Hello, Codeforces!

We are pleased to announce the resumption of the Global Rounds. Thanks to XTX Markets for supporting the initiative! In 2024, we will hold 4 such rounds. The series results will take into account the best 3 participations out of 4.

On Oct/27/2024 17:35 (Moscow time) we will host Codeforces Global Round 27.

Codeforces Global Round 27 marks the third round in the 2024 series of Codeforces Global Rounds. These rounds are open and rated for everyone.

The prizes for this round are as follows:

• The top 30 participants will receive a t-shirt.
• 20 t-shirts will be randomly distributed among participants ranked between 31 and 500, inclusive.

The prizes for the 4-round series in 2024:

• In each round, the top-100 participants get points according to the table.
• A participant's final score will be the sum of the points they earned in their 3 highest-placing rounds.
• The top 20 participants across the series will receive sweatshirts and placement certificates.

We extend our gratitude to XTX Markets for supporting the global rounds initiative in 2024!

The 8 problems were authored by our 8 authors: Benq, lunchbox, oursaco, sum, willy108, Hori, turtletortles, and last but not least ChatGPT.

We would also like to thank:

• Our coordinatorz Sugar_fan (first time) and errorgorn (almost last time)
• Our testers jqdai0815, SSerxhs, RDDCCD, wygzgyw, fallleaves01, triple__a, tarjen, omeganot, Yam, InternetPerson10, EmeraldBlock, Cai_Guang, Tobo, jay_jayjay, Nanani, ezraft, myst-6, Mr.Pie, AbduSaber, A_Nafees, Timosh, redpanda, newb_programmer, Jasonwei08, koolkid403, ShineChang318, khluo
• Alexdat2000 for translating the statements to Russian
• the one and only KAN
• MikeMirzayanov for creating the Codeforces platform

Round Information:

• Duration: 180 minutes
• Number of problems: 8 problems with 1 subtask
• Score distribution: 250 — 500 — 1000 — 1500 — 2000 — 2250 — (2250 — 2000) — 4500

We look forward to your participation!

UPD: Congrats to the winners

1. Kevin114514
2. 275307894a
3. jiangly
4. JoesSR
5. ksun48
6. turmax
7. dXqwq
8. hos.lyric
9. Rewinding
10. jiangbowen

UPD2: First solves

A: dXqwq
B: hos.lyric
C: dorijanlendvaj
D: riantkb
E: turmax
F: taeyeon_ss
G1: taeyeon_ss
G2: Kevin114514
H: orz (only in contest solve!)

UPD3: Editorial

Hello Codeforces! Me and yud08 are excited to invite you to take part in Codeforces Round 982 (Div. 2), which starts on Oct/26/2024 17:35 (Moscow time). You will be given 5 problems and 2 hours to solve them. Two problems are divided into two subtasks.

This round will be rated for all participants whose rating is strictly below 2100.

The problems were authored by me and yud08, and prepared by me.

We would like to thank:

• abc864197532 and Vladithur for an amazing double coordination.
• Alexdat2000 for translating the statements to Russian.
• BurnedChicken for LGM testing.
• BucketPotato, Fysty, alvingogo, and WiwiHo for red testing.
• sammyuri, anango, jay_jayjay, amsraman, Intellegent, valeriu, erekle, and golions for orange testing.
• Beacon, iceylemon157, and LittlePants for purple testing.
• Jasonwei08, godgenji, Banis, temmieowo and Arthas for blue testing.
• t0rtik, lumid, and AG-88301 for cyan testing.
• vatzahellmen for green testing.
• MikeMirzayanov for the Polygon and Codeforces platforms.

We hope you enjoy the problems!

Score Distribution: $$$500 - 1000 - 1250 - (1250 + 1000) - (2000 + 1000)$$$

We actually wanted to continue the trend of posting photos of contest writers, but we could only find one photo containing both of us, which was a group photo that we took with some other UK informatics people! (I'm the one in the back of the picture who is wearing the MHC T-shirt and yud08 is the one whose head is popping out from the left side of the photo.)

UPD1: Congratulations to the winners of the contests:

Div 1:

1. jiangly
2. neal
3. SSerxhs
4. A_G
5. kotatsugame

Div 2:

1. nathan_higgs
2. purupurupururin
3. Nonoze
4. Hong_Meiling
5. Nika_Tamliani

Also, first solves! (if any of these are wrong please let me know)

• A: A_G in 00:00:45
• B: A_G in 00:03:01
• C: Alex239 in 00:05:09
• D1: 74TrAkToR in 00:09:21
• D2: 74TrAkToR in 00:18:51
• E1: jiangly in 00:38:36
• E2: jiangly in 01:01:08

UPD2: Editorial is available here

Hello Codeforces!

