By MikeMirzayanov, 4 weeks ago, translation, In English


ICPC Southern and Volga Russian Regional Contest (Northern Eurasia) 2020 has ended on November 15. This year the competition took place online. 108 teams competed, many of them received an invitation based on the results in Qualification Contest.

On Dec/25/2020 14:35 (Moscow time) will start online-mirror 2020-2021 ICPC, NERC, Southern and Volga Russian Regional Contest (Online Mirror, ICPC Rules).

Hope you enjoy the problems. In this contest I play a role of Cheif Judge and the jury teams consists of ex-participants of ICPC from Saratov and jury members from other cities: adedalic, I_Remember_Olya_ashmelev, BledDest, DmitryKlenov, DStepanenko, elena, KAN, kuviman, MikeMirzayanov, pashka, PavelKunyavskiy, Дмитрий Мещеряков, Герман Наркайтис. Many thanks to all of them!

I send special rays of gratitude to testers: Merkurev, Um_nik, romanasa, josdas, Nebuchadnezzar, Perforator, Oleg_Smirnov, IlyaLos, Supermagzzz, Stepavly, Igor_Kudryashov, HolkinPV, Edvard, le.mur!

I invite ICPC teams and individual participants of Codeforces competitions to take part!

Of course, the competition will be unrated. I ask the participants of the official competition to refrain from participating in the mirror and discussing problems until its end.

Since this year the audience of participants was wider (due to the online format), we also selected problems a little more accessible than in previous years. If you are from the top team that claims a medal in the ICPC Finals, then it may be more fun for you to take part in this contest personally.

Good luck!

Read more »

  • Vote: I like it
  • +269
  • Vote: I do not like it

By dargelirli, history, 5 weeks ago, translation, In English

Hi all!

This weekend, at Dec/20/2020 18:05 (Moscow time) we will hold Codeforces Round 692. It is based on problems of Technocup 2021 Elimination Round 3 that will be held at the same time.

Technocup is a major olympiad for Russian-speaking high-school students, so if you fall into this category, please register at Technocup 2021 website and take part in the Elimination Round.

Div. 1 and Div.2 editions are open and rated for everyone. Register and enjoy the contests!

The Elimination Round authors are neckbotov and dargelirli. Thanks to Nebuchadnezzar and KAN for their coordination. Also huge thanks to testers for their invaluable help: isaf27, 300iq, Kaban-5, low_, Shinchan01, wiwitrifai, Ashishgup, spar5h, Nemo, Gauravvv, Vax, XLor, Um_nik, ADJA, jiufeng, RobeZH, Daryusz, antontrygubO_o, Normie28, rkm62, gratus907, Manik!

Have fun!

Elimination Round will feature 7 problems, preliminary costs are
500 — 1000 — 1750 — 2000 — 2250 — 2750 — 3250.

Div. 2 will feature 6 problems, preliminary costs are
500 — 1000 — 1750 — 2000 — 2250 — 2750.

Div. 1 will feature 6 problems, preliminary costs are
750 — 1000 — 1250 — 1750 — 2250 — 3000.

The analysis is published.

The round is over, congratulations to the winners!

Technocup 2021 - Elimination Round 3

  1. almogwald
  2. serg3000
  3. Pechalka
  4. denisrtyhb
  5. 777

Codeforces Round #692 (Div. 1, based on Technocup 2021 Elimination Round 3)

  1. EricHuang2003
  2. jiangly
  3. hos.lyric
  4. ecnerwala
  5. ugly2333

Codeforces Round #692 (Div. 2, based on Technocup 2021 Elimination Round 3)

  1. KanbeKotori
  2. xmt
  3. RNG-Ming
  4. YANK01
  5. Kalecgos

Read more »

  • Vote: I like it
  • +295
  • Vote: I do not like it

By Endagorion, history, 5 weeks ago, In English

Hello, Codeforces community!

I'm glad to invite you to Codeforces Round #691 (Div. 1) and Codeforces Round #691 (Div. 2), which will be held on 19.12.2020 12:35 (Московское время). The round will be rated for both divisions.

The problems were taken (mostly) from the ByteDance — Moscow Workshops Online Contest, which is happening at the same time. They were prepared by me, AndreySergunin, and amethyst0. We are very thankful to the testers: low_, rkm62, ecnerwala, Tima, IITianUG, thenymphsofdelphi, mohammedehab2002, namanbansal013, Redux for their time and great feedback. Also big thanks to Bytedance instructors chenjb and Retired_MiFaFaOvO for testing and reviewing the Bytedance online contest.

ByteDance is a global technology company operating a range of platforms that allow people across languages, cultures and geographies to create, discover and connect. ByteDance has partnered with Moscow Workshops and Codeforces to organize a top tier and exclusive training camp for the International Collegiate Programming Contest. The upcoming Programming Camp will be held in Beijing from February 20th to 26th, 2021.

