Ready to Duel?

If yes, FetFot, Intellegent, and I are glad to invite you to Codeforces Round 1025 (Div. 2), which will be held on 17.05.2025 17:35 (Московское время).

This round will be rated for participants with rating lower than 2100. We will also be glad to see the participants with a higher rating to participate in our round unofficially!

You will be given 6 problems (with at least one interactive problem and one problem that has 3 versions) and 2 hours and 15 minutes to solve them. Also you can read about interactive problems here.

Please take a look at the score distribution; it may help you during the contest. Additionally, make sure to read all the problems.

We would like to thank:

• satyam343, our great beloved coordinator.

• Kaitokid, rui_er, TripleM5da, N_z__, _istil and Dominater069 for red testing.

• ApraCadabra, The_Hallak, Vectors_Master, Mohanad_Nahhal, Wael_Zaiback, TyroWhizz, amoeba4, kingmessi, JagguBandar, Proof_by_QED, limbo16, 18o3 and myst-6 for yellow testing.

• ALAov, Friedrich and THE_THUNDERSTORM_BEGINS for purple testing.

• ZaiBug, larush, MaherSefo, jampm, Non-origination, ALnQ417, chromate00 and SpyrosAliv for blue testing.

• The_Weighted_MST, Nahhas, lucaski2, theweakestsilver and segtreebeats for cyan testing.

• Alexdat2000 for the Russian translation.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

• You

  for participating in this round and gaining positive delta!

The score distribution will be as follows:

To make this blog special, I'd love to share a picture of one of my favorite Yu-Gi-Oh! cards. It would be exciting if you could do the same and share your favorite card in the comments! Together, we can create a nice deck to play with.

UPD 1: Editorial has been posted. Check it out!

UPD 2: Congratulations to the top duelists!

All participants:

1. maspy
2. kotatsugame
3. arvindf232
4. antontrygubO_o
5. StarSilk

Rated only:

1. lunyi
2. jiazhichen844
3. _WD_
4. Zeyush
5. SudoXue

First duelist to beat challenge:

• A: A_G at 00:01.

• B: AndrewNguyen at 00:02.

• C1: Narziss at 00:08.

• C2: BurnedChicken at 00:10.

• C3: golomb at 00:20.

• D: sammyuri at 00:10.

• E: hyman00 at 00:26.

• F: dXqwq at 00:44.

Hello, Codeforces!

eren__, sweetweasel, and I are glad to invite you to Codeforces Round 1024 (Div. 1) and Codeforces Round 1024 (Div. 2). Both rounds take place at 11.05.2025 17:35 (Московское время), and have a duration of 2 hours and 30 minutes.

The Division 1 contest is made up of $$$6$$$ problems, and the Division 2 contest is also made up of $$$6$$$!

We would like to thank:

• maomao90 for his wonderful coordination and huge help in preparing the round.
• Alexdat2000 for the Russian translations.
• Our testers: mmdrzada, N_z__, Hamed_Ghaffari, Shahrad_Mirzaei, RSAMSD, -this-is-obd-, AmShZ, AlefHeKaaf, beny_kh, Nariman_MT, sohsoh, Shayan86, Nimazare, Amoo_Safar, _R00T, Um_nik, AriaH, KiaRash24, AmirAli-Asgari, RadRah, NK_, FrontMan., Ali_BBN, AustinJiang, dshfjka, aram.hosna, arvindf232, larush for testing the round and providing valuable feedback.
• MikeMirzayanov, KAN for the amazing Polygon and Codeforces platforms.
• You, for participating in the round and gaining a positive delta!

This is our first (and hopefully not the last) contest on Codeforces, so we really hope you will like the problems. Don't forget to have fun!

The score distribution of the rounds is as follow:

Division 1:

Division 2:

In the end, here’s a behind-the-scenes photo of the authors putting in the effort to bring you a fun round!

UPD1: The contest is now over. Congratulations to the winners!

Div. 1:

1. Radewoosh

2. tourist

3. maspy

4. Ormlis

5. rainboy

Div. 2:

1. 2ky

2. LuOH3_

3. Untitled_unrevised

4. toku4388

5. Horrible120

UPD2: The Editorial is now out.

