UPDATE: the editorial is here

Link to the online mirror

Hello CodeForces! This year again, I'd like to invite you to the online mirror of an open championship of Switzerland called HC2 (the Helvetic Coding Contest). A mirror was also held one, two and three years ago.

The Helvetic Coding Contest is a yearly contest held at the EPFL in Lausanne by the PolyProg association. The contest itself took place on April the 13th, but the online mirror is scheduled on Sunday, 7th of July, 10:05 Moscow time. The duration is 4:30.

Rules:

• you can participate in teams or individually (1-3 people),

• standard ACM-ICPC rules (no hacking),

• the contest is not rated,

• if you have participated in the onsite contest, please do not participate in the mirror.

The contest this year is Doctor Who-themed. It features 5 series of 2-3 related tasks with increasing difficulty (easy/medium/hard). (For the online mirror, we will skip one series that had appeared in the onsite contest.) Sometimes it may be the case that a solution for the hard version solves all of them, but usually not. We think that the problemset is diverse and interesting, and while the contest is ACM-style, you will find that some problems are not so standard. Most easy&medium problems are even solvable in Python, so you can also recommend this contest to your newbie friends :) We promise to post a nice editorial as soon as the contest ends.

Acknowledgments: the problems were set by bgamlath, DamianS, esrever, milenkoviclazar, Wajeb (who coordinated), and myself. Thanks also go out to people who helped with the statements and testing: anayMehrotra, Michalina Pacholska (who also draws the cows), cdkrot for the Russian statements, KAN for CodeForces coordination, as well as everyone involved in the actual onsite contest, who are too many to name here. We also thank the sponsors Open Systems and nexthink. Lastly, thanks to MikeMirzayanov for CodeForces and Polygon (which was used to prepare the problems).

Finally, in a bit of autopromotion, note that you can use Hightail to automatically test your solutions :) Good luck!

After-contest UPDATE:

>>> Editorial <<<

Also:

• two extra problems from the onsite contest that were left out for the online mirror are available in the Gym

• the new uphacking feature is available for all problems except A3 and C3

Thanks to everyone who participated! We hope you have enjoyed the problems. The top three teams are:

1. 大象大象你的鼻子为什么那么长 (solved all 14 problems!): FizzyDavid, 300iq, TLE

2. zxtxdy (13 problems): cuizhuyefei, MarkF, zx2003

3. helveticow (12 problems): scott_wu, ksun48, ecnerwala

See you again next year!

Hi Codeforces.

Recently there have been several improvements on the website. A little later, I will write a short note about them. Here I want to tell about a noticeable new functionality that has recently been implemented by kuviman.

Sometimes after the end of a round there are requests in comments to add a particular test. And problem writers or coordinators add it manually. Now this process is automated.

Meet the uphacking phase!

Now, after the end of almost any contest, participants from Div.1 have the opportunity to hack any solution in this contest during the week. Yes, including official solutions from rounds. In case of successful hacking:

• Your test will be automatically added to the problem and will be used in the future when testing new solutions for this problem;
• If a hacked solution is a practice (i.e. upsolving), then its verdict will change to “hacked” otherwise its verdict will remain unchanged;
• The participant whose solution has been hacked will be notified via system private message;
• Each solution can be successfully hacked only once.

In order to add only adequate and reasonable tests, it is forbidden to hack solutions that intentionally contain a mistake. Please strictly follow this rule. It is because of the possibility of inadequate behavior that we cannot open uphacking for everyone.

I hope that this innovation will be useful and tests for problems will become even better!

• MikeMirzayanov

UPD: Probably, later we will extend uphacking phase and reduce the rating bound.

Hello, Codeforces!

We are glad to invite you to the Codeforces Round #572, which will be held on Friday, 5 July at 18:05. The round will be rated for both divisions (as this time we thanked MikeMirzayanov).

Round was prepared by us, antontrygubO_o and 244mhq. This is our first round, and, as we hope, not the last one!

A lot of thanks to arsijo for the excellent coordination of the round, gepardo, Mediocrity, kefaa, zoomswk, ecnerwala, AllCatsAreBeautiful, gop2024, Markellonchik, dasfex, taran_1407, ankeet, DenisPushkin, austrian_artist, mmello, sas4eka for the testing and valuable comments, and to Mike MikeMirzayanov Mirzayanov for the amazing platforms Codeforces и Polygon. (please rated)

Participants in each division will be offered 6 problems and 2 hours to solve them. We strongly recommend reading statements of all problems! The scoring distribution will hopefully be announced before the round begins.

We wish you good luck and high rating!

UPD1: Shortly after the contest, we'll be on the community Discord server to discuss the tasks.

UPD2: Slight corrections: participants in Div $$$1$$$ will be offered $$$5$$$ problems, one of which will have $$$2$$$ subtasks, while participants in Div $$$2$$$ will be offered $$$6$$$ problems, one of which will have $$$2$$$ subtasks. Please note that subtasks will be unusual this time and will differ not only by constraints.