I am pleased to invite you all to participate in Codeforces Round 981 (Div. 3), which will start on Oct/24/2024 17:35 (Moscow time).

The format of the event will be like any Div. 3 rounds:

• 6-8 tasks;

• ICPC rules with a penalty of 10 minutes for an incorrect submission;

• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)

• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated

• by default, only "trusted" participants are shown in the results table.

I encourage participants with a rating of 1600+ not to create new accounts but to participate unofficially.

Only trusted participants of the third division will be included in the official standings table. This is a forced 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 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 (or you are a newcomer/unrated), then the round will be rated for you.

Also, it will be a round with unrated register. If you already registered as rated participant you can change registration type here.

I would like to thank

• MikeMirzayanov for creating Codeforces and Polygon.

• Vladosiya for beautiful coordination and helping in preparation.

• Pa_sha, SashaT9 and Skillful_Wanderer for not only testing but also discussion of the problems.

• Hyperbolic, Irmuun.Ch for red testing.

• LMeyling, Sokol080808, Intellegent, 18o3, amoeba3, -1e11, Error_Yuan, Wandoka for yellow testing.

• wuhudsm, Viktor36, CarlosS48 for purple testing.

• adepteXiao, yellow_13, macaquedev, Pa_sha, Vinayak286, chromate00 for blue testing.

• darysani for cyan testing.

• Parag_AP for green testing.

• My friends cat Chefir who inspired one of the task statements

Good luck!

Upd: Editorial is out.

Hello, Codeforces! We're glad to invite you to take part in Codeforces Round 980 (Div.1, Div. 2), which will start on Oct/20/2024 12:05 (Moscow time). Note the unusual time of the round. Each division will have 6 problems and 2 hours to solve them. The round will be held according to the Codeforces rules and will be rated for both divisions.

The problems were authored and prepared by Mangooste, Tikhon228, adepteXiao, Artyom123, sevlll777, yunetive29, glebustim, Endagorion, isaf27 guided by Ormlis and Helen Andreeva.

The round is based on XXII Moscow Team Olympiad, high school students competition based in Moscow that is an elimination contest for All-Russian Team Olympiad. Also thanks to the authors of the Olympiad whose problems were not included in the round : vaaven, TeaTime, pakhomovee, TheEvilBird, ch_egor.

We would like to thank specially:

• Artyom123 for his high-speed coordination.
• MikeMirzayanov for creating Codeforces and Polygon.

Great thanks to the testers: Kapt, SomethingNew, k1sara, Pekiban, automac, theRealChainman, marks39, cosenza, pengin_2000, Killever, perchuts, Endagorion, maomao90.

As well as the teams testing the main Olympiad: (RP-1, kostylevGO, PBBx0), (AgafonovArtem, blyat), (daubi, talant, alexxela12345), (tem_shett, crazyilian, sevlll777), (katyaporay, Igorbunov, Dart-Xeyter), Kirill22, (rama798, FlameDragon, egneeS), (MOHOXPOM, Goshix, shevnin_d), teraqqq, (Siberian, Um_nik), (kova1, Aleks5d), (makcvim, Silver_Fox), polosatic.

UPD1: Score distribution:

Div.2: 500 — 1000 — 1250 — 1750 — 2250 — 3000

Div.1: 500 — 1000 — 1500 — 2250 — 2750 — 3000

UPD2: Due to the official competition source codes of other participants will not be available for two hours after the end of the round.

UPD3: Editorial

Haiii Codeforces ^_^

Note the unusual starting time. This round starts 30 minutes before the standard starting time.

vgoofficial and I are extremely excited to invite you to Codeforces Round 979 (Div. 2) on Oct/19/2024 17:05 (Moscow time). You will be given 7 problems and 2 hours and 15 minutes to solve them. One problem will be split into two subtasks. This round will be rated for all participants with rating below 2100.

This round is based on... absolutely nothing.

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

• Our coordinatorz satyam343 for his active and insightful coordination once again. ORZ!!!!

• Our testuwuwuwuers for their efforts in improving this gramazing contest: nifeshe (VIP tester), Thienu, Anonymous_Noob, Dominater069, A_G, Everule, LipArcanjo, omeganot, MridulAhi, 18o3, Edeeva, IceKnight1093, andrewtam, JagguBandar, LMeyling, Intellegent, valeriu, aryanc403, awesomeguy856, kingmessi, amoeba3, golions, unalive, alexlikemath007, fishy15, Vladosiya, NovusStellachan, CutSandstone, chromate00, ntarsis30, Non-origination, redpanda, Lilypad, kevlu8, MatthewC3297, mathtsai, jcai972, and our honorary newbie tester tibinyte.

• Alexdat2000 for translating the statements to Russian.

