Hello Codeforces!

On Dec/27/2019 17:40 (Moscow time) Educational Codeforces Round 79 (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 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.

Good luck to all the participants!

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

Hi Codeforces!

Last spots available for Mike Mirzayanov's course Advanced Algorithms and Data Structures, which will take place in Barcelona, from the 6th to 24th of January, 2020.

The course will consist of three weeks of training, 5 training days each week. The program includes daily lectures and practical exercises. It will be quite educational, insightful and entertaining!

Remember, there’s a special price of 1,000 EUR* for all Codeforces users.

* The cost does not include travel or accommodation.

If you’re interested, send us a message at hello@harbour.space and we will guide you through the next steps.

UPD: Editorial is out

Do you already have a New Year's mood?

And we have traditional gifts!

Change Handle Feature

Hurry! Only until the 10th of January, you can change your handle (but only once)! Note that it will be possible to roll back the changes or change the handle again only after a year. Be careful what you wish for.

You can change your handle to the new one which wasn't used before by anybody or which was used by you before. The links to a profile page with an old handle would automatically redirect to the actual profile.

Again, this year if you took part in at least 10 rounds you can request a handle of an inactive participant. It means that the participant should have a period of activity on Codeforces of at most 180 days, this period should be in 2016 or earlier. The inactive participant can't have posted comments, messages and so on. It can't take part in more than 2 contests. It will be automatically renamed and informed by email. A user has the opportunity to request back his/her handle: in this case, we will roll back the change and return your previous handle to you. If you can't change your handle to another, it means that some requirement doesn't meet. Please do not ask me to do something with it. I'm not Santa Claus.

Talking about handles I always
reminisce the following story. Once a user wrote me the message: "Please change my handle from I_love_Valya to I_love_Sveta, as I no longer love Valya ..."

New Year's Masquerade of Colors and Ranks

The traditional magical tab has appeared in the profile setting. Happy New Year!

Hello, Codeforces!

HSE Faculty of Computer Science and Yandex launch registration for the 3rd International Data Analysis Olympiad (IDAO 2020). The platinum partner of IDAO 2020 is Qiwi.The Olympiad includes two stages:

Online Stage (Jan 15 – Feb 11, 2020):

• Track 1: Traditional machine learning competition on Yandex.Contest platform. You will need to make new predictions and upload them to the automatic verification system.

• Track 2: Come up with a solution for the same problem, keeping within a rigid framework of time and memory used.

Final (April 2-5, 2020):

• top 30 teams according to the Online Stage results will be invited to the on-site final, which will be held on April 2-5 in Yandex office, Moscow.

• In the final 36 hours of the competition, participants will try not just to train the model, but to create a full-fledged prototype, which will be tested both in terms of accuracy and performance.

As part of IDAO Final, performances and master classes of world experts in machine learning and data analysis are also planned. Winners and prize-winners of IDAO 2020 will receive valuable prizes and gifts, as well as an advantage in entering Yandex School of Data Analysis and master's programmes at the HSE Faculty of Computer Science.

In 2019, 2187 participants from 78 countries took part in IDAO, and 79 participants from 7 countries met in the final in Moscow.

Learn more: https://idao.world/

Hello Codeforces!

We're glad to invite you to Codeforces Round #610 (Div. 2), which will be held on Dec/24/2019 17:35 (Moscow time). It will be rated for all participants with a rating below 2100. You will be given six problems and two hours to solve them.

The problems were invented and prepared by the team from ITMO University: Supermagzzz, Stepavly, AdvancerMan, unreal.eugene, MikeMirzayanov.

Special thanks to MikeMirzayanov for great systems Codeforces and Polygon and coordinating round preparation.

UPD1: Special thanks to the ITMO University testers team: budalnik, Alexxx, Darui99, golikovnik, sharepoLOVEDDD, Mr.Hakimov, zergey.gad, MeowMr, Ilya-bar, 1ncendiary

There is an interactive problem in the round. You can read the guide for interactive problems here.

UPD2: Scoring: 500 — (500 — 1000) — 1750 — 2500 — 2500

We hope you will enjoy the problems. Good luck, wish you a high rating!

UPD3: Congratulations to the winners!

1. Tsypkokokokoko
2. K.Yuuki
3. hyhtsdy
4. ptica
5. junukwon
6. gumnam
7. AnotherRound
8. conqueror_of_obd
9. rtilikay
10. p1rattttt

Editorial will be published soon.

UPD4: Editorial is out!

Hello, Codeforces community!

