কি অবস্থা ব্রো? আবারও চলে এসেছি! (That's Bengali for "What's up bro? I am back again!")

I am super excited to invite you to participate in CodeTON Round 9 (Div. 1 + Div. 2, Rated, Prizes!) which will be held on Nov/23/2024 17:35 (Moscow time). This round is rated for both divisions.

The contest will feature $$$8$$$ problems, with three of them divided into two subtasks each. You will have $$$3$$$ hours to solve as many as you can. The problems are authored and prepared by me and wuhudsm.

I would like to thank -

• TheScrasse and Kaey for their jaw-dropping (literally) coordination of the round, giving valuable feedback and improving lots of problems.
• wuhudsm for being kind enough to use one of his cool problems in the round.
• Alpha_Q and Raiden for discussing tons of problems with me and improving some problems.
• antontrygubO_o for not participating in the round as he knows some of the problems as my past coordinator.
• dorijanlendvaj, wyrqwq, Thienu, wuhudsm, jdurie, Farhan132, Soumya1, nfssdq, redpanda, LMeyling, upobir, AlephZero01, NemanjaSo2005, Alpha_Q, tb_ro, Kawchar85, waidenf, serotonin, dazlersan1, I_Love_you_Tithi, Random_3652, and Raiden for testing and improving the round.
• redpanda for creating awesome Manim video editorials for some of the problems.
• The great MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• You, for existing and participating in the round. Also, thanks for giving your best and not quitting. You will get what you want prettyyy soon. Just hold right there .

Score distribution: TBA

Wishing you TONs of luck — hope you have a TON of fun cracking the problems!

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 9.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 9 will receive valuable prizes.

The first 255 participants will receive prizes in USDT cryptocurrency in the TON network:

• 1st place: 2,560 USDT
• 2–3 places: 1,280 USDT each
• 4–7 places: 640 USDT each
• 8–15 places: 320 USDT each
• …
• 128–255 places: 20 USDT each

We wish you good luck at CodeTON Round 9 and hope you enjoy the contest!

Hi everyone!

For the Winter 2025 edition of the Osijek Competitive Programming Camp (OCPC), we are working with the National University of Singapore (NUS) to host a mirror of the OCPC in Singapore, during 22-26 Feb 2025. The mirror will consist of 4 training contests, that are a subset of the main 7 contest of the OCPC (scheduled for 15 Feb-23 Feb 2025 in Osijek, Croatia and online, will be officially announced later).

The contest days will be on 22, 23, 25 and 26 Feb, and 24 Feb will be a rest day. The mirror takes place right before ICPC APAC Championship 2025, scheduled for 27 Feb-2 Mar, and is a good training opportunity for its participants. Please note that the mirror is a private initiative of NUS and OCPC, and is not an official part of the ICPC event.

If you want to get a feel of the contests, refer to this comment for past public OCPC contests.

We are still looking for problem-setters for this edition's OCPC. If you are interested in problem-setting, please contact adamant. We are especially interested in problem-setters who can come onsite to give live editorials. Refer to this post for more details.

Registration

The participation fee for the mirror is 50 SGD per person, and it is only possible to participate in person. Please note that it does not include travel, accommodation or meal expenses. If you want to participate, please register here before 10 Feb 2025.

FAQ

Will the contest system be the same as the ICPC APAC Championships?
You will use the same physical set-up, but we will be in a different room in NUS. The online judge used will also very likely be different.

Are teams that are not attending the ICPC APAC Championships allowed to come?
Yes, you are welcome to come.

What is included in the costs?
In addition to the contest system and problems, snacks and a final dinner will be included in the costs. Again, it does not include travel, accommodation or meal expenses.

If you have any other questions, please write them in the comments below!

Note that initially this contest was scheduled on a different day. Due to technical difficulties, we had to postpone the online mirror. We are sorry about that; if you planned to participate, but are no longer able because the contest day has changed, you can use the virtual participation option.

Hello Codeforces!

The Southern and Volga Russian Regional Contest was held in Saratov State University yesterday, on 12th of November. This contest was used to qualify the teams from Southern Russia and Volga region to the Northern Eurasia Finals.

On Nov/18/2024 13:35 (Moscow time), we will conduct the online mirror of this contest. It will last for 5 hours and is best suited for teams of three people, although it is not forbidden to participate in teams of smaller/larger size. The mirror will use ICPC rules, the same as the offline contest.

The contest was prepared by adedalic, awoo, dmitryme, elena, Neon, DmitryKlenov, MikeMirzayanov, Ferume and me. Big thanks to the contest testers: Kuroni, ashmelev, bthero, KIRIJIJI, Kniaz, vladmart, JanPlovLagman, H3nTa1, pshenikita. I would like to express my gratitude to MikeMirzayanov for not only participating in the preparation process himself, but also making Polygon, which made our work much easier.