UPD3:

Scoring distribution of Div $$$2$$$ round: 500 — 1000 — 1250 — (500 + 1250) — 2250 — 2750

Scoring distribution of Div $$$1$$$ round: (250 + 750) — 1250 — 1750 — 2250 — 2500

UPD4: Editorial

UPD5 Congrats to winners!

Div 1:

1. Um_nik

2. ugly2333

3. Radewoosh

4. Marcin_smu

5. Endagorion

Div 2:

1. CSWhisky

2. handsomeIvan

3. philologist

4. teamskiy

5. NeoGul

Hello Codeforces!

On Jun/30/2019 17:45 (Moscow time) Educational Codeforces Round 67 (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 participants!

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD: Editorial is out

Hello,

Do you remember my post New: Diagnostics of Solutions in C++? If not, please read it.

Recently, I've implemented better UI to show you diagnostics. Now in on the status pages sometimes you can notice something like this:

Click to the and you'll see the code with the highlighted problematic line and description with the possible reason of the mistake.

Do you like it?

Hi everyone!

The rated Codeforces Round #571 (Div. 2) will take place on Jun/28/2019 11:20 (Moscow time). This round is based on the Kremenchuk Summer Programming Cup 2019.

The contest is prepared by Dalgerok, Karasick, stanislav.bezkorovainyi, antontrygubO_o, danya.smelskiy, and me.

You will have 2 hours and 15 minutes to solve 6 problems.

Good luck!

We apologize for the issue that happened with the problem B. The round is unrated. If you want to read my emotional reply about it, please read this.

<almost-copy-pasted-part>

Hello! Codeforces Round 570 (Div. 3) will start at Jun/26/2019 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 Mikhail awoo Piklyaev, Maksim Neon Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</almost-copy-pasted-part>

UPD: I also would like to thank Ashishgup and kocko for help with round preparation and testing!

UPD2: The contest will be extended for 15 minutes because the problems are more interesting than we thought. We also advise to read all the problems because some of them may have the same difficulty and we cannot know which one will be easier for you than the other.

UPD3: Editorial is published!

UPD4:

Congratulations to the winners:

Congratulations to the best hackers:

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

We are happy to announce that Moscow Workshops ICPC opens remote participation for division A in the Discover Vladivostok 2019 Programming Workshop.

Participants will receive a single login for a team of one, two or three people and will be able to choose a convenient time for solving problems. Participants of both full-time and distance training programs will do the final contest simultaneously. Analysis of all problems will also be available for remote participation students.

Among the trainers will be Filipp DPR-pavlin Rukhovich, co-coach of the bronze medalist MIPT team at the ICPC World Finals 2019; former ICPC finalist, present Head of Programming Committee in Grodno and Vladivostok's Workshops and in the Open Moscow Trainings; Ilya izban Zban, ICPC 2017 World Champion!

Remote participation is a unique opportunity to join the world of competitive programming when one could not manage to travel far.

While registering, please make a note in the note field that you would like to participate remotely. Here is the registration link

Remember that citizens of 18 countries have prerogative to get a free E-visa for 8 days to Vladivostok. Search here for the details

Hi, Codeforces!

We are glad to invite you to take part in Codeforces Round 569 (Div. 1) and Codeforces Round 569 (Div. 2), which will be held on Friday, June 21, 2019, at 19:35. The round will be rated for all participants from both divisions.

Problems for the round have been proposed by Ivan ScreaMood Fedorov, Kyrill kirillbogatiy Bessonov, Mukhammadjon Mr.Hakimov Hakimov, Fedor ---------- Ushakov, Fedor Kuyan Kuyanov, and me, Dmitry gop2024 Grigoryev.

The round have been prepared by us, Dmitry gop2024 Grigoryev, Fedor ---------- Ushakov, Dmitry TheWayISteppedOutTheCar Piskalov and Mukhammadjon Mr.Hakimov Hakimov.

We'd like to give thanks to Ildar 300iq Gainullin for excellent coordination of the round, to Sooke Sulfox Gnar, Xiuhan sunset Wang, Ziqian TLE Zhong, Junzhao FizzyDavid Yang, Jiaxuan samjia2000 Gao for testing and to Mike MikeMirzayanov Mirzayanov as well for his unbelievable Codeforces and Polygon platforms!

Participants in each division will be offered 5 problems and 2 hours to solve them. During the round, you will be helping pupils of one usual Moscow school. Score distribution will be announced, traditionally, closer to the start of the contest

Good luck!

UPD Score distribution for Div.2 is standart — 500-1000-1500-2000-2500

Score distribution for Div.1 — 500-1000-1500-1750-2250

UPD2

Thank you for your participation in the contest!

List of the winners of the contest:

Div.2

1. PSMaoTheKingOfAzerbaijan

2. atacan

3. Shayan.Kashefi_A

4. LiPro

5. BrutBurger

Div.1

1. Radewoosh

2. ACRush

3. ecnerwala

4. mango_lassi

5. neal

My frank congratulations to all the winners!

The editorial