I'm glad to invite you to Codeforces Round #609 (Div. 1) and Codeforces Round #609 (Div. 2), which will be held on Dec/21/2019 14:05 (Moscow time). The round will be rated for both divisions.

The problems were taken (mostly) from the ByteDance — Moscow Workshops Online Contest, that's happening at the same time. They were prepared by myself and tested by jqdai0815, Claris, quailty, jiry_2 (camp TA team), and gamegame, isaf27, tmwilliamlin168, mango_lassi, WNG, Lewin, sas4eka, UselessDev, Aleks5d,MrDindows.

ByteDance is a technology company operating a range of content platforms that inform, educate, entertain and inspire people across languages, cultures, and geographies. ByteDance has partnered with Moscow Workshops ICPC 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 10th to 16th, 2020.

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 https://programcamp.bytedance.com/.

UPD: Editorial

Hello Codeforces!

On Dec/19/2019 17:35 (Moscow time) Educational Codeforces Round 78 (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 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.

Good luck to all the participants!

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

Hi Codeforces!

The deadline to apply for our Master’s Scholarship in Bangkok is very soon!

Don't miss your chance and apply for our progressive Master’s programs in Data Science and Cyber Security in just 3 steps:

1. Submit your CV to see if you are an eligible candidate for the scholarship
2. If your profile matches the requirements, one of our admissions officers will get in touch with you
3. Apply for the program, pay the 125€ application fee, pass a series of interviews, and if you’re accepted, pack your bags to Bangkok!

And if you know someone who might be interested in Digital Marketing, High Tech Entrepreneurship, Interaction Design or FinTech, send them our way!

Also, don’t forget to read our newest blogs!

• 4 Types Of Data Biases (And How To Avoid Them)

• Creating Your Dream Job Has Never Been Easier

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD: Editorial is out

In 2019, with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds were held. Each round was common for both divisions and had 7–9 problems. The duration of the rounds was 2-3 hours, depending on the number and complexity of the problems. 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 authors and problem testers as well.

The prizes for the 6-round series in 2019:

• 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:

Hi!

Are you tired after a weekend of three (3) contests? Or are you ready for another one? On Dec/17/2019 18:05 (Moscow time) we will host Codeforces Global Round 6!

It is the sixth round of a new series of Codeforces Global Rounds supported by XTX Markets. The rounds are open for everybody, the rating will be updated for everybody.

You will be given 8 problems and 150 minutes to solve them. The scoring distribution will be 500-750-1250-1750-2000-2500-3500-4000.

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2019 (current results):

• 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 the whole series get sweatshirts and place certificates.

The problems of this round were developed by me. I will be available on Discord to discuss the problems after the contest.

I would like to thank:

• XTX for supporting this series of rounds,
• BledDest and isaf27 for their help in the round's coordination,
• darnley, dacin21, craborac, nk.karpov, Roms, defolaut for testing the round (more testers are coming),
• MikeMirzayanov for Codeforces and Polygon.

UPDATE: The round is over! I hope you enjoyed it despite the second half being more difficult than anticipated. The system test will begin shortly.

UPDATE 2: Editorial

UPDATE 3: Congratulations to winners:

1. webmaster
2. sunset
3. tourist
4. whzzt
5. hos.lyric
6. eatmore

UPDATE 4: Global Rounds 2019 final results

Hello Codeforces!

Codeforces Round 608 (Div. 2) will be held on Dec/15/2019 12:15 (Moscow time). The round will be rated for Div. 2 contestants. There will be 6 problems for 2 hours. Please, notice that the start time is unusual.

The round will be rated for the participants with rating lower than 2100. The statements will be available in Russian and English.

The round coincides with (and is based on) a local Saratov's olympiad for high school students. That's why we ask the participants of the olympiad to stay silent and don't share the statements of the contest with anyone. Unfortunately, we cannot add all the problems to the round, it will contain only six problems.

The problems were proposed and prepared by Alexander fcspartakm Frolov, Adilbek adedalic Dalabaev, Vladimir vovuh Petrov and me.

We also would like to express our gratitude to Mike MikeMirzayanov Mirzayanov for the permission to make a mirror and Codeforces and Polygon platforms, to our coordinator Dmitry cdkrot Sayutin or his help with testing the problems and preparing the round, and to the team of testers: MrPaul_TUser, Stresshoover, Supermagzzz, artsin666, defolaut, Peinot, PrianishnikovaRina, nuipojaluista, Ivan19981305, lankin.i, Pavlova, Decibit, dmitrii.krasnihin, AlexSap, unreal.eugene.

Scoring distribution: 500 — 1000 — 1250 — 1750 — 2250 — 3000.

Good luck!