Hello, Codeforces!

auiunu, NahC0el and me are glad to invite you to the last round with 10 binary bits — Codeforces Round 1023 (Div. 2), which will start on May/05/2025 17:35 (Moscow time). You will be given 6 problems and 1 subtask with 2 hours 15 minutes to solve them.

The round will be rated for participants of Division 2 with a rating lower than 2100. Division 1 participants can participate unofficially.

All problems are authored by auiunu, NahC0el and me.

We would like to thank:

• Dominater069 and TheScrasse for their wonderful coordination and huge help in preparing the round.
• Alexdat2000 for the Russian translations.
• hyman00, le0n, Flamire, jeroenodb for LGM testing.
• Sana, N_z__, Wuyanru, Little_Bunny, platter, yeminghan, MridulAhi, xuyifei1, Error_Yuan, nifeshe, wfb, _istil for red testing.
• Intellegent, Proof_by_QED, TyroWhizz, Coffee_zzz, yoru_sacri, Edeeva, Caylex, satyam343, luuia for yellow testing.
• rewhile,unforgettablepl, Friedrich for purple testing.
• SpyrosAliv, beaten_by_ai, yashbihany, oviyan_gandhi, hyhcnzjsx, starrykiller, mathtsai, macaquedev, AG-88301, avighnakc, SkyWave2022, chromate00 for blue testing.
• STAR_light_ for black testing.
• MikeMirzayanov for the great Codeforces and Polygon platforms.
• You for participating.

The score distribution is $$$250-750-1500-2000-2750-(2250-2500)$$$.

We hope you will enjoy and have fun in the contest. Good luck!

UPD: Congratulations to the winners and first solves!

Div. 1+2:

1. peti1234
2. maspy
3. Mangooste
4. Sugar_fan
5. risujiroh

Div. 2:

1. _VanGogh_
2. rainboy
3. If_I_lose_it_all
4. typeshit
5. IHaveNoMouth_IMustScream

First solves:

• Problem A: Hamed_Ghaffari at 00:01.
• Problem B: arvindf232 at 00:03.
• Problem C: arvindf232 at 00:08.
• Problem D: Wansur at 00:22.
• Problem E: SSerxhs at 00:29.
• Problem F1: peti1234 at 00:14.
• Problem F2: conqueror_of_tourist at 00:33.

UPD2: Editorial is out!

Hi everyone!

Supported by

... And a happy May day!

We are very happy to announce that OCPC (formerly, the Osijek Competitive Programming Camp) is back this Summer, on June 21-29, 2025! While the dates are pretty tight, they appear to be the ones that are most suitable (among all the summer internships, exams, other coding events, etc) for the majority of people who filled the dates questionnaire.

This time, the camp is hosted by the Faculty of Mathematics and Computer Science of the University of Bucharest in Bucharest, Romania and is brought to you by the organizing team of adamant, -is-this-fft- and livlivi.

The camp is inspired by various competitive programming camps that we attended during our active years in ICPC, and is aimed to help college students prepare for ICPC regional contests and finals. The camp will consist of 7 ICPC-style contests and 2 days off.

Mirror camps

Before going into further details, we would also like to announce that we expect the following mirror sites this Summer:

• India: OCPC with the collaboration of GoForGold and ICPC India will have an onsite mirror for top teams from India, so if you are one of the world finalist or got top rank in this year Asia West Finals and have chances left for world finals then you can join Indian mirror which will be scheduled during the second half of July.

• Indonesia: We will also organize a mirror site on the premises of the Bina Nusantara University (BINUS) in Jakarta for people based in the APAC region. This mirror is planned to be held in the late August, shortly before ICPC World Finals.

The mirror sites use the same consest sets, but typically have a different organizing team (for example, this winter, a mirror in Singapore, APAC was organized by errorgorn). As the mirror sites will happen after the European (and online) camp edition, they will be properly announced later on. Mirror sites are primarily intended for onsite participation, so if you are geographically located in the corresponding region (or are willing to go there for the camp), we encourage you to wait for the corresponding announcement.

If you want to participate remotely or in Europe, please register for the Bucharest edition of the camp (the one announced here).

Details

The participation fee for both online and onsite participants is 201€ per team.

Similar to previous camp editions, the fee does not include regular meals, travel or accommodation.

We support and empathize with those affected by the ongoing war in Ukraine, therefore we offer a free participation for affected individuals and teams affiliated with Ukrainian institutions.