• The most jacked user on this list, MikeMirzayanov, for developing Codeforces and Polygon.

Score Distribution: $$$250 - 500 - 1000 - 1500 - 2000 - 2500 - (3000 + 1500)$$$

UPD: Editorial

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos. They offer a BSc in Computer Science and AI with JetBrains Scholarships. Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Curious? Check out the CSAI curriculum now. Limited scholarships available — don't miss your chance to study in Europe for free!

Are you looking to sharpen your skills and increase your chances of getting a scholarship? Join the free clubs for high school students from JetBrains:

• Math club
• AI club
• Coding club

On Oct/14/2024 17:35 (Moscow time) Educational Codeforces Round 170 (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, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Aleksandr fcspartakm Frolov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Please note that the problems of this round partially intersect with the problems of the Qualification stage of the Southern and Volga Russian Regional Contest. If you took part in the qualification, please refrain from participating in the round.

Good luck to all the participants!

UPD: Editorial is out

Hola, Codeforces!

We're glad to invite you to take part in Codeforces Round 978 (Div. 2), which will start on Oct/13/2024 22:35 (Moscow time). You will be given 5 problems and 2 hours to solve them. Some problems will be divided into subtasks.

This round is based on day two of the Mexican Olympiad in Informatics (OMI) 2024.

Please note the unusual starting time.

The team of writers is conformed by JuanPabloAmezcua, SebR, Marckess, and myself. We have spent a ton of effort setting the round as well as the Olympiad, we hope you enjoy it.

(This is our logo, cookie points if you can guess the names of the two characters in it)

The team would like to thank:

• errorgorn for the most based coordination. The round exists thanks to him, the team loves you sir.

• All the testers for their support and great feedback: blackyuki, Dominater069, frodakcin, bashkort, wyrqwq, prvocislo, Umi, MeGustaElArroz23, Ari, gxlois, Error_Yuan,_rey, LoboLobo, maomao90, oursaco, willy108, fishy15, AlperenT, JoenPoenMan, Skywk, ozy1220, Daniel19Frenzy, nyaruhodo, OmarFaridAM, karlamun, biank, alexbrii, El_Roge, SpecterByte, dazlersan1, juanbrau.or, HerreraDaniel, saultapiaprogra, viktorchares, mafflopez, tibinyte, zesty, RasecBadguy

• Alexdat2000 for translating statements.

• KAN for believing in the project.

• ocarima the godfather of the Mexican Olympiad in Informatics, for believing in us, all his support and pushing us to grow.

• MikeMirzayanov for creating codeforces, and sorry but I have to say this, the amazing system Polygon.

Score distribution: 750 + 1000 + 1750 + (1750 + 2000) + (2250 + 1000)

We wish you happy coding and good luck to all participants!

Winners Div 1:

1. tourist
2. ecnerwala
3. neal
4. maspy
5. 244mhq

Winners Div 2:

1. tko919
2. thanos_2
3. moonpole
4. vgoofficial
5. hashman

First solve for each problem:

• A:sololtin2001
• B:it.shivam
• C:tourist
• D1:jdurie
• D2:tourist
• E1:rainboy
• E2:rainboy

UPD 1: We have added new testers and score distribution.

UPD 2: There is at least one interactive problem, so please read the guide for interactive problems if you are unfamiliar with them.

UPD 3: The editorial is ready. Congratulations to the winners and first solves for each problem!

Hi everyone!

I'm posting this on behalf of CP-Algorithms, a community project that started off in 2014 by RodionGork as a translation of e-maxx, a Russian go-to resource at the time by e-maxx for learning core competitive programming algorithms. Since then, CP-Algorithms grew quite a lot (which also prompted a rename from original project name e-maxx-eng) and includes a lot of new, original articles, and a lot of translated articles were enhanced and/or extended or even completely rewritten, amounting to a total of 157 articles at the moment.

At the moment, the project is largely maintained by Jakube and adamant (that's me), but as it happens, we don't have as much time to dedicate to it as we used to, so we're looking for some fresh blood to join the effort. This means both potential contributors and maintainers.

Contributors

As a community project, it is largely driven by volunteering efforts of people who write and translate articles. Moreover, similar to previous years, right about now DigitalOcean is conducting Hacktoberfest, an initiative that will award every participant which will make 4 approved pull requests on Github (in participating projects) during the month of October with a cool, free shirt

UPD: sorry, it's just a digital badge on holopin instead of t-shirts starting last year ☹️

Our project participates in Hacktoberfest, so it could be an easy way for you to contribute into open source and get a t-shirt for it. Not sure what to help us with? Consider the following:

• GitHub issues marked with "bug" or "enhancement" tags;
• Translation progress indicates which articles still need to be translated;
• Write a new article on the topic of your liking or from a "new-article-suggestion" tags in GitHub issues;
• Improve old articles (fix typos, grammar, style, etc);
• Add images (make sure they're your original work, or adhere to image's license!).