ByteDance — Moscow Workshops Online Contest is an opportunity to participate as teams in this camp.

You can find more information about this training camp, including registration and prizes at

Important update: please be informed that the Bytedance online team contest ends 25 minutes after the Codeforces round does. For this reason, we ask you not to discuss the problems publicly during that time, until 3pm MSK. Code and testcases public display will also be disabled during that time. Thank you for your understanding.

Scoring distribution:

Div. 2: 750-1000-1500-2000-2500-3000

Div. 1: 500-1000-1500-2000-2250-3500

Final update: thanks for participating, hope you had fun! Let's hear it for the winners:

Div. 1 (the only contestants to solve 5 problems):

  1. tourist
  2. Um_nik
  3. 142857
  4. maroonrk
  5. DmitryGrigorev

Div. 2:

  1. spepd — the only Div.2 contestant to solve 5 problems!
  2. LebronDurant
  3. diuven_fanclub
  4. 1004535809
  5. CTP_314

Here's a (now complete) editorial.

Happy winter holidays to all of you, and see you again on the leaderboards!

Read more »

  • Vote: I like it
  • +492
  • Vote: I do not like it

By awoo, history, 5 weeks ago, translation, In English

Hello Codeforces!

On Dec/17/2020 17:35 (Moscow time) Educational Codeforces Round 100 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

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 Roms Glazov, Adilbek adedalic Dalabaev, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Also thanks to Nikolay KAN Kalinin for one of the problems' ideas.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

Codeforces and Harbour.Space

Hey Codeforces!

It’s almost the Holiday season, and this year, we have an extra reason to celebrate — this December marks Harbour.Space’s 5-year anniversary!

Looking back, we’re especially thankful for the wonderful partnerships that have made our university what it is today.

Codeforces has been one of our key partners since the beginning, and we would like to thank the community for growing with us for the past 5 years.

You guys are rock stars, and we’re excited to see where the future takes us both.

Harbour.Space University

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 heno239 6 174
2 Geothermal 6 178
3 stevenkplus 6 238
4 hank55663 5 87
5 neal 5 121

Congratulations to the best hackers:

Rank Competitor Hack Count
1 3.141592653 49:-3
2 sheaf 48:-17
3 adnan_toky 32:-2
4 _Backl1ght 30:-2
5 star_xingchen_c 27:-1
1083 successful hacks and 1034 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A I_love_Anya_Prokopyeva 0:01
B MikMirzoyanov 0:03
C Geothermal 0:11
D peti1234 0:06
E CoderAnshu 0:23
F heno239 1:13

UPD: Editorial is out

Read more »

  • Vote: I like it
  • +422
  • Vote: I do not like it

By Supermagzzz, history, 5 weeks ago, translation, In English

Hello, Codeforces!


Hello! Codeforces Round #690 (Div. 3) will start at Dec/15/2020 17:35 (Moscow time). You will be offered 6 problems (one of them is split into two subtasks) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 problems and 2 hours to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.

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 trusted participants of the third division, you must:

  • take part in at least two rated rounds (and solve at least one problem in each of them),
  • do not have a point of 1900 or higher in the rating.

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.

The problems for this round were invented by MikeMirzayanov and prepared by me Supermagzzz and Stepavly

Thanks to MikeMirzayanov for platforms and coordination of our work. Thanks to Sho, kocko, brian, Crazy_hedgehog, manta1130, Rox, Gassa for help in round preparation and testing the round.

Good luck!


UPD: Editorial is published

Read more »

  • Vote: I like it
  • +475
  • Vote: I do not like it

By NercNews, 7 weeks ago, In English


Hello everyone!

We are thrilled to invite you to the great event — ICPC NERC Challenge powered by Huawei 12 — 20 December 2020.

Join to Challenge

This contest is based on some real problems from Huawei Cloud team. The task is simplified, but still very challenging. You need to find a schedule for a variety of realistic problem instances, where the goal will be minimizing two different cost functions. There is a non-trivial tradeoff, decision you have to make, on how to choose what is best for a particular case. You will be provided with examples that can help you to tackle the problem. A good solution may also require diving deeper into the nature of the problem, and creating some dataset of your own. We believe there are multiple approaches one can try here, and some crossover of the algorithms will also increase your chances to win. Good luck, we hope this will be fun!