As the chief judge of the contest, I hope you enjoy the problems!

Of course, the contest will be unrated.

Welcome to Natlan, Codeforces!

Toyac Springs, Natlan

sum, vgoofficial and I are like a dog with two tails to welcome you to participate in Codeforces Round 988 (Div. 3) at Nov/17/2024 17:35 (Moscow time). We have cooked up $$$7$$$ problems to be solved in $$$2$$$ hours and $$$15$$$ minutes.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks. After open hacks all accepted solutions will be rejudged on successful hacks.

Note that the penalty for each wrong submission in this round is 10 minutes. Also, note the rule restricting AI use!!! If you are caught using AI in an unorthodox manner, bad things will happen to you. We will be watching you all...

IMPORTANT!!! There is at least one interactive problem in the problemset. Please familiarize yourself with the guide for interactive problems beforehand.

Remember that only the trusted participants of the third division 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 trusted participant of the third division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them)
• do not have a rating of 1900 or higher at any moment in time.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you (unless you register unrated).

We would like to orz the following individuals for making the contest possible:

• Vladosiya for the pogU coordination.

• Our army of testuwuers: (VIP) Dominater069, amoeba3, LMeyling, awesomeguy856, AlperenT, Error_Yuan, 18o3, Intellegent, efishel, Edeeva, Lilypad, wuhudsm, Vladosiya, Filikec, kevlu8, (VIP) chromate00, Prady, mathtsai, AdityaTakkar, larush, RobinFromTheHood, macaquedev, and dazlersan1.

• MikeMirzayanov for being MikeMirzayanov.

UPD: Editorial!!!

Hello Codeforces!

We (pwned, ACGN, HappyPacMan, maomao90, AverageDiv1Enjoyer, and trunkty) are thrilled to invite you to Codeforces Round 987 (Div. 2) on Nov/15/2024 15:35 (Moscow time) (note the unusual time)! After more than two years of preparation and nearly thirty problems on our shortlist, our contest is finally here for your enjoyment!

In this round, you will help Penchick as he embarks on a world trip through the Philippines, Indonesia, and even through the Australian beaches and attempt six problems in two hours!

The score distribution will be as follows: $$$500-1000-1500-2000-2500-3000$$$.

This round would not be possible without the support of everyone behind this round:

• maomao90 and KAN for their excellent coordination and problem setting,
• pwned, ACGN, AverageDiv1Enjoyer, and trunkty for the creative tasks,
• HappyPacMan for his amazing technical skills in making the problems come to life,
• Alexdat2000 for translating problem statements,
• PiejanVDC, Shrimb, heavylightdecomp, ryuusama, and SlavicG for their unique problem ideas,
• ArvinCiu, Irmuun.Ch, bestial-42-centroids, dbscts, zscoder, NeroZein, and wfe2017 for their advice in creating interesting problems,
• _Body, ljuba, Dominater069, pavement, Rideris, Error_Yuan, NovusStellachan, Dan4Life, lunchbox, DilshodbekX, SHZhang, micho, Muhammad-Saram, culver0412, ErrorAssassin, AlperenT, iLoveIOI, newb_programmer, mwen, Erering, LMeyling, and AkiLotus for testing our round and providing invaluable feedback, and
• You for being an awesome member of the CF community!

Lastly, we thank MikeMirzayanov for creating the incredible Codeforces platform, where many of us have engaged in friendly competition, honed our problem-solving skills, and forged lasting friendships throughout the years!

From our keyboard to yours, we (and Penchick) wish you good luck, positive delta, and an exciting competition experience!

Note: There is at least one interactive problem, so please read the guide for interactive problems if you are unfamiliar with them.

UPD: Editorial has been posted, go check it out!

UPD: Congratulations to the winners!

Div. 1 + Div. 2:

1. tourist, as expected, fully solving all problems in 53 minutes
2. antontrygubO_o, who did so just 2 minutes later
3. noimi
4. A_G
5. Pyqe
6. StarSilk
7. dyppp
8. kotatsugame
9. busamate
10. tarjen

They, along with 8 other contestants, are the only AKers (full-solvers) in the whole contest!

Div. 2 only:

1. LGlcx, who full-solved in 100 minutes!
2. Sky_Maths
3. G2Esports
4. boboquack
5. ac_de_taffy
6. Jack.YT
7. Alex2184
8. MrPizza
9. priyanshu.p
10. CC_cccc

We hope you all enjoyed the round!

Hello Codeforces!

I am glad to invite you to Codeforces Round 986 (Div. 2), which will start on Nov/10/2024 18:35 (Moscow time). Note the slightly unusual start time.

