Hello!

I always like to think that Codeforces is not only a place where you come to compete but also a place where you can learn. Learn new things.

Two years ago, we launched the EDU subproject, a platform for publishing classes. There are already several classes, but there are so many interesting topics around!

The Codeforces team can write the platform, make the technical foundation, but it would be great to write content with the support of the community.

Thanks to the support of competitive programming alumni, we have a budget for targeted grants for the preparation of new classes in the EDU section. Hope we have new content soon!

We are looking for lesson authors who could prepare and record one or more lessons. Those who are now red or have ever been red are invited.

We assume that one lesson (class) consists of:

• 3-5 steps: break the lesson into logical parts,
• video materials explaining the topic (usually, the total duration is 60-120 minutes),
• text summary
• a thematic training set of problems with a wide range of complexity (from the most basic on this topic to quite tricky ones)
• first of all, we would like to cover the main topics of competitive programming — DP, graphs, basic data structures, etc.

Please note that we expect you to record and edit the video by yourself. Look at already recorded lessons to understand the expected format and structure of lessons. We have a rich history of teaching, so you can count on our advice and assistance in preparing lecture plans and problems. If video editing scares you, then here we can help.

We invite you to help grow the community and make history. I am sure that the recorded classes will be watched by tens of thousands of people (or more?).

The reward for recording one class is $1000.

If you are now red or have ever been red and you are interested in this offer, then fill out the form (open until June 28th).

Hello Codeforces!

mesanu, flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 799 (Div. 4)! It starts on Jun/14/2022 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• 5-8 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 (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth 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 fourth 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 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: Neophiliatic, Qualified, sandry24, _Anurag, jampm, TimDee, Olympia, hbarp, AlperenT, BucketPotato and VIP-tester _Vanilla_.

And thanks to NEAR for supporting this round, details can be found in this post.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

UPD: Editorial is posted!

Hello Codeforces!

On Jun/12/2022 17:35 (Moscow time) Educational Codeforces Round 130 (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 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.

Good luck to all the participants!

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

Hey, Codeforces!

We are thrilled to announce an amazing work & study opportunity with Vodafone.

Vodafone Group has partnered with Harbour.Space University to offer Bachelor's and Master’s degree scholarships in Computer Science, Data Science, Cyber Security and Front-end Development as well as MBAs and work experience in one of the leading UK telecommunication companies.

Vodafone Group is opening a new technological HUB in Malaga, an international center of excellence dedicated to research and development of technical solutions, such as Secure Networks, 5G and 6G development, Open RAN, IoT, MPN & MEC and UCC for Vodafone Business, platforms and enterprise solutions.

We are looking for various junior to mid level positions (or senior) to fill in different fields such as:

• Front-end Development
• Full-stack Development
• Backend Development
• Technical Architecture
• Enterprise Architecture

APPRENTICESHIP REQUIREMENTS

General Requirements:

• High School Diploma or Bachelor's Degree with prior work experience
• CV or LinkedIn Profile (your Codeforces rank has to be added to your CV)
• Proficiency in English (Spanish is a plus)

Requirements for Frontend Developer:

• At least 1-3 years of experience in Angular.
• At least 1-3 year of experience working in React.
• Strong knowledge of web platform fundamentals: HTML, JavaScript and CSS.
• Design and implementation of low-latency, high-availability, and performant applications
• Definition / construction of CI / CD pipelines using tools such as Jenkins, Sonar, Kiuwan.

Requirements for Full-Stack Developer:

• Minimum 3 years of proven experience in platform development (CDI/DevOps based environment). With one or more of the following:
• Java SE/ Javascript
• Scripting languages, i.e. python, perl, shell scripts.
• Proven experience in backend & frontend software systems & web applications.
• Proven experience with HTPP, MQTT, LwM2M, Kafka, various databases (SQL and non-SQL).
• Proficiency in cloud-native development.
• Hands-on experience with CDI tools.

Requirements for Java Developer:

• Industry experience with Software Platforms in Linux, on-premises and cloud
• Solid understanding of server technologies
• Strong academic knowledge and professional experience of software development: Java Enterprise, Oracle, Linux, Windows
• Good understanding of system monitoring tools and automated testing frameworks
• Experience with SQL, XML, JSON and CSV
• Experience of providing and maintaining transformations and APIs for customers and partners
• Good understanding of Databases – Oracle, MongoDB, ElasticSearch.
• Good understanding of java frameworks, SpringBoot, Spring technologies
• Good understanding of container systems (docker) and orchestrators (docker compose, Kubernetes) and messaging technologies, kafka, rabbitmq
• Good understanding of Unix shell, Perl, python to perform automation and maintenance tasks and CI/CD environments
• Educated to BSc degree level in telecommunications or related discipline with Software Development experience

Good luck on your round, and see you next time!

