Hello, Codeforces!

Educational Codeforces Round 15 will take place on 29 July 2016 at 18:00 MSK for the first and the second divisions.

The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.

We with Mike MikeMirzayanov Mirzayanov decided to prepare this Round, because Edvard Edvard Davtyan is very busy at his new job. Good luck and have fun!

UPD Competition completed! Thank you all! Editorial

UPD2: Tomorrow (July 31st, Sunday) at UTC 10:00 there will be an online mirror of Yandex.Algorithm final round.

Enter contest.

Everybody are invited to participate! You may discuss problems in comments after the contest ends.

UPD3: The online mirror has finished! Congratulations to ImBarD aka Vercingetorix for taking the first place.

Problem editorial

===================================================

Hi everybody!

We're glad to remind you that tomorrow, July 29th, at 9:00 AM UTC there will be the Final Round of Yandex.Algorithm 2016 in Minsk. List of finalists and elimination stage results are available on Yandex.Algorithm website.

You can watch follow the news on final round at Yandex.Algorithm website. Want to solve final round problems? On Sunday, July 31st, at 10:00 AM UTC there will be a mirror of the competition. Everybody can participate in it, solve the same problems as finalists and try his or her best on the finals' problemset.

The final round has been prepared by authors of previous stages of Yandex.Algorithm: Endagorion, Romka, Chmel_Tolstiy, GlebsHP, snarknews, Gassa and your humble servant. We believe that problems are various and interesting.

In this post after the cut I'll write some comments about what happens in the contest trying not to spoil any important details (we don't want to provde help or to ruin contest for any of the participants, isn't it?).

See you tomorrow!

UPD:

Congratulations to the winners!

1. Egor winning 300 thousands of rubles.
2. W4yneb0t winning 150 thousands of rubles.
3. rng_58 winning 90 thousands of rubles.

Final results are available here. The competition is finished, everybody are invited to participate an online mirror on Sunday!

Hello everybody!

Today the second regular rated round based on problems of VK Cup 2016 Final Round will take place. Of course, we have created some more easy problems to fulfill the requirements of different skill levels and make the contest interesting for everyone.

The commentators of the previous announcement pointed out that I forgot to thank MikeMirzayanov for making Codeforces and Polygon so awesome. I was wrong, Mike, that's really cool :)

Scoring distribution will be published right before the start of the contest. We wish you good luck and beautiful solutions!

UPD1. Scoring for div2: 500-750-1000-1500-2000-2500. Scoring for div1: 500-1000-1500-2250-3000.

UPD2. The contest is over, congratulations to winners!

Div1:

1. ainta

2. W4yneb0t

3. Petr

4. muratt

5. kcm1700

6. Vercingetorix

7. Tinsane

8. Reyna

9. aid

10. zemen

Div2:

1. MinamiKotori

2. Ancient_mage

3. WhatTheFua

4. Yanba

5. macieck9

6. OMRailgun

7. radoslav11

8. zhsh

9. skywalkert

10. abgnwl

UPD3. I sincerely apologize for the delay with problem analysis. I was out of town for a vacation. Here it is.

Dear friends!

We are glad to invite you to take part in Codeforces Round #363, featuring some problems of the VK Cup 2016 Final Round that took place in Saint Petersburg at the beginning of July. The second part of the problemset will be used to conduct Codeforces Round #364. Of course, we made some new problems to complete the set to fulfill the requirements of the regular round and it now contains problems of the appropriate difficulty for participants of any color.

We will obey the good old tradition to publish the scoring distribution right before the start of the competition.

We wish you good luck and an interesting contest!

UPD1. Scoring distribution will be standard in both divisions 500-1000-1500-2000-2500-3000 (yes, there will be six problems featured in both div1 and div2).

UPD2. Problems were prepared for you by MikeMirzayanov, Errichto, fcspartakm, qwerty787788 and Radewoosh.

UPD3. System testing is over, congratulations to winners!