The expected starting time for the contests is 10am CEST. For remote participants, it is still a preferred starting time, but we will make accommodations for virtual participation at a later time, when necessary.

Most of our contests are originally developed for the camp. A small number of contests may be based on previous contests that have not been released to the general public. If you have seen some problems of a contest before, you can't participate on that day. We will privately contact participants who might be affected.

After the camp, we will have a silence period during which camp materials will not be released to the public. We ask participants not to discuss the problems in public unless they obtained an explicit permission from contest authors.

If you would like to get a feel of the contests, you can find links to some of the previously published camp contests here.

If you have any questions about the camp, please feel free to send us an email, or join our Discord server!

Participants

If you are interested in participating, please fill the form here.

We ask you to register before June 14 if you want to participate remotely and before June 7 if you want to participate in Bucharest. If you require a visa, please register as soon as possible, as it might take a few weeks to receive (depending on your location).

Also, if your university or organization has a lively ICPC community that may be interested in attending the camp, and you have some contacts of people in charge (e.g. coaches) we would highly appreciate if you could share some details in a direct message to me. Thanks!

Problemsetters

We'd like to thank and praise the authors of the contests in the camp:

• conqueror_of_tourist — ICPC 2022 world finalist and NAC 2025 winner.
• Pyqe — IOI gold medalist, author of IOI 2024 Nile and Tree.
• Kinon — IMO bronze, silver, and gold medalist.
• jtnydv25 — Problemsetter for OCPC 2023 Fall.
• p-square — IOI and IMO Bronze medalist, 3 times IMO Gold medalist.
• sidhant — IOI Bronze medalist.
• blue — 2 times IOI Silver medalist.
• LuCpp, dranjohn, imirdy — ICPC finalists 2024 and 2025, NWERC 2024 Winners.
• AmirrzwM — ICPC World Finalist (2024, 2025), author of Codeforces and Rayan Rounds, and INOI (Iranian National Olympiad in Informatics) Silver Medalist.
• MohammadParsaElahimanesh — Author of Codeforces and Rayan Rounds, INOI Silver Medalist, and top problem solver on Quera.
• DeadlyCritic — Author of contests on Codeforces and INOI Silver Medalist.
• chromate00 — Coauthor of OCPC Potluck Contest 2, enjoyer of multiple rare techniques.

... And others! You can find more details about contest rules and technical setup on the website.

Special thanks

Finally, we say special thanks to

• our sponsors, who make the camp possible;
• ICPC foundation for their help and support;
• Codeforces for support and guidance;
• eolymp for providing an online judge for the contests;
• Faculty of Mathematics and Computer Science of the University of Bucharest for hosting the camp;
• School of Applied Mathematics and Computer Science of the University of Osijek for the invaluable help and providing a physical location for the camp in the previous editions of the camp.

こんにちは, Codeforces!

Since our first round, we've learned a lot, and now we're excited to invite you to participate in Codeforces Round 1022 (Div. 2), which will be held at May/01/2025 17:35 (Moscow time). The round will feature 6 OR 7 full Leetcode implementation problems, where OR means the bitwise "we don't know" operation, and you'll have 2 hours to solve them. Some of the problems might be interactive — you can read more about interactive problems here.

The round will be rated for all participants with a rating below 2100, but everyone is welcome to participate out of competition as well.

All problems were authored and prepared by m3tr0, suprend, and me.

We would like to express our huge thanks to Akulyat for the fantastic coordination of the round and playing $$$\text{Tower Defense}$$$, as well as to all our testers:

• A_G for red-black-tree style testing.
• NemanjaSo2005, sammyuri, and N_z__ for bloody testing.
• Proof_by_QED, mwen, and KiKoS for sparagmos testing.
• xelsink1 and Hausdorf for gangway testing.
• ko0g, larush, and Ratery for heavenly testing.
• ne_justlm, Plotva, and Sobaka_ulybaka for testing the color of the flying stone.
• chepvl for testing the color of the spanning tree.

And, of course, huge thanks to MikeMirzayanov for the すばらしい Codeforces and Polygon platforms, and You for participating!