The contest will run for 2 hours and have 6 tasks. The contest will only be rated for those with a rating not higher than 2099, but we welcome higher rated users to participate out of competition.

Holding the contest would have been impossible without:

• flamestorm for insanely excellent coordination, without whom this round would certainly not happen.
• Vince729 and swagchicken for lots of discussions about the problems and proposing other problem ideas :)
• conqueror_of_tourist, BucketPotato, Dominater069, sstrong, triple__a, xiaowuc1, lucasxia01, n0sk1ll, nikilrselvam, thanhchauns2, AkiLotus, bibimoni, CSQ31, mp1309, Non-origination, Qualified, redpanda, dazlersan1, fatant for testing and giving a ton of useful feedback!
• MikeMirzayanov for the wonderful Codeforces and Polygon platforms.

and of course a special thank you to all of you for participating!

Score Distribution: $$$500-1000-1500-1750-2000-2500$$$.'

UPD: The Editorial is now published.

UPD2: Congratulations to the winners!

Div 1:

1. jiangly
2. A_G
3. BurnedChicken
4. MAKMED1337
5. maspy

Div 2:

1. SUPERLWR-beta
2. mychecksdead
3. sweet_dream
4. contee
5. Sunflower233

First solves:

• A: podyapolskiy.yaroslav in 00:01:14
• B: potato167 in 00:07:38
• C: thembululquaUwU in 00:09:18
• D: jiangly in 00:17:37
• E: golions in 00:17:54
• F: MAKMED1337 in 00:10:29

Hello, Codeforces!

We (KDOI Team) are glad to invite you to take part in Refact.ai Match 1 (Codeforces Round 985), which is the 8th CP contest held by us! You can view the previous rounds by us here.

• Number of problems: $$$9$$$ ($$$0$$$ interactive);
• Start time: Nov/09/2024 17:35 (Moscow time);
• Contest duration: $$$180$$$ minutes;
• Score distribution: $$$750-1250-1750-2250-2500-3000-3500-5000-5500$$$.

The problems were authored and prepared by Error_Yuan, wyrqwq, Otomachi_Una and me sszcdjr.

A few words from our sponsor:

We’re Refact.ai, an open-source AI Coding Assistant, and on November 9th, we’ll be hosting our first round on Codeforces! Winners will receive valuable prizes, and all participants will have a chance to get some exclusive merch from us.

Refact.ai is pushing AI beyond simple code completion. Soon, we’ll launch the Autonomous AI Agent—a developer’s buddy that handles real engineering tasks end-to-end, from planning and coding to testing and deployment. You can read more about us in this announcement.

If you're excited about AI in software development and want to build the future instead of focusing on the trivial, join Refact.ai, founded by a former OpenAI researcher. We’re looking for talented Researchers and Backend developers to join our team.

Prizes:

• 1st place: 500 USDT
• 2nd place: 300 USDT
• 3rd place: 200 USDT
• 4-5th place: 100 USDT
• Top 50 participants will get T-Shirts
• Additionally, 50 random participants from the top 51-500 will receive a T-shirt

Good luck in the contest!

On the right, badges of the authors. From top to bottom, left to right are Error_Yuan, Otomachi_Una, sszcdjr and wyrqwq respectively.

We would like to thank:

• Vladithur for his wonderful coordination.
• Again, Vladithur for the Russian translation.
• programpiggy for providing a few unused problems.
• gyh20, dXqwq, Sugar_fan, 275307894a, Kubic, PEIMUDA, A_zjzj, LMydd0225, abc864197532, N_z__, rui_er, ProjectCF, chenyifanlx, MatrixGroup, wsc2008qwq, EasonLiang, cayaxi09, Hanghang007, SpadeA261, IwannaEATaCUTEcaca-qwq, OctoberEstuary, MrPython, acwing_gza, chromate00, mathtsai, Codula, tibinyte for testing and giving useful feedbacks.
• You, for participating and getting positive delta.
• Last but not least, MikeMirzayanov for great Polygon and Codeforces platforms.

Good Luck & Have Fun!

UPD1. The Editorial was published.

UPD2. Congratulations to the winners!

1. Benq
2. jiangly
3. hos.lyric
4. Radewoosh
5. arvindf232
6. Nachia
7. ksun48
8. Szoboszlai10
9. Endagorion
10. _Serge_

Hello Codeforces!

Hello Codeforces! As we wrap up another exciting round of our Kotlin Heroes series, it’s time to celebrate the champions who navigated the challenges like pros. With high stakes and impressive typing speeds, we witnessed incredible talent. Join us as we highlight the winners!

The top three contestants:

1. arvindf232
2. tourist
3. Golovanov399

A Kotlin Heroes T-shirt and exclusive Kotlin stickers will be presented to:

These participants also won branded T-shirts:

We will contact the winners soon to coordinate the delivery of their prizes!