Div. 1:

1. Petr
2. Egor
3. jqdai0815
4. semiexp
5. gs12117
6. Vercingetorix
7. ilyakor
8. Marcin_smu
9. Gullesnuffs
10. JoeyWheeler

Div. 2:

1. Out_of_Cage
2. lajiniunai
3. tweety
4. 1e18
5. _Madiyar
6. zoomswk
7. bciobanu
8. FlappyBird
9. IHaveInt
10. amsen

UPD4. Analysis is almost here

— Hey, It's me again. Plain to see again...

— Oh crap, it's PrinceOfPersia again :|

I'm here to introduce you: Codeforces round 362. It's gonna take place on 196th day of 2016.

I'm the writer of this round. Not as always, there are 6 problems. I hope you enjoy.

I want to thank LiTi and Haghani for testing this round, danilka.pro and GlebsHP for helping me prepare the problems and MikeMirzayanov for legendary platforms of Codeforces and Polygon.

The main character of this round is Barney Stinson (high five ;)) and you're gonna help him with his problem.

I wish you all lots of Accepted solutions and hope to see no Skipped solutions ;)

Scoring will be posted soon.

GL & HF!

UPD: We decided that the contest has 6 problems (in each division, 4 shared). Duration will be announced as soon as we decide, but It's gonna be between 2 and 2:30 (inclusive).

UPD1: Duration is 2:15.

UPD2: Scoring is standard in both divisions: 500 — 1000 — 1500 — 2000 — 2500 — 3000

UPD3: Check out the editorial!

UPD4: System testing is over. Congratulations to the winners!

Div.1 Winners are:

1. jqdai0815
2. jcvb
3. sankear
4. matthew99
5. Zlobober
6. Claris
7. Endagorion
8. Reyna

Div.2 Winners are:

1. variance
2. holy_collie
3. kimiyuki
4. O__________O
5. hs484
6. czllgzmzl
7. kimden
8. jtnydv25

Hello, Codeforces!

Educational Codeforces Round 14 will take place on 13 July 2016 at 19:00 MSK for the first and the second divisions.

<I already have a long list of problems, so don't be upset if your problems wasn't used yet>

The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.

If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.

It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks (of course the difficult tasks are also needed). Please send only the problems for which you know the solution with clear statement (the story is not required). And also please add one or two samples to make the problem statement more clear.

Thanks a lot to them and all others who are sending the problems! The number of unused problems are increasing. If I didn't miss anything I already replied to all who sent me the problems at least 5-6 days ago. Please be patient if your problem was not used a long while.

</I already have a long list of problems, so don't be upset if your problems wasn't used yet>

The problemset was suggested by Codeforces users. The problem А was suggested and prepared by user Arthur Jaworski KingArthur. The problem B was suggested by Nikita Melnikov nickmeller. The problem C was suggested by user blowUpTheStonySilence. The problem D and E was suggested by Zi Song Yeoh zscoder (he is on IMO now, so good luck to him). The problem F was suggested Michael Kirsche mkirsche.

As I said the problem A is prepared by Arthur Jaworski KingArthur. All other problems was prepared by me (Edvard Davtyan). Thanks to Tatiana Semyonova Tatiana_S for checking the English statements. The problems was tested by users suggested them, respectively: Arthur Jaworski KingArthur, Nikita Melnikov nickmeller, user blowUpTheStonySilence and Michael Kirsche mkirsche. Thanks a lot to all of them!

I hope you will enjoy the problems! I think the problemset is balanced and not difficult.

Good luck and have fun!

UPD 1: All the hacks for the problem D will be rejudged.

UPD 2: Hack phase will be extended until tomorrow.

UPD 3: Sorry for the problems in the problem D. The solutions that got WA3 were rejudged. The problem is OK now.

UPD 4: The contest is finished. All the solutions were judged on the full testsets. The editorial will be published soon.

UPD 5: The editorial is published.

Hello CodeForces! I'd like to invite you to the online mirror of an open championship of Switzerland called the Helvetic Coding Contest.

The Helvetic Coding Contest is a yearly contest held at the EPFL in Lausanne by the PolyProg association. The contest itself took place in March, but the online mirror is scheduled on Sunday, 10th of July, 11:00 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.

