Moo! (Hello Codeforces!)

I’m very excited to invite you to Codeforces Round 621 (Div. 1 + Div. 2), which will take place on Feb/17/2020 18:35 (Moscow time).

In this round, you will be helping Farmer John and his prized cow Bessie cowmplete some fun tasks.

The contest will have 7 problems and is combined and rated for both divisions. The duration is 2 hours and 15 minutes. The problems are prepared by me (FieryPhoenix) and dragonslayerintraining. We tried very hard to make them interesting and hope that you will enjoy them too!

This round would not have been possible without the wonderful coordination by adedalic and cdkrot. Thank you so much to the testers as well for all the invaluable advice: tmwilliamlin168, walnutwaldo20, nikolapesic2802, bfs.07, Rods, lynmisakura, JustasLe, and hocky. As always, thanks to MikeMirzayanov for the best systems Codeforces and Polygon.

Good luck and more importantly, have fun and learn something new!

UPD: The scoring distribution is 500 — 1000 — 1500 — 2000 — 2500 — 3000 — 3500

UPD: Editorial

UPD: Thank you for participating! Huge congratulations to the winners!

1. jqdai0815

2. 300iq

3. ohweonfire

4. yosupo

5. ksun48

안녕하세요, 코드포스! (Hello, Codeforces!)

I'm glad to invite you to Codeforces Round 620 (Div. 2). The contest will start at Feb/15/2020 16:05 (Moscow time), and it is rated for all participants with ratings under 2100.

You will be given 6 problems and one of the problems has 2 subtasks. The contest duration is 2 hours. The score distribution will be announced later.

All problems are prepared by me, with huge help from the testers with developing great solutions.

I'll be on the community Discord server after the contest to share my thoughts and get feedback about the problems.

Thanks to 79brue, molamola., Savior-of-Cross, evenharder, cs71107, Justice_Hui, rkm0959, chpark1111, imeimi, InfiniteChallenge, gaelim, jh05013 (Good tester), yuto0518, N_jara, aryanc403, SnowGoose, solvemproblr, surung9898, and ko_osaga for testing the round. I would also like to thank 300iq for round coordination, and MikeMirzayanov for the great Codeforces and Polygon system.

Hope you enjoy the problems!

UPD: The scoring distribution is 500 — 1000 — 1500 — 1750 — 2000 — (2000 + 1000)

UPD2: The contest is finished! Thanks so much for your participation! The editorial is here.

UPD3: Congratulations to the winners!

Div. 2

1: Itst_boyfriend

2: COVID-19

3: naive_xay

4: anta.baka

5: ChitandaEru

Unofficial Div. 1

1: wucstdio

2: ksun48

3: jiangly

4: uwi

5: teapotd

From 28.01.20 to 07.02.20, Petrozavodsk State University held 38th Petrozavodsk Programming Camp. 47 teams participated in the competition from 33 universities, 25 cities, 11 countries (Russia, Belarus, Kazakhstan, Poland, Romania, Latvia, Ukraine, South Korea, China, USA, Japan)

Petrozavodsk Programming Camp is traditionally a training platform for International Collegiate Programming Contest (ICPC) winning teams: over the past 18 years, 13 times the camp participants became winners in ICPC World Finals. This time from 47 of participating teams 18 teams will take part in ICPC World Finals 2020.

Petrozavodsk Programming Camp consists of nine days of contests and two upsolving days days off between them. One of the camp's features is that participants and sponsors are generally the authors of contests. This time the authors were: 300iq; tourist; jqdai0815; teams from the following universities: SPb SU, Lviv National University, Jagiellonian University, Nizhny Novgorod SU; as well as Yandex team.

The participants enjoyed karting, bowling, and also attended events from partners of the competition: AIM Tech provided beer and snacks to members of AIM Tech Poorly Prepared Contest, Yandex puzzled participants with questions on the Yandex.Quiz, Botan Investments talked about Cyprus AI investor trip, and Huawei gave a lecture about Big Data Algorithms.

Hello everyone!

Will you be single and bored during Valentine's Day? Never fear, as zscoder is here to cure your boredom.

I would like to invite you to Valentine's Day Contest 2020, which will take place on Friday, February 14, 2020 at 12:30 GMT. The contest is unofficial and unrated, but the quality of most (if not all) of the problems are comparable to problems from a Codeforces round. I am the author of all problems.

The contest format will be IOI format, which means that each problem is worth $$$100$$$ points, and there are subtasks for each problem. There will be no time penalty. The problems are not sorted in increasing order of difficulty. Unlike IOI, you are allowed to use any templates or notes you have.

