online mirror usaco style Hello everybody! I know that I've updated my first blog regarding Info(1) Cup a lot of times and I might already seem annoying. Well, the fact is that the first blog's main point was registering new countries in the competition and introducing it. This new blog is for those that might not have seen my updates regarding the online mirrors: For about 1 day from now on, you'll be able to take part in any 5-hours frame that you wish in a virtual contest in the exactly same conditions as the official participants had. We find the problems really interesting and we challenge you to solve them all. I'm sure that taking part in this contest should be a positive experience for everyone, so I invite you to participate. The contest is OI like (with partial score based on subtask) and includes an interactive task. You can register and find the link of the contest [here](http://open.info1cup.com/). The [live scoreboard](http://open.info1cup.com:8890/Ranking.html) is on. The live scoreboard ...

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A notorious coincidence (1854E) So one thing led to another and now I'm here to share my results. [Codeforces Round 889 (Div. 1)](https://mirror.codeforces.com/contest/1854) ------------------ As of writting this blog that's the most recent codeforces round and there was some controversy about some problems in it. I'm here to talk about a funny thing that happened involving its div1E. This story starts during the contest. <spoiler summary="You can skip this, it's just me talking about what happened to me before reaching E"> I was taking the contest and thinking about going to sleep after 1 hour without mindsolving anything but A1 but then I ended up solving CBA1. Without being able to notice that my solution to A1 was actually the intended solution to A2 and not having the faith in the gods of AC to just take the minimum of both constructions, I turned into E as I'm notoriously bad at interactive problems. </spoiler> Revisiting E after solving the other problems, I thought "maybe using a bunch of ones and hi...

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VNOI Cup 2022 Round 2 [Mirror invitation] Hello again Codeforces! <!-- Short sentence for invitation --> We are glad to invite you to take part in mirror round of [the second round of VNOI Cup](https://oj.vnoi.info/contest/vnoicup22_r2_mirror), which will take place [at 13:00 UTC, on this Saturday, 25th June](https://www.timeanddate.com/worldclock/fixedtime.html?msg=%5BMirror%5D%20VNOI%20Cup%202022%20-%20Round%202&iso=2022-06-25T13:00:00), and it is hosted on our builtin platform &mdash; [VNOJ](https://oj.vnoi.info/)! <center> <img src="/predownloaded/0c/04/0c04e729c4ba111d2f61cd6aaabd649b844d1887.png" alt="round2-poster" /> </center> <!-- Ask qualified participants to take part in the official round --> **If you are Vietnamese and _qualified_ according to these rules mentioned on [this post](https://cup.vnoi.info/rule/)**, please consider taking part in [the official round](https://oj.vnoi.info/contest/vnoicup22_r2)! <!-- Introduce VNOI --> VNOI Cup is a Competitive Programming competition held by VNOI (Viet...

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Info(1)Cup 2026 teams Hi Codeforces! As you know, Info(1)Cup is coming soon, and I wanted to share the teams from each country. Good luck to everyone who will be participating! Feel free to share your team as well! | Country | 1 | 2 | 3 | 4 | Avg | |--------|---|---|---|---|-----| | Uzbekistan | [user:khba,2026-01-22] | [user:Isamatdin,2026-01-22] | [user:JahonaliX,2026-01-22] | [user:Aisham,2026-01-22] | 1816.5 | | Kyrgyzstan 1 | [user:feev1x,2026-01-22] | [user:Fateless,2026-01-22] | [user:dog,2026-01-22] | [user:saidpon,2026-01-22] | 1775.25 | | Azerbaijan 1 | [user:AzeTurk810,2026-01-22] | [user:Ekber_Ekber,2026-01-22] | [user:Ulvi,2026-01-22] | [user:cMerd,2026-01-22] | 1597.75 | | Egypt | [user:Baraa-Ahmed,2026-01-22] | [user:darkahmed,2026-01-22] | [user:Megalosaurus.,2026-01-22] | [user:nasser_10,2026-01-22] | 1525.5 | | Kyrgyzstan 2 | [user:aktan4ik,2026-01-22] | [user:emirhanbanan,2026-01-22] | [user:Zatic,2026-01-22] | [user:PokemonMaster,2026-01-22] | 1512.25 | | Azerbaijan 2 | [u...