See How to Contribute page for some instructions, or just click on a pencil icon in the upper-right corner of any article to propose changes. You can also use the Article Preview page to see how your changes will look like when they're actually added to the site. If you still have any questions about the process, don't hesitate to reach out to me directly 😊

Maintainers

Besides regular contributors, we're in dire need of having more people joining the maintainer team. You would be granted a right to contribute to the project directly without prior approval, and will need to exercise it appropriately, both when making your own contributions and when reviewing open issues and pull requests that you will be able to merge into the main branch once you think they're good enough.

On top of it, some time ago I started out a competitive programming library with automatic verification via Library Checker as an auxiliary project to CP-Algorithms. Ideally, I would like to let more people join it in the future, and also facilitate its integration into the main website and its articles somehow. Having another motivated maintainer to discuss it and work on it together would be fantastic!

Please reach out to me or Jakob if you're interested, and let us know of any of your prior experience in technical writing, computer science and competitive programming. We will be happy to expand our team!

Hello Codeforces!


We are delighted to invite you to participate in Yandex Cup 2024!
Yandex Cup is a championship in six different tracks:

• Algorithm❤️
• Backend
• Analytics
• Mobile development (iOS and Android tracks)
• Frontend
• Machine Learning (Self-Driving Cars and Music information retrieval tracks)

This year, as a pilot project, we are inviting schoolchildren (so far only from Russia) to participate in the Algorithm and Analytics tracks.


The championship consists of three stages.

Schedule

The stages and dates are different for Machine Learning and Mobile Development. More details about the terms and conditions can be found on the track's pages.

Qualification is a contest with a virtual start. You can write a context during the week from 14 to 20 October. The duration depends on the selected track. After the qualification stage we will publish the criteria for the semifinal.

Semifinal will be held on 3 November. The start of the contests is at 12:00 (GMT+3) and at 17:00(GMT+3) at the Algorithm track. Duration depends on the selected track. The top 20 semi-finalists in each track and the top 10 students in the tracks Algorithm and Analytics will qualify for the finals

The final of the competition will be held in Tashkent Uzbekistan on 2-6 December. All expenses related to travel and accommodation of the finalists will be covered by us.

This year, we have also increased the prize fund, which amounts to 12.5 million rubles

See you at the Yandex Cup!

Halo, Codeforces! Ape kabar kitak? Nyi deu sit bau maang? 😍 😍

COMPFEST 16 is happy to invite you to participate in Codeforces Round 977 (Div. 2, based on COMPFEST 16 - Final Round) on Oct/06/2024 09:05 (Moscow time). The round will be rated. You will be given 2 hours to solve 5 problems, 2 of them will have subtasks.

Note the unusual time of the round.

The problems are written by ArvinCiu, CyberSleeper, athin, and joelgun14.

We would like to thank:

• KAN for helping to host the round;
• errorgorn for the based coordination;
• gansixeneh, CyberSleeper, joelgun14, and icebear30 for helping with the problem preparation;
• gansixeneh again for the sigma helps;
• Alexdat2000 for writing the Russian translations;
• A_G, Dominater069, efishel, Error_Yuan, fishy15, Sk0rlupka, Umi and valeriu for testing the contest and providing us very useful feedback;
• Universitas Indonesia, all the local committees, administrators, and managers of the whole COMPFEST event;
• MikeMirzayanov for the amazing Codeforces and Polygon platform!

COMPFEST itself is an annual event hosted by Universitas Indonesia. It is the largest student-run IT event in Indonesia and competitive programming contest is one of the competitions hosted.

We hope you will enjoy and have fun in the contest. Muga-muga beja lan isa entuk biji apik!! 💪💪🔥🔥

Edit 1: Score distribution is $$$500 - 750 - (750+1000) - 2500 - (1750 + 750 + 1000)$$$

Edit 2:

Congratulations to the winners!

Div.2 :

1. Xun_Xiaoyao

2. Traumatize

3. TurtleZW

4. wullaaa

5. cpy0512

Div.1 + Div.2:

1. ecnerwala

2. tourist

3. ksun48

4. StarSilk

5. kotatsugame

Congratulations also to the first solvers!

• A: _MASSIMO_

• B: iridescent24k

• C1: ksun48

• C2: 2mato_pota2

• D: ecnerwala

• E1: vlt0824

• E2: nifeshe

• E3: xuanxuan001

On behalf of the COMPFEST committees, we are glad that our Codeforces Round ran quite smoothly and we hope that you all enjoyed our problems. See you next year! 😍 😍

Edit 3: The editorial is up!