The ICPC NERC Cloud Scheduling Challenge powered by Huawei will take place online during the week of December 12-20. This round is unrated for all participants. Everybody is welcome to participate. It is an individual competition. Participants will be divided into two groups: Northern Eurasia Contestants 2020 (all subregions) and all other Participants. If you are a NERC 2020 contestant and you want to take part in ICPC NERC Challenge, link your ICPC account to the Codeforces account here:


The top-scoring participants will also receive great prizes. Huawei will provide prizes to the 12 winners in both groups accordingly:

  • 1-4th place — HUAWEI P40 PRO
  • 5-8th place — HUAWEI MATEPAD PRO LTE
  • 9-12th place — HUAWEI WATCH GT 2E

In this video Andrey Tikhonov, the co-author of Cloud Scheduling Challenge will explain the basics of the task and describe some special cases and examples:

UPD: ICPC NERC Cloud Scheduling Challenge successfully finished! Thanks all for competing. Congratulations to winners with excellent results! In the video below Andrey Tikhonov will explain the problem solution:

Good luck to all participants!

Read more »

  • Vote: I like it
  • +367
  • Vote: I do not like it

By Vladik, 6 weeks ago, translation, In English


Hi Codeforces!

I am glad to announce and invite you to Codeforces Round #689 (Div. 2, based on Zed Code Competition), which will be held on Dec/11/2020 17:35 (Moscow time).

We want to offer you to solve 6 problems taken from the Zed Code Competition 2020, which was held as part of the Adapt by Zed conference powered by EPAM Systems.

This round will be rated for the participants with rating lower than 2100.

Thanks a lot for your contribution to the preparation of the round! Good luck with the competition!

UPD: The scoring distribution is 500 — 1000 — 1250 — 1500 — 2250 — 2750.

Congratulations to the winners of div 2:

  1. yash_daga
  2. AiriKatagiri
  3. tejas10p
  4. RNG-Ming
  5. Kalecgos

as well as div 1 winners:

  1. neal
  2. Geothermal
  3. LayCurse
  4. emthrm
  5. hank55663

Thank you all for participating! (editorial)

Read more »

  • Vote: I like it
  • +328
  • Vote: I do not like it

By MikeMirzayanov, 6 weeks ago, In English

In 2020, with the support of XTX Markets, 6 rounds of the Codeforces Global Rounds were held. Each round was common for both divisions. All such rounds were rated for all participants. At each such round, 50 brand T-shirts were handed out, and we gave T-shirts to all problem writers!

I say a big thank you to XTX Markets (and personally to Yuri Bedny and Alexander Gerko) for supporting Global Rounds. Without your help, we could not host them! I sincerely admire companies like these who come to support and develop the community that some of their employees come from. It will be great if other companies follow the example and also offer their help. We need it!

The prizes for the 6-round series in 2020:

  • In each round, top-100 participants get points according to the table.
  • 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.

Final results (and congratulations!):

Read more »

  • Vote: I like it
  • +317
  • Vote: I do not like it

By kuviman, 6 weeks ago, In English

Hello everyone!

AI Cup 2020 — the annual artificial intelligence programming championship by Mail.Ru Group is already running.

AI Cup — open artificial intelligence programming contest. Test yourself writing a game strategy! It’s simple, clear and fun!

This year's theme is — RTS. We are waiting for you on our site! The site is already open, you can start implementing your strategies.

Ninth AI Cup championship is named CodeCraft. You are to program an artificial intelligence to control a number of units, gather resources, build your settlement and attack your enemies. Your strategies will compete with each other in the Sandbox and the championship. Currently availiable programming languages: C++, C#, F#, D, Go, Java, Kotlin, Scala, Python, Rust. The Sandbox is already open. Good luck!


  • Sandbox: already open for everyone.
  • Round 1: December 12-13.
  • Round 2: December 19-20.
  • Finals: December 26-28.


In the past years, the winners have received prizes, like MacBooks, iPads, watches and hard drives. In addition, we presented 60 hoodies and 360 T-shirts.

Unfortunately, the participants of the previous AI Cup received T-shirts only almost a year later (we delivered the prizes). In a pandemic, we were powerless and not ready.

In this regard, we thought to cancel the merch in this competition, but a the community did not receive this news well. “No promo codes or other virtual prizes needed, we need T-shirts and hoodies” — quote from the community.

Change 1: the prizes are now not physical, but cash. This year's winners will receive:

  • 1st place — 250,000 rubles (about $3364).
  • 2nd place — 200,000 rubles (about $2691).
  • 3rd place — 150,000 rubles (about $2018).
  • 4th place — 125,000 rubles (about $1682).
  • 5th place — 100,000 rubles (about $1345).
  • 6th place — 75,000 rubles (about $1009).

Sandbox winners (also 6 people) will receive 10,000 rubles each (about $135). Amounts are after taxes. We have significantly increased the prize pool.

Change 2: T-shirts and hoodies will be available, but delivery will not be until February. If you don't want to wait, you can exchange your promotional gift for a promotional code in Group services (cloud, etc.).

All participants in Round 2 will receive T-shirts, and the finalists will receive hoodies.

Begin from the Quick start guide. Writing a simple strategy is not hard at all!

Read more »

  • Vote: I like it
  • +153
  • Vote: I do not like it