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Meta Hacker Cup 2023 Round 2 Meta Hacker Cup Round 2 ======================= Good morning! [Meta Hacker Cup Round 2](https://www.facebook.com/codingcompetitions/hacker-cup/2023/round-2) starts on [Saturday, October 21st, 10 AM Pacific](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Hacker+Cup+2023+Round+2&iso=20231021T10&p1=234&ah=3) in under 26 hours! You're automatically registered for Round 2 if you scored at least 4 points in Round 1. ### Important info: - You'll qualify for Round 3 if you **place in the top 500** in this round. - If you place in the **top 2000 of this round**, you'll win a limited edition Hacker Cup t-shirt. - If you qualify for Round 3, and you place in the top 200 of Round 3, your shirt will have a special "Top 200" badge on it. You can find more info about T-Shirt details [on this post](https://mirror.codeforces.com/blog/entry/121572). Good luck, have fun, and we'll see you on the scoreboard!

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VNOI Cup 2022 Round 3 [Mirror invitation] Yet again, hello Codeforces! <!-- Short sentence for invitation --> We are glad to invite you to take part in mirror round of [the third and the last elimination round of VNOI Cup](https://oj.vnoi.info/contest/vnoicup22_r3_mirror), which will take place [at 13:00 UTC, on this Saturday, 2nd July](https://www.timeanddate.com/worldclock/fixedtime.html?msg=%5BMirror%5D%20VNOI%20Cup%202022%20-%20Round%203&iso=2022-07-02T13:00:00), and it is hosted on our builtin platform &mdash; [VNOJ](https://oj.vnoi.info/)! <center> <img src="/predownloaded/6d/c7/6dc7ed7087ddae4c89d045b3217e37ade2f8445f.png" alt="round3-poster" /> </center> <!-- Ask qualified participants to take part in the official round --> **If you are Vietnamese and _qualified_ according to these rules mentioned on [this post](https://cup.vnoi.info/rule/)**, please consider taking part in [the official round](https://oj.vnoi.info/contest/vnoicup22_r3)! <!-- Introduce VNOI --> VNOI Cup is a Competitive Programming ...

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Meta Hacker Cup Round 3 Meta Hacker Cup Round 3 ======================= Good morning! [Meta Hacker Cup Round 3](https://www.facebook.com/codingcompetitions/hacker-cup/2023/round-3) starts on [Saturday, November 4th, 10 AM Pacific](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Hacker+Cup+2023+Round+3&iso=20231104T10&p1=234&ah=3) in under 14 hours! You're automatically registered for Round 3 if you placed in the top 500 of Round 2, or had a qualified bye from Round 1. ### Important info: - You'll qualify for the finals if you **place in the top 25** in this round. - If you place in the **top 200 of this round**, your T-shirt prize will have a Top-200 badge on the sleeve, unlike those who earned a shirt but were not in the top 200 in this round. - The round will be 3 hours long. You can find more info about T-Shirt details [on this post](https://mirror.codeforces.com/blog/entry/121572). Good luck, have fun, and try not to get spooked by the problems!

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Order Capital Round 1 (Codeforces Round 1038, Div. 1 + Div. 2) Hello, Codeforces! I am proud to invite you to [contest:2122], which will be held on [contest_time:2122]. The round will be **rated for everyone**. You will be given **7 problems** and **2 hours and 15 minutes** to solve them. All problems were authored by me. I would like to thank: - [user:ntherner,2025-07-07] and [user:TheScrasse,2025-07-07] for coordinating the round, - [user:Radewoosh,2025-07-07], [user:arvindf232,2025-07-07], [user:errorgorn,2025-07-07], [user:Adam_GS,2025-07-07], [user:Errichto,2025-07-07], [user:-XraY-,2025-07-07], [user:Marcin_smu,2025-07-07], [user:Rafi22,2025-07-07], [user:SergeiFedorov,2025-07-07], [user:Markadiusz,2025-07-07], [user:Dragos,2025-07-07], [user:VadymKa,2025-07-07], [user:freak93,2025-07-07], [user:Andrei_ierdnA,2025-07-07], [user:NemanjaSo2005,2025-07-07], [user:fwitt,2025-07-07], [user:ToxicPie9,2025-07-07], [user:madlogic,2025-07-07], [user:Porumb,2025-07-07], [user:ivgechu,2025-07-07], [user:stefdasca,2025-07-07], [user...

