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 2 November. The start of the contests is at 12:00 (GMT+3). 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!

Greetings Codeforces!

First things first, we would like to thank everyone who participated in the previous nine Kotlin Heroes competitions: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, Episode 8, Episode 9, and Episode 10.

Kotlin Heroes is a great way to play around with Kotlin’s features, learn something new, and practice using the language by solving fun problems. It is great for programmers of any level!

We invite you to join the practice round, where you can improve your algorithmic problem-solving skills and complete training problems. In this round, all the solutions are open and you can request hints if you’re stuck.

Watch tourist and ecnerwala tackle the Kotlin Heroes practice round challenges at the ICPC World Finals in Astana.

Here are some things you can do to help you refresh your knowledge of Kotlin and learn more about competitive programming while you practice:

• Review our Kotlin solutions for the Advent of Code algorithmic puzzles.
• Read our competitive programming tutorial.
• Watch the videos from our Kotlin in Competitive Programming YouTube playlist.
• Look at the problems from the previous practice rounds.

On September 30, 2024, the real challenge begins! Kotlin Heroes: Episode 11 will last 2 hours 30 minutes and will feature a set of problems ranging from simple ones, which are designed to be solvable by anyone, to some really tricky ones for seasoned competitive programmers.

Note that the usage of AI-based tools during the main contest is strictly limited. To find out the guidelines for proper AI use, what is allowed and what is prohibited, please read the post "Rule Restricting the use of AI". Improper use of AI tools during the main contest may result in disqualification.

Using automatic translation tools (including but not limited to neural networks and AI) to convert code written in other programming languages to Kotlin goes against the spirit of the competition, so it is also strictly prohibited.

Prizes:

The top three winners will receive cash prizes of $512, $256, and $128 (or rewards of equivalent value), respectively. The top 50 participants will win a Kotlin Heroes T-shirt and an exclusive Kotlin sticker, and all competitors who solve at least one problem will be entered into a raffle for one of 50 Kotlin Heroes T-shirts.

Please note that we are not able to ship prizes to any country, state, province, or territory subject to comprehensive OFAC sanctions, including Belarus, Cuba, Iran, North Korea, Russia, Syria, or the Crimea, Donetsk, or Luhansk regions. To see the list of sanctioned countries and regions, please visit this page.

Best of luck to everyone!

Hello Codeforces!

We are thrilled to invite you to participate in Codeforces Round 976 (Div. 2) and Divide By Zero 9.0, hosted as Divide By Zero 9.0 by The Programming Club, Indian Institute of Technology Indore (IIT Indore). The contest will take place on Sep/29/2024 18:35 (Moscow time).

UPD: The contest time has been updated to Sep/29/2024 18:35 (Moscow time), which differs from the previously announced schedule. Please take note of this unusual timing and adjust your plans accordingly.

You will have 2 hours to solve 6 exciting problems.

The round will be rated for participants with a rating below 2100.

Problem Setters:

The problems for this round have been authored by nishkarsh and me.

Acknowledgements:

We would like to extend our heartfelt thanks to:

• irkstepanov and KAN for the wonderful coordination and support in preparing the contest.

• Golovanov399, wyrqwq, irkstepanov, Error_Yuan, rolandpetrean, magga, mwen, MrDelrus, letsolum, chromate00, and AnanasClassic for their valuable feedback and testing.

• Special thanks to MikeMirzayanov for the amazing Codeforces and Polygon platforms.

Score Distribution (Div. 2):

• 500 — 750 — 1250 — 1500 — 2000 — 2750

We hope you enjoy the problem set and have a great time solving!

Good luck to all participants!

Update: The editorial is here

Ciao, Codeforces! We're glad to invite you to take part in Codeforces Round 975 (Div. 1) and Codeforces Round 975 (Div. 2), which will start on 27.09.2024 16:35 (Московское время). You will be given 6 problems and 2 hours and 30 minutes to solve them in both divisions. Some problems will be divided into subtasks.

UPD: the time has been changed to 27.09.2024 16:35 (Московское время), which is different from the time announced before. Please note the unusual starting time.

This round is based on Italian Olympiad in Informatics (OII) 2024.

The problems were authored by lorenzoferrari, wksni and me.