It's great to see new people learning Kotlin and performing brilliantly in the competition. Challenges from all eleven previous rounds are available for practice here: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, Episode 8, Episode 9, Episode 10 and Episode 11.

For those who would like to get to know Kotlin better, take a look at Basic Kotlin (solve Koans), Kotlin Playground, this competitive programming tutorial, and these videos on competitive programming in Kotlin.

We wish you luck and hope you enjoy Kotlin!

Hello, Codeforces.

We're Refact.ai, an open-source AI Coding Assistant, and on November 9th, we'll be hosting our first round on Codeforces! It will be a combined Div.1+Div.2 round. Welcome!

The winners will receive valuable prizes, and all participants will have a chance to get some exclusive merch from us.

Refact.ai is pushing AI beyond simple code completion. Soon, we'll launch the Autonomous AI Agent—a developer's buddy that handles real engineering tasks end-to-end, from planning and coding to testing and deployment.

If you're excited about AI in software development and want to build the future instead of focusing on the trivial, join Refact.ai, founded by a former OpenAI researcher. We're looking for talented Researchers and Backend developers to join our team.

We already have competitive programmers on board, such as humbertoyusta and Rox. As humbertoyusta puts it, "Working at Refact.ai feels like being part of a team that's constantly pushing the boundaries of what's possible." If that sounds like your kind of environment, fill out this form for full-time positions (remote or in Barcelona).

If you're not open to new job opportunities but want to delegate tedious tasks and climb the leaderboard faster, explore: Refact.ai — an Open-source AI Coding Assistant that helps you create more while coding less.

Refact.ai already empowers you to code smarter. How?

• Built around your codebase, it provides accurate auto-completions powered by best-on-market Retrieval-Augmented Generation (RAG).
• Integrated in the IDE chat is already aware of your codebase and answers your questions right within your editor. (Compare it with Copilot and see the real power:)
• Detects and fixes bugs, writes unit tests, explains complex code, and much more!

Assign tasks in natural language, select from models like GPT-4o, GPT-4 Turbo, Claude 3.5 Sonnet, or Grow-Llama-3.1, and Refact.ai will generate the code for you.

• Get 3 months of the Pro Plan for free: Refact.ai has a special gift for the Codeforces community. Just use the promo code CODEFORCES to redeem it.

• Join the Discord community: Collaborate with like-minded developers and discuss the latest news and research.

• Contribute to Refact.ai: As an open-source project, Refact.ai welcomes your contributions—join us in building the future of programming together!

We hope you enjoy the problems and have a great time participating in the round!

Привет, Codeforces!

Хотим пригласить вас поучаствовать в Codeforces Round 984 (Div. 3), который состоится в 02.11.2024 17:35 (Московское время). Вам будет предложено 7 задач и 2 часа 15 минут для их решения. Штраф за неверную попытку будет равняться 10 минутам. В раунде могут быть интерактивные задачи.

Раунд пройдет по правилам образовательных раундов. Таким образом, во время раунда задачи будут тестироваться на предварительных тестах, а после раунда будет 12-ти часовая фаза открытых взломов, после её завершения все успешные попытки будут перетестированы на успешных взломах. Мы постарались сделать приличные тесты — так же как и вы, мы будем расстроены, если у вас будут падать решения после окончания контеста.

Напоминаем, что в таблицу официальных результатов попадут только достоверные участники третьего дивизиона. Это вынужденная мера для борьбы с неспортивным поведением. Для квалификации в качестве достоверного участника третьего дивизиона надо:

• принять участие не менее чем в пяти рейтинговых раундах (и решить в каждом из них хотя бы одну задачу)
• не иметь в рейтинге точку 1900 или выше.

Независимо от того являетесь вы достоверными участниками третьего дивизиона или нет, если ваш рейтинг менее 1600, то раунд для вас будет рейтинговым.

Задачи были составлены и подготовлены командой, состоящей из Seny, eugenechka.boyko.2_0-0 и меня.

Раунд основан на прошедшей недавно Липецкой командной олимпиаде школьников по программированию. Обратите внимание, что если вы являетесь участником олимпиады, вам не разрешается участвовать в этом раунде. Спасибо координатору этой олимпиады myav и составителю Small_machine, задачи которого не вошли в этот раунд из-за высокой сложности.

Мы очень благодарим:

• Vladosiya за прекрасную координацию
• 74TrAkToR, Sokol080808, FBI, ssor96, itz_pabloo, IceHydra, justlm, SashaT9, nirjoy_139, lorenzotinfena за тестирование раунда
• MikeMirzayanov за создание замечательных платформ Codeforces и Polygon
• Вас за участие!

Мы надеемся, что задачи покажутся вам интересными. Удачи!

UPD.: Разбор