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Run-twice (aka communication) problems with Polygon and testlib.h ### Introduction _Run-twice_ problems (also called _multipass_ or _communication_ problems) are problems in which your program is executed twice. Here are some examples: - [problem:2054A] from the TON marathon. - Problems D, G and K from [Universal Cup Season 2 Stage 5](https://assets.ucup.ac/statements/statements-2-5.pdf). - All problems from [Universal Cup Season 2 Stage 16](https://assets.ucup.ac/statements/statements-2-16.pdf). - [Flash](https://boi2019.eio.ee/wp-content/uploads/2019/04/flash.en_.pdf) from BOI 2019 (this one is actually more complicated, but the premise is the same &mdash; there are multiple instances of your program which cannot share data except through the interactor. As you can see, there are many ways this format can be used, but the common themes are encoding/decoding, compression/decompression, constructing a bijection and similar ideas. The general principle is that you have to implement two functions and the second function has to somehow use t...

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Турнир по программированию среди студентов Codemasters Code Cup 2023 Привет, Codeforces! Приглашаем принять участие в [Codemasters Code Cup 2023](https://www.codecup.online/) &mdash; Турнире по программированию среди студентов. Соревнования включают в себя отборочный раунд, который будет проходить онлайн, а также финал и награждение, которые состоятся в Туле.  [Codemasters Code Cup](https://www.codecup.online/) &mdash; турнир, который проводит компания Codemasters International уже четвертый год подряд. Первые три соревнования проводились исключительно в Саранске и Туле, в этом году мы приглашаем к участию студентов со всей России. Соревнование будет организовано в партнерстве с Тульским государственным университетом и Центром олимпиадной подготовки по программированию МГУ им. Н.П. Огарёва. В турнире Сodemasters Code Cup могут принять [участие](https://www.codecup.online/#registration) **студенты и аспиранты очной формы обучения российских учебных заведений в возрасте от 17...

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Codeforces 5 years: Great news! Hello Codeforces! I am happy to announce that the indicated $10000 support fund was raised in a little more than three days! Thanks you very much friends! Now it became possible to pay the writers equivalent funds even they are in rubles. It was impossible because of great increase of the dollar exchange rate. |Round type|USD|Rubles| |-----------|--|---| |Div 1 + Div 2| $250+*$50 | 18000 rub | | Div 2 | $100+*$50 | 9000 rub | <small>We tie the money paid in rubles to the Central Bank of Russia exchange rate, rounded to the closest sum in rubles divisible by 5 (according to the rules of mathematical rounding). The table shows the values that were up-to-date when this post was published. An asterisk marks the bonus that is given if the round is prepared perfectly. </small> And that is not all! As I said before, we now have the opportunity to adequately support the coordinator of the Codeforces problems Max [user:Zlobober,2015-02-27] Akhmdov. He started working on his ...

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Codemasters Code Cup 2024: фокус на искусственный интеллект и бизнес-приложения Началась регистрация на пятый юбилейный турнир [Codemasters Code Cup 2024](https://codecup.online/) &mdash; всероссийское соревнование по программированию среди студентов. Отборочный раунд пройдет онлайн, а финал и церемония награждения состоятся в Туле. Codemasters Code Cup, который проводят компании Кодмастерс Мордовия и Кодмастерс Тула совместно с Тульским государственным университетом, с прошлого года стал Всероссийским событием. В 2023 году в турнире приняли участие около 370 студентов из 63 городов России &mdash; от Санкт-Петербурга до Владивостока. В 2024 году впервые в рамках турнира будет представлен трек «Разработка бизнес-приложений с использованием искусственного интеллекта». Второй традиционный трек &mdash; «Разработка бизнес-приложений». Участники могут принять участие в обоих треках на отборочном этапе, но в финале им придется выбрать один. Все задания рассчитаны на индивидуальное выполнение и разработаны специалистами-практиками компаний Кодмастерс Тула и Кодмастерс...