There are 7 problems to be solved in 3.5 hours. There is an interactive problem, so feel free to learn about them here.

There will be a special shoutout to the first person to AC for each problem (and also the first person to get all 7 ACs >_<).

The difficulty of the contest is aimed at higher-rated Div. 2 (Expert) to mid-red (low International Grandmaster) level participants but everyone is welcome to join the contest. Of course, if you are not single and are still free to join the contest, you are welcome to join as well. XD

Thanks to the testers Kuroni, tmwilliamlin168, duckmoon99, gamegame, ToxicPie9, dorijanlendvaj, kostia244 and alimq for testing the problems and MikeMirzayanov for the wonderful Codeforces and Polygon systems that made this contest possible.

The contest will be held (tentatively) within a Codeforces group and the link will be posted later.

UPD: The contest will be held as a training contest on Gym. (which will appear later) The contest is now available on Gym. Registration opens $$$6$$$ hours before contest starts.

If you are a coach in Gym, remember to disable coach mode before joining the contest. ^_^

I will be on the AC Discord server to discuss the contest after it ends.

Hope to see you in the contest!

UPD 2: Contest is over! Thanks to everyone who participated and made this Valentine's Day less lonely for me. Congratulations to the top 10:

Rank 1: Radewoosh (with 577 points)

Rank 2: jiangly and 244mhq (tied with 500 points)

Rank 4: NoLongerRed (with 426 points)

Rank 5: sigma425 (with 409 points)

Rank 6: noneTP (with 351 points)

Rank 7: wygzgyw (with 345 points)

Rank 8: chocorusk (with 340 points)

Rank 9: BigBag (with 334 points)

Rank 10: waynetuinfor (with 326 points)

Also, here is a shoutout to all the "first to AC"s:

Problem A: sigma425 at 00:16

Problem B: Unsolved during contest time :(

Problem C: 244mhq at 00:25

Problem D: TLE at 00:44

Problem E: TLE at 02:38 (and only AC for E during contest!)

Problem F: Moniphant at 00:12

Problem G: shirakami.rin at 00:24

UPD 3: The editorial is here!

Hello Codeforces.

I would like to invite you to participate in Codeforces Round 619 (Div. 2) which will take place on Feb/13/2020 17:35 (Moscow time).

The contest will be rated for Div. 2 participants. It will include 6 problems, and you have 2 hours to solve them. The problems were created and prepared by me.

I would like to thank KAN, isaf27 for coordinating this round. And 300iq, -is-this-fft-, AdvancerMan, Dup4, Agnimandur, Tzak, DomiKo, Aleks5d, Supermagzzz, manta1130 for testing the round. I also would like to thank MikeMirzayanov for great and perfect Codeforces and Polygon systems.

hope you enjoy the contest and find some interesting problems.

UPD: Score distribution: 500-1000-1250-1750-2500-2500.

The round has ended. Thanks for participating and congratulations to the winners.

Div1:

1. jqdai0815
2. dreamoon_love_AA
3. LayCurse
4. wucstdio
5. neal

Div2:

1. COVID-19
2. MofK_from_Bangladesh
3. jxdxhy
4. Crazy_Diamond
5. DovydasVad

Tutorial

Hello Codeforces!

On Feb/12/2020 17:35 (Moscow time) Educational Codeforces Round 82 (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 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.

Good luck to all the participants!

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

Hi Codeforces!

This is not the last call for participation, but we’re almost there. We have extended the early bird discount deadline of Hello Muscat ICPC Programming Bootcamp until this Sunday, February 16th. Remember you can request a support letter to present to your university, employer or local companies to sponsor your participation and trip to the bootcamp.

We would also like to remind you that if your team is going to the ICPC World Finals in Moscow this June, you can fill out the form below to see if you are eligible for a full scholarship for our Bootcamp (flights not included), and we will contact you within three days to let you know about the results.

UPD: There will be 7 problems in the round

Congratulations to the winners:

39 successful hacks and 147 unsuccessful hacks were made in total!

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

UPD: Editorial is out

Hello Codeforces!

We are glad to invite you to the upcoming Codeforces Round #618, which will start at Feb/09/2020 17:05 (Moscow time).

Each division will consist of 5 problems and will have 2 hours to solve the problems. There will be an interactive problem in the round. Learn more about them here.