We would like to thank

• KAN for his nutella coordination;
• Alexdat2000 for Russian translation;
• bortoz, collodel, dp_1, franfill, franv, harniver, jamesbamber, Kaey, veluca93, Virv for helping with both this contest and the onsite contest preparation;
• bortoz for pictures in the statements;
• Flamire for VIP testing;
• Um_nik, EgorUlin, konsteros, Mihail_Podyachih, bugrova, Ludissey, Nonoze, Sofapuden, Temmie, jeroenodb for testing;
• MikeMirzayanov for creating Codeforces and Polygon.

Score distribution:

• Div. 1: $$$500 - 750 - 750 - 1500 - (2250 + 750) - (1500 + 1500 + 1500)$$$
• Div. 2: $$$500 - 1000 - 1750 - 2000 - 2000 - 3000$$$

We hope you'll like the problemset!

Update 1: the editorial is here.

Update 2: congratulations to the winners!

TL;DR: Post an interesting Codeforces blog until October 15th and win $800+1.

This blog is inspired by peltorator's Codeforces Month of Blog Posts.

Hi everyone! The last time, this initiative was a gem for me! I've enjoyed every bit of it and the winner in particular — it helped me when I needed it the most. So now I willing to pay back (or forward :D) — by organizing the Codeforces Month of Blog Posts one more time!

Intro

My view is the same as peltorator's one — I am a huge Codeforces fan, it almost replaces me social media, and the blogs section is one of the best parts of it! Many people may be waiting for the best time to publish their blogs — now the time has come!

Rules & Deadlines

The rules are simple:

1. Post something on Codeforces not earlier than 10th of September (00:02 UTC) 2024

We are looking for novel ideas / new views on the topics / tutorials on the topics that we have not seen yet — anything of your choice. It could even be somthing like this comment! — I think you get the idea: write something novel. If I were to judge, one of the best post of the previous peltorator's months was probably his own announcement :D

2. Send me a personal message until 15th of October (00:02 UTC) 2024 with the link to your codeforces blog post

I would appreciate it if you also include a one-sentence explanation at the beginning of your blog post explaining this challenge and a link to the blog post you are reading right now so that more people can learn about it and participate. So the general deadline is 15th of October.

Prizes!

The winner blog post will be awarded with a money prize — $350+1! The runner-up will win $250! The third place will win $150! The forth place will win $50! :)

If you are willing to increase the budget for the winners — also PM me :D

The process of choosing the winner is not decided yet, I may think of two ways: choosing the winner by myself, or the blog post with the most amount of likes. Write your own opinion in the comments sections

Outro

Let the challenge begin! I hope there will be at least one great blog, so my initative won't be left useless :D

801$ is not a small amount — so I believe in you, make something novel, make something that people want!

Maybe we should hold this sort of thing annually? Something like "Codeforces Year of Blog Posts"? Write our ideas in the comments section!

P.S: Check out LI2 Contests!

UPD1: A great friend of mine decided to give an additional $200 for the runner-up! He insisted on remaining anonymous though D:

UPD2: One month left! Additionally, let's thank i_love_penguins for giving a $100 prize for the third place

UPD2: One month left! Additionally, let's thank orz for increasing the budget by $200!

Hello Codeforces!

Greetings from Nottingham, England! We are delighted to invite you to Legend of Robin Hood, a round inspired by our local folklore.

Codeforces Round 974 (Div. 3) will start on Sep/21/2024 17:45 (Moscow time).

You will be offered 6-8 problems 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 of 1600 or higher, can register for the round unofficially.

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.

You will be given 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round 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 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, then the round will be rated for you.

Problems have been prepared by ChairmanFMao, Filikec and RobinFromTheHood.

We would like to thank:

1. Vladosiya for brilliant coordination, and for improving all problems.

2. 18o3, cry, ikrpprppp, pavlekn for orange testing.

3. Axial-Tilted, raztun, vgoofficial for purple testing.

4. Alenochka, FBI, macaquedev, Non-origination, SashaT9, umezo for blue testing.

5. gbula, Pa_sha, 1165MOHITSINGHAL, _Hosam for Div. 3 testing :)

6. MikeMirzayanov for Polygon and Codeforces platforms.

7. You for participating in the round!

Good luck!

UPDATE: Editorial is out!

Image by Zmarlen with our thanks!