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Please improve QoL for blogs I'm pretty sure I've spent more time writing blogs than contests on Codeforces. Over time, I've found plenty of rough edges. So this is a plea to the Codeforces team to fix them. I'm effectively going to say "please redo everything" over dozens of paragraphs, but I'll hopefully make the steps to the solution tangible and clear. If this is deemed way too ambitious, few improvements are better than none. [cut] <!-- --> ## Publication time So I write a post in the Codeforces UI, save a draft, update it a few times, think it's ready, and publish it. I open my brand new post and see: > ### Totally not a useless post > By [user:purplesyringa,2024-09-24], history, 3 days ago, In English Okay, wait, "3 days ago"? Oh, right, that's when I saved the first draft. Now people open the post, see "3 days ago", see 0 upvotes, and what do they think? That's right, they think it's garbage because no one's voted positive, so they skip the article. Maybe not everyone's like tha...

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CP mentoring for charity Motivation ------------------ Many people in the CP community are truly concerned about the war in Ukraine. Rightly so, it is currently affecting millions. Regardless of how many political discussions are held here, they don't really change that much. Let's try to address genuine human suffering instead. CP mentoring for charity ------------------ I would like to host a couple of 1-hour CP mentoring sessions this Saturday. The prerequisite for attending one is donating at least 20$ to any charity supporting victims of the war. Of course, you are more than welcome to donate more. If you think this is something for you, sign up for one of the six slots via this Doodle link: https://doodle.com/meeting/participate/id/ZdP68j6a The slot **should** disappear after it is chosen by one person. But I have never used Doodle as a booking management system before, so I don't guarantee that everything will work as planned... we'll sort it out :) Please donate only **after** y...

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Info(1) cup 2021 online mirror? Hi codeforces, I found out by chance that the online mirror of Info(1) cup will start [soon](https://www.info1cup.com/#schedule) but there were no blogs nor registration link on their website ,so, Is the registration still open? If yes, how can I register? [user:geniucos,2021-02-14]

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Midnight Code Cup Qualification Is happening on [April 11th at 1 PM UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=11&month=4&year=2026&hour=13&min=00&sec=0) here on Codeforces. The qual lasts 4 hours. [MCC](https://mirror.codeforces.com/blog/entry/151741#comment-1358025) is a new generation programming contest, with a 24 hour onsite final, broad variety of problems (algorithmic challenges, optimization puzzles, plus some weird problems). You can participate in a team of 3 or less, the use of AI is allowed and encouraged. You can still register, but please do it by the end of the day April 10th to get you log in info in time. Register here: https://midnightcodecup.org/ If you already registered ------------------------- You'll get an email from Codeforces with your login information on April 10th. Log in with those credentials and wait for the problem statements to become available at 1PM UTC on Saturday! **Important:** If you registered through CF yesterday &mdash; this was a registrati...

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Дорешивание задач infO(1)Cup Здравствуйте дорогие программисты! Можете подсказать пожайлуста где можно дорешивать задачи infO(1)Cup 2023?

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Завтра заканчивается регистрация на Codemasters Code Cup Завтра, 9 сентября, в 23.59 регистрация на Всероссийский турнир по программированию среди студентов Codemasters Code Cup будет закрыта. Утром 10 сентября начнется отборочный тур. Турнир проводится по двум трекам: Спортивное программирование и Разработка бизнес-приложений. На отборочном этапе можно принять участие в двух треках, в финале нужно будет выбрать только один трек​. Все задания как отборочного раунда, так и финала, рассчитаны на индивидуальное выполнение. Подать заявку на участие в Codemasters Code Cup можно до 23.59 9 сентября на сайте [www.codecup.online](www.codecup.online).  Отборочное соревнование в треке “Спортивное программирование” будет проходить один день 10 сентября с 11:00 &mdash; 16:00 часов по Москве. Результаты будут объявлены 12 сентября. На выполнение задания в треке “Разработка бизнес-приложений” дается 5 дней. За это время участникам нужно будет реализовать приложение с н...