Harbour.Space University

UPD: Editorial is out

Hello Codeforces!

We are glad to invite you to Codeforces Round 798 (Div. 2) which will start on 10.06.2022 19:35 (Московское время). Please notice the unusual time. You will be given 5 problems and 2 hours 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 in the round.

All problems are prepared by n0sk1ll and me. We would like to thank:

• TheScrasse, nor, Riblji_Keksic, AlperenT, Sarvesh10 for testing this round and providing valuable feedback!
• gop2024 for coordinating!
• MikeMirzayanov for creating amazing Codeforces and Polygon platforms!

Thanks to NEAR for supporting this round, details can be found in this post.

We are looking forward to your participation!

Score Distribution:

$$$500-750-1250-1750-2500$$$

UPD: Editorial

Hello! Codeforces Round 797 (Div. 3) will start at Jun/07/2022 17:35 (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 ACM-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.

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 (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 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.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of our work. Problems have been created and written by ITMO University teams: MikeMirzayanov, MisterGu, myav, Gol_D, Aris, senjougaharin, me Vladosiya.

Also many thanks to Kirill22 , daubi , Fortin , Artem_Sukharev , vsinitsynav , yorky , oversolver , majorro , ilya_totl , Undying , olya.masaeva , Kniaz , Golovanov399 , farmerboy , Absyarka , Kavaliro , neeraj_joshi for testing the contest and valuable feedback.

Good luck!

UPD:Editorial

Hi Codeforces! Happy Dragon Boat Festival!

We are glad to invite you to our first Codeforces Round Codeforces Round 796 (Div. 1) and Codeforces Round 796 (Div. 2) which will be held on Jun/03/2022 17:35 (Moscow time). This round will be rated for participants of both divisions. Participants in each division will be offered 6 problems and 2 hours to solve them. The two divisions will share 3 problems.

In this round, as the best friend of the characters in Touhou Project, you are going to help them solve the problems they meet.

The problems are prepared by xiaoziyao, Yakumo_Ran, SSerxhs, Cocoly1990, LilyWhite, Elegia and me. We hope you will enjoy this round.

Great thanks to:

• 74TrAkToR for good coordination of this round and translating all statements to Russian,
• Yakumo_Ran for providing most tasks,
• SSerxhs for preparing most tasks,
• LilyWhite for polishing statements,
• Elegia, QAQAutoMaton, jqdai0815, Kevin114514, Suika_predator, loveye, Serval, ix35, Miko35, mrsrz, SanweiTreap, Eden_CY,wind_whisper,xuezhe, Cocoly1990, KaguyaH, meowcneil, plagues, marzipan, nhc, SCL_, zarubin for testing our round,
• KagamineRin, huhaoo, juju054, JohnVictor and Zcusss for other help,
• MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• NEAR for supporting this round, details can be found in this post.

Please pay attention that there will be no more than 998244353 interactive problems in this round, so learn more about interactive problems here before the contest.

Good luck & Have fun!

UPD 1:

Score Distribution:

Div2: $$$500 - 750 - 1250 - 1500 - 2000 - 3000$$$

Div1: $$$500 - 750 - 1500 - 1500 - 2000 - 3000$$$

UPD 2:

Editorial is out.

UPD 3:

Winners

Div.1:

1. Um_nik
2. Rewinding
3. jiangly
4. tourist
5. SSRS_

Div.2:

official:

1. Hanasaki
2. tkended
3. boboGM_when
4. a_nanas
5. rondoudou

unofficial:

1. Teating_
2. AgafonovArtem
3. luogubot
4. znqd3116
5. XiShui_AKIOI

Namaste Codeforces!

We are excited to invite everyone to CodeCraft-22 which will take place on 31.05.2022 17:35 (Московское время). It is rated for all people who are below yellow! (rating under 2100)

The Programming Club at IIIT-H organizes this event under Threads'22, as a part of our techno-cultural fest Felicity, IIIT Hyderabad.

There are 6 Problems with 2 hours to solve them. The scoring distribution will be released soon!

We have worked hard to keep the statements clean and the pretests strong! After the contest, step-wise tutorial and video tutorial will be released along with the code!

• This round was wonderfully co-ordinated by darkkcyan and KAN orz!
• This round was a joint effort by rahulgoel, menavlikar.rutvij, ltc.groverkss, akcube, fangahawk, JadeReaper, keyurchd_11 and me!
• KAN also translated the statements to Russian! благодарю вас
• We would like to thank our army of testers for providing valuable feedback: generic_placeholder_name, Lomk, TheScrasse, vinfat, codelegend, BucketPotato, ajit, manish.17, Dragonado, anmolagarwal999, Lihwy, kryptai, ak2006 and brj!
• Thanks to nandini.maroo and akcube for helping with the poster design.
• And finally, we would thank MikeMirzayanov for the platforms Codeforces and Polygon without which all this would not be possible.