You will help the cow Heidi protect humanity against a zombie apocalypse. The contest will feature 6 series of 2-3 related tasks with increasing difficulty (say easy/medium/hard). Sometimes it may be the case that a solution for the hard version solves all of them, but usually not. In the onsite contest, teams could only access the medium version of a problem once they have solved the easy, and so on; in the mirror, there is no such constraint and you will be able to see all versions since the beginning. (Otherwise, the formats of the onsite and the mirror are the same.) We think that the problemset is diverse and interesting, and while the contest is ACM-style, you will find that some problems are far from standard :)

We promise to publish a very nice editorial as soon as the contest ends.

Acknowledgments: I had the pleasure of coordinating the team of problemsetters for this contest: gawry, Christian Kauth, maksay, boba5551, DamianS and myself. Thanks also go out to people who helped with the statements and testing: Jeremy Rabasco, Valerian Rousset, Sjlver, Wajeb; GlebsHP for Russian translations and 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 AdNovum. 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:

• congratulations to the winners:

1. Zg: gustav, ikatanic

2. Endagorion

3. squark_tutan_RR: ngfam_kongu, I_love_Hoang_Yen, s-quark

4. mehlxneh: AntiForest, JoeyWheeler, xxTastyHypeBeast666xx

5. FTP++: pwypeanut, jacobtpl, zhangguangxuan99

6. Команда, в которой непростые в...ку с максимальным рейтингом: Um_nik, kb., Tinsane

7. Khodaro Shokr: SeyedParsa, PrinceOfPersia

8. Coder

• the editorial is available (PDF); feel free to ask questions here,

• hope you enjoyed the contest!

Hi everyone!

I want to present you the Codeforces Round #361 (Div. 2) that will take place on the 6th of July at 19:35 MSK. The contest was prepared by Gabriel I_Love_Tina Cojocaru and Mihail ThatMathGuy Tarigradschi.

I'd like to thank Dan danilka.pro Sagunov and Gleb GlebsHP Evstropov for their help in preparing the round and for making the round possible,Mike MikeMirzayanov Mirzayanov for the great Codeforces and Polygon platforms.

Good luck in the contest!!

UPD1.In this round you will help our hero Mike solve tasks he encounters every day.

UPD2. Editorial

UPD3.Congratulations to the winners of the round.

Div 1:

1.Um_nik

2.cgy4ever

3.anta

4.HellKitsune

5.ksun48

6.waterfall

7.Kaban-5

8.I_love_Tanya_Romanova

9.I_love_tigersugar

10.RomeoFantastik

Div 2:

1.Sky4teen

2.TudorMiclovan

3.darius.marian

4.Hirasawa_Yui

5.Chloe_fan

6.AnonymousBunny

7.fenchen

8.Grandpa

9.6eJIa9IzZzTeHb

10.raiders7

Hi!

We're glad to invite you all to participate in Codeforces Round #360(Div. 1 and Div. 2) which will take place on Wednesday, 29 June, 20:05 Moscow time. Check it in your timezone!

The problems are designed by Man (Parsa Abdollahi) and me. It's our first Codeforces round and we hope you enjoy competing it as much as we enjoyed preparing it! (^◡^)

Our special thank goes to JeBeK (Peyman Jabbarzade) who helped us a lot in preparing and testing the round. Many thanks to GlebsHP (Gleb Evstropov) for his help in preparing the contest, and MikeMirzayanov (Mike Mirzayanov) for great platforms Polygon and Codeforces. We also want to thank Zlobober (Max Akhmedov) for testing our round.

We wish (and expect!) you all many Accepted solutions! ( ﾟ▽ﾟ)/

UPD: Problems are going to be about Pari and Arya.

UPD2 Congratulations to the winners!

Div. 1:

1. jqdai0815
2. tourist
3. Egor
4. xyz111
5. subscriber
6. riadwaw
7. ainta
8. jcvb
9. Um_nik
10. Shik

Div. 2:

1. Julek
2. polygonia
3. Snipx
4. I_love_littlechild
5. AminAnvari
6. Shayan
7. yashkumar18
8. Archies
9. Clone3
10. lature

Editorial + some challenges will be published soon.

UPD3: The editorial is out!