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До окончания регистрации на Codemasters Code Cup осталось 5 дней **10 сентября стартует отборочный онлайн-раунд Всероссийского турнира Codemasters Code Cup. Финал состоится 28-29 сентября 2023 года в Туле.** Турнир проводится по двум трекам: Спортивное программирование и Разработка бизнес-приложений. На отборочном этапе можно [принять участие](https://www.codecup.online/#registration) в двух треках, в финале нужно будет выбрать только один трек​. Все задания как отборочного раунда, так и финала, рассчитаны на индивидуальное выполнение.  Отборочный раунд будет проходить онлайн, поэтому [принять участие](https://www.codecup.online/#registration) в Турнире могут студенты любого российского вуза. Для участия в Codemasters Code Cup уже зарегистрировались учащиеся таких вузов как МГУ им. Ломоносова, ТулГУ, Сколтех, СТАНКИН, МАИ, ЛЭТИ, МИСИС, МФТИ, ИТМО, РТУ МИРЭА, МТУСИ, НИУ ВШЭ, МГУ им. Огарева, МТУСИ, СПбГУ и пр. География турнира &mdash; от Владивостока до Санкт-Петербурга....

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TeamsCode Summer 2024 Contest Editorial The [TeamsCode Summer 2024 Virtual Programming Contest](https://mirror.codeforces.com/blog/entry/131526) was held on Sunday, July 28. The problems were written and prepared by [user:Yam,2024-07-14], [user:hyforces,2024-07-14], [user:oursaco,2024-01-20], [user:willy108,2024-07-14], [user:jay_jayjay,2024-07-14], [user:HaccerKat,2024-07-14], [user:xug,2024-07-14], [user:yash_9a3b,2024-07-14], [user:Red0,2024-07-16], and [user:superhelen,2024-07-16]. The problems (with problem credits) can be found in the [Novice Gym](https://mirror.codeforces.com/gym/105283) and [Advanced Gym](https://mirror.codeforces.com/gym/105284). [user:lunchbox,2024-08-02] solved all the problems during testing and provided valuable feedback. [Novice A /](https://mirror.codeforces.com/gym/105283/problem/A)[ Advanced A: P!=NP](https://mirror.codeforces.com/gym/105284/problem/A) === <spoiler summary = "Hint"> Try simplifying the equations by dividing by $p$, then think about which values of $p$ would produce a valid value of $n$. </spoiler> ...

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Info (1) Cup official Mirror Hi codeforces, does anybody know link to official mirror of Info (1) Cup or has information when will it be posted on official site? Thank you in advance for response.

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Learning Notes on the Hopcroft-Tarjan planarity algorithm (With C++ Implementation) **Section 1. Introduction** I have been struggling for weeks to understand the first linear-time planarity algorithm, the [Hopcroft-Tarjan algorithm (HT)](https://www.cs.princeton.edu/courses/archive/fall05/cos528/handouts/Efficient%20Planarity.pdf). Fortunately, I successfully understood it and implemented it. In fact it is very hard to find a verified HT implementation online. Some code, e.g., [LEDA](https://en.wikipedia.org/wiki/Library_of_Efficient_Data_types_and_Algorithms) is not open source. Other open-source planarity tests, e.g., [networkx (LR planarity)](https://github.com/networkx/networkx/blob/main/networkx/algorithms/planarity.py), [boost (Boyer-Myrvold)](https://www.boost.org/doc/libs/1_53_0/libs/graph/doc/boyer_myrvold.html), [Pigale (LR planarity)](https://pigale.sourceforge.net/), use other algorithms. There is [an implementation by Shawn Anderson](https://github.com/shawnwanderson/Hopcroft-Tarjan-Planarity-Testing), however it is partial. I would like to open a blo...

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InfO(1) Cup 2023 - where to submit? Hey, As the contest had already ended more than a month ago, I've trying to find any OJ where it'd be possible to submit problems from InfO(1) Cup 2023, but I couldn't find any. Is there any online judge where it can be done? Thanks in advance!

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Hello Codefroces, can you help me ? Hello Codeforces, Where can I found archive of Info(1) cup 2018? I will be very grateful, if you give a link.

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info(1)cup 2026 where i can find info(1)cup 2026 tasks?

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