This round was prepared by rotavirus, rotavirus, rotavirus, rotavirus, antontrygubO_o and nvmdava. We would like to thank MetB, stefdasca, cfalas, gamegame, hugopm, Redux, dorijanlendvaj, imbr92, CP_Sucks, 300iq, Rahul, AryaKnight, 244mhq, manish.17, Um_nik, mblazev, pseudocoder10, aryanc403, box for testing and their invaluable feedbacks. And special thanks to MikeMirzayanov for making this round possible and antontrygubO_o for coordination of the round.

We hope that you will enjoy the problems we've set, and wish you good luck and a high rating.

Upd 1. Some of us might be online at AC discord server after the round ends.

Upd 2. Score distribution:

• Div2: 500 750 1250 1750 2000
• Div1: 500 1000 1250 1750 2250

The contest is over. Congratulations to the winners.

Div1:
1. jqdai0815
2. TLE
3. Radewoosh
4. zhouyuyang
5. Benq

Div2:
1. ntftxdy
2. qsmcgogo
3. ZhouShang0817
4. sarthakmanna
5. nantfaker

Editorial

Hi Codeforces!

The platform recently turned 10 years old. We accept your congratulations at https://mirror.codeforces.com/10years. Please review the progress in 2019 and support the anniversary crowdfunding campaign. Your donation will be a contribution to the future of Codeforces, will help its development and work. We need resources to continue to host rounds, not to stop developing, to innovate and to maintain the existing infrastructure.

In 2019, together with numerous writers the coordinators worked on problems: KAN, 300iq, cdkrot, arsijo and recently joined isaf27. And this year, rounds coordinated by other experienced members of our community can be expected. Intrigued?

The main innovations in the platform are implemented by me and the developers: kuviman, cannor147 and geranazavr555. Una_Shem provided great organizational assistance. Thanks!

I send special rays of gratitude to problem writers and testers! This year we have had more rounds than ever before!

Time to take stock of 2019.

Partner Events

We are pleased to hold programming competitions with companies or for companies. I'm sure this is a great way to support the community of young programmers and hire talented candidates. Here is a list of our main partners this year:

• Telegram and personally Pavel Durov is supporting Codeforces activities for many years, every regular round is held with their help, thank you!
• Mail.Ru — Technocup and Russian AI Cup
• VK, VK Cup — now a personal multi-track competition for Russian-speaking programmers
• XTX Markets, Codeforces Global Rounds — a series of 6 rounds with a separate scoring and souvenirs for the best participants
• Harbour.Space University — a series of educational rounds, the selection of summer school Tech Scouts
• JetBrains, Kotlin Heroes Rounds — Kotlin programming language contests
• Huawei — research competition (marathon) with elements of machine learning
• Forethought, Forethought Future Cup — a two-level competition with the Final at Forethought headquarters (San Francisco) and the mirror contest for worldwide participants
• Dasha.AI, Dasha Code Championship — a two-level competition with the Final at St. Peterburg and Novosibirsk (and the mirror contest for worldwide participants)
• VeeRoute — research competition (marathon)
• Microsoft, Microsoft Q # Coding Contest — unusual quantum computing competition

Hi Codeforces!

Colleagues from Google asked to share the announcement. Join, it'll be fun!

Hello!

Google’s team programming competition Hash Code is back for another year of challenging developers around the world to solve a Google engineering problem. Think you could optimize the layout of a Google Data Center? Or how about perfecting video streaming on YouTube?

If you’re up for the challenge, sign up to compete by February 17 at g.co/hashcode.

Hash Code takes place over 2 rounds:

• an Online Qualification Round: Thursday, February 20 from 17:30 — 21:30 UTC: Compete from this virtual round wherever you’d like, including from a Hash Code hub. Hubs allow for teams from the same community (e.g. university or coding club) to compete side-by-side in a fun and exciting environment.

• a Final Round at Google Ireland: Saturday, April 25: Top scoring teams from the Online Qualification Round are invited to our Dublin office to vie for cash prizes and the title of Hash Code 2020 champion.

Whether you’ve just started coding or you’ve been participating in programming contests for years, Hash Code is a great chance to flex your coding muscles, get a glimpse into software engineering at Google, and have some fun. Take a look at previous Hash Code problem statements to see the engineering challenges participants have tackled in the past.

Register by Feb 17 at g.co/hashcode

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Hello! Codeforces Round 617 (Div. 3) will start at Feb/04/2020 17:35 (Moscow time). You will be offered 6 or 7 problems (or 8) 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 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 or 7 (or 8) 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 a 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.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Daria nooinenoojno Stepanova, Mikhail awoo Piklyaev, Maksim Neon Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

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UPD: Editorial is published!