We hope you enjoy this contest!

UPDATES

Score Distribution: 500 — 750 — 1250 — 1750 — 2250 — 2750
Editorial is out.

Winners

Congratulations to all the winners for such an amazing performance.
Global Top 5
1. tourist
2. ksun48
3. noimi
4. jiangly
5. Um_nik

Official Top 5
1. JrNTR
2. YinJinRun
3. Remakee
4. see_wo
5. HowtobeRed

We will send a CF personal message to the winners of the T-shirts soon.

PRIZES

The following twenty lucky participants receive a T-shirt:

• Top 10 Indian participants.
• Random 10 from top 100 (ranks 11-100) Indian participants.

These ranks are determined from the combined unofficial rank list. People who have their Country set to India in their CF profile will qualify as Indian participants.

We are giving T-shirts to Indian participants only to avoid logistic issues that we have to face during international delivery. We apologize for this limitation, we will try our best to bring international prizes too from next year.

Thanks to NEAR for supporting this round, details can be found in this post.

We will hold Codeforces Round 794 (Div. 1) and Codeforces Round 794 (Div. 2).

• Contest URLs: https://codeforces.net/contest/1685, https://codeforces.net/contest/1686
• Unusual start time: 25.05.2022 20:35 (Московское время)
• Duration: 135 minutes
• Number of Tasks: 6 for Div2, 5 for Div1
• Rated range: $$$(-\infty, 1899]$$$ for Div2, $$$[1900, \infty)$$$ for Div1
• Writer: antontrygubO_o
• Testers: golions, oleh1421, Geothermal, nor, TheScrasse, timreizin, emorgan, Um_nik, 244mhq, Kuroni, ak2006
• VIP-tester: errorgorn
• Coordinator and author of one problem without which round would be unbalanced: dario2994
• Creator of the amazing Codeforces and Polygon platforms: MikeMirzayanov

The point values will be:

Div2: 500 — 1000 — 1500 — 2000 — 2500 — 2500

Div1: 500 — 1000 — 1500 — (1500 + 1500) — 3500

We are looking forward to your participation!

UPD 1: Thanks to NEAR for supporting this round, details can be found in this post.

UPD 2: Editorial

UPD 3: Congratulations to winners!

Div1:

1. Rewinding

2. jiangly

3. ecnerwala

4. gamegame

5. maroonrk

Div2:

1. lmqzzz

2. Teating_

3. lunchbox

4. Nida1097

5. demacia

Hello Codeforces!

On May/23/2022 17:35 (Moscow time) Educational Codeforces Round 129 (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 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.

Good luck to all the participants!

UPD: Editorial is out

Hi Codeforces!

I am pleased to invite you to Codeforces Round #793 (Div. 2), which will take place on May/22/2022 17:35 (Moscow time). You will be given 6 problems and 2 hours 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 in the round.

All problems in this round were prepared by me and rivalq. We have worked on this round for a long time and hope you find every problem interesting.

I would like to thank:

• antontrygubO_o for marvellous coordination of the round.
• errorgorn, kclee2172, AmShZ, nvmdava, TheScrasse, aryanc403, koderkushy, PurpleCrayon, nor, AlperenT, towrist, ExplodingFreeze, conquered, naresh0839, The_Hawkeye, Siuuuuu_7, GuptaSir, sp005, obliviousz, davidgarg20, ak2006, and the_hyp0cr1t3 for testing this round and giving really valuable feedback.
• MikeMirzayanov for the amazing Codeforces and Polygon platforms!
• You for participating and upvoting.
• NEAR for supporting this round, details can be found in this post.

Score Distribution:

750 – 1000 – 1500 – 2000 – 2500 – 2750

Good luck and have fun! See you in the standings. Make sure to read the statements very carefully.

Thanks to ak2006, video editorials for some of the problems will be available on his channel after the round.

Congratulations to winners!!

Global Top 5:

1. jiangly, superfast AK!

2. Beduardo

3. SSRS_

4. neal

5. turmax

Official Top 5:

1. Beduardo

2. Brewess

3. Kizuna_AI

4. Focalors

5. csyakuoi

Special mention to AwakeAnay for the only Indian to AK the round!

UPD 1: Links to video editorials of Problem B and Problem C

UPD 2: Editorial for problems A-D is here.

UPD 3: Editorial for E is added.

UPD 4: Editorial for F is added.