UPD1: Score distribution: $$$500-1250-1500-2250-2750-3250$$$

UPD2: Congratulations to all the fighters of trees and towers! The final mousing:

All participants:

1. peti1234
2. BurnedChicken
3. potato167
4. propane
5. jiangly

Moused only:

1. 2018LZY
2. ft2007
3. pzjQWQ
4. cooluo
5. under1oop

UPD3: Editorial is here!

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos.

On Apr/28/2025 17:35 (Moscow time) Educational Codeforces Round 178 (Rated for Div. 2) will start.

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 adedalic Dalabaev, Mikhail awoo Piklyaev, Maksim Neon Mescheryakov, Alex fcspartakm Frolov and me. We would like to express our gratitude to Alexey ashmelev Shmelev for testing the problems and providing us with lots of useful feedback. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

The round is partially based on the Saratov Multi-University Olympiad and the Nizhny Novgorod Regional Collegiate Olympiad, so if you participated in any of these two competitions, please skip the round.

Our friends at Neapolis University Pafos also have a message for you:

Admission to the Computer Science and Artificial Intelligence Bachelor’s program at Neapolis University Pafos is ongoing!

The JetBrains Foundation is offering 20 fully funded scholarships for talented first-year students.

Each scholarship covers the entire duration of the program, including tuition, accommodation, medical insurance, visa fees, and €300 per month for personal expenses.

Good news! If you missed the first round, there’s still time to apply for the second round! Submit your documents, pass the entrance test and interview, and receive a full scholarship.

• Application deadline – June 12, 2025
• Entrance test – June 15, 2025 (this is the last entrance test for 2025!)

Additionally, there are 2 fully funded scholarships available for students wishing to transfer into the second year of the program (for those already studying Computer Science).

If you have any questions, feel free to ask in the Telegram chat or email us at [email protected] !

upd: Unrated registration is possible now. Sorry for the inconvenience.

upd2: The editorial can be accessed here.

Hello everyone!

We at TON Studio are proud to present the Tact Smart Battle 1, a week-long smart contract coding competition powered by the Tact language. This challenge is designed to push your problem-solving skills to the limit as you tackle real-world blockchain development tasks on The Open Network (TON). With a $20,000 prize pool and unique opportunities for recognition, we invite you to join this exciting event.

About the Challenge

Participants will solve five progressively complex tasks focused on building efficient voting systems. Each task is crafted to test different aspects of smart contract development:

1. Simple Voting: — basic voting system.
2. Serial Voting: — multiple proposals via a master contract.
3. Scalable Voting: — support up to 4 billion voters.
4. Voting with Refunds: — refunds to voters.
5. Gas-Managed Voting: — fully optimized contracts.

Prizes

• The $20,000 prize pool (in Toncoin) will be shared by the top 128 participants based on contest rankings.
• All participants who submit valid solutions will receive a Soulbound Token (SBT), a non-transferrable token that highlights your contribution on-chain.
• Top performers will earn exclusive SBTs to showcase their achievements.

Outstanding contestants may also receive interview invitations from TON Studio for career opportunities in blockchain development.

Contest Timeline

Start: April 21, 12:00 UTC+3
End: April 28, 12:00 UTC+3

Why Compete?

This event is more than a contest — it’s a chance to hone your skills in cutting-edge blockchain development, earn tangible rewards, and build your reputation within the TON ecosystem. Whether you’re a seasoned coder or exploring smart contracts for the first time, the Tact Smart Battle offers a platform to learn, innovate, and prove your expertise.

For questions or technical assistance, visit the official Telegram chat.

We look forward to seeing your creativity, efficiency, and problem-solving prowess in action.

Best of luck to all participants!

UPD 1: We’ve made a few minor corrections and clarifications to the task descriptions to ensure everything is as clear and transparent as possible. Full list of changes: https://github.com/ton-studio/tact-smart-battle/pull/1
If you’ve already started working on your solutions — take a quick look to make sure your task wasn’t affected. The logic remains unchanged; the updates are purely textual.

UPD 2: We’re aware that some participants have explored ways to pass the tests without fully implementing all the requirements stated in the task descriptions. That’s on us — some test cases didn’t cover all possible edge scenarios, and we appreciate your creativity in finding those gaps.
That said, we confirm the following: final score will be determined solely based on the results of the available test cases. Your position on the leaderboard directly reflects the number of points earned through passing these tests. This decision ensures transparency and fairness for all participants.
Important: this does not exempt submissions from checks for plagiarism and independent work. Any violations in that regard may still result in disqualification.

Thank you to everyone who’s competing honestly and helping make this format better. You are the core of this community.

Hello Codeforces! This Saturday, the student final of BSUIR Open XIII will take place, accompanied by rounds Codeforces Round 1021 (Div. 1) and Codeforces Round 1021 (Div. 2) at Apr/26/2025 11:35 (Moscow time), featuring problems from this competition. Note the unusual time of the round.

This year, the problems for the rounds and the olympiad were prepared by teraqqq, FairyWinx, Kirill22, and wilcot. Each round will contain 6 problems, and you will have 3 hours to solve them. Notably, wilcot has been contributing problems to BSUIR Open for multiple years and has helped involve new authors in this event. We believe this effort has resulted in a diverse and exciting student final, part of which has been adapted into this Codeforces round.

We extend our special thanks to MikeMirzayanov, geranazavr555, and KAN for the fantastic Polygon and Codeforces platforms! We also thank:

• Artyom123 for coordinating the round and recruiting testers;
• arvindf232, A_G, N_z__, jtrh, __jk__, reirugan, and larush for testing the round;
• Golovanov399, SomethingNew, allvik66, golikovnik, and OG_Matveychick1 for testing the BSUIR Open problems;
• i_love_gold_and_nt and Gornak40 for their help in preparing the problem statements.

Special thanks to the people who made BSUIR Open XIII possible:

• Velikovich Vladimir, Shved Elizaveta, Vnuk Olga, Yurchenko Olga, Gorokh Andrey, Makarevich Darya, and Sevryukov Stepan for organizing the championship;
• Udovin wilcot Ivan, Markovets Roman, Baitasov Rinat, Romashevsky German, Butoma Vitaly, Lyubashenko Andrey, and Sitnikov Alexey for preparing the semifinal problems;
• Yefimchyk Alexander and Adarov Dmitry for technical support of the championship.

For yet another year, the BSUIR Open championship has taken place within the walls of BSUIR. Each time, the organizers bring something new, unique, and unforgettable. Thanks to them, BSUIR Open continues to delight participants with its friendly atmosphere, engaging problems, and wonderful prizes!

UPD. The score distribution is:

Div 2: $$$500 + 1250 + 1500 + 2250 + 2750 + 3250$$$

Div 1: $$$500 + 1000 + 1500 + 2000 + 3000 + 3500$$$

UPD2: Editorial

cry and I are very very very excited to invite you to participate in Codeforces Round 1020 (Div. 3), which will take place on Apr/24/2025 17:35 (Moscow time). You will be given 7 problems and 2 hours & 15 minutes to solve them. There will be at least one interactive problem, so please make sure to read this guide if you are not familiar with the format. One of the problems will be split into two subtasks.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of 10 minutes for each wrong submission, following the rules of educational rounds.

Remind yourself 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)
• 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).

Also, note the rule restricting the use of AI. If you are caught while breaking this rule, you will be terminated and haunted. So for your own safety, please do adhere to this rule.

This round would really not be possible without the help of the following people:

• cry for coordinating the round and being kind enough to offer a problem for the set and Vladosiya for statement translation;
• cowthecow and rangerscowboys for their initial contribution to the problemset with unused and impossible problems;
• the non finite amount of testers: Dominater069, Intellegent, -firefly-, Proof_by_QED, __baozii__, Edeeva, Timosh, Friedrich, reirugan, yoru_sacri, IceWolf898, rangerscowboys, rewhile, chromate00, RE_Prince, Furyna, Banis, pop, beaten_by_ai, pianapolataa, Ashrayy, cowthecow, macaquedev, larush, ETL, bricked_, sbreger60, Lapca5, and other people from cry's basement;
• MikeMirzayanov for the amazing Polygon & Codeforces platforms;
• You for participating.

I hope to see you in the contest, and that you will be an honest and fair participant.

UPD: Editorial

UPD2: Winners!

All participants:

1. Hamed_Ghaffari

2. maspy

3. TKT_YI

4. BurnedChicken

5. DevastatingStrike

Trusted & Rated participants:

1. iren_eustia

2. tarunnnnn

3. alyzha

4. nan1669

5. CR7MEN7ALI7Y