Will begin today, at 21:00 MSK. All paricipants, advanced to the elimination stage, are welcome to participate through the link. This round will be 100 minutes long and will be scored using Grand-Prix 30 system. First place in Round 1 gave pperm86 100 score points and invitation to the final round in Berlin! Who will reserve his place among the finalists today?

Good luck!

P.S. In case of infinite redirect loop, please, clean browser cookies or use an incognito mode

Hi everyone,

Codeforces round #251 for division 2 participants will start at June 4, Wednesday, 19:30 MSK (usual time). Traditionally we invite Div.1 participants to take part out of the competition.

The round was prepared by me (PraveenDhinwa). This is my first codeforces round. I have tried my best to make the problem statements as clear as possible. I hope that everyone will enjoy the round.

Special thanks to Gerald(Gerald), for his extensive help in problem ideas verification, problem testing, without his help the contest would not have seen the day. English translation is done by me with a lot of help from Gerald Agapov(Gerald). Problems are translated in Russian by Maria Belova(Delinur).

Many thanks to Pratik Moona(pratikmoona), Varun Nitish(JuanMata) for providing their help in testing of round. Their help is greatly appreciated :)

Many thanks to Devendra Agrawal(devu)Utkarsh Lath(utkarshl) to helping me in verifying the ideas of problem statements.

Many thanks to Mike Mirzayanov(MikeMirzayanov) for creating this wonderful platform :)

The contest problems are dedicated to my dear friend Devu (devu), He once proposed problem titled "Churu, the thief". Churu is my nick-name. So it is now time to take some revenge in a funny way :P

Score distribution for the contest is standard: 500-1000-1500-2000-2500.

I have a good news for you too. Tutorial of the contest will be available as soon as the contest ends :).

I wish all the participants good luck, high rating and lot of hacks :) Don't miss the round.

UPD Thank you everyone for participating. I hope that you have enjoyed the round, Thank you all !!

Editorial

We've introduced API and now we want to test the system before Round 251.

I invite you to take part in Testing Round 10. It starts on usual time, June 3rd. It will be unofficial unrated round.

I tried to pick up the problem to make the round interesting for many of you. Pretests are unusually weak to trigger more hack.

If you see any unexpected behavior or bugs, please inform us via comments.\

Thanks.

Hello, Codeforces!

Today we want to introduce Codeforces API. With it you now can access some of Codeforces data in machine-readable JSON format.

API has a detailed manual, which is supported to contain only actual information. Every method has an example URL. You can use it to see the example response and to experiment with different parameters.

By default, any API request will be anonymous and will have access only to public data. To make a request on behalf of some user, a user must create an API-key at /settings/api and read the bottom part of the manual at /apiHelp.

For now, all methods are read-only. Write-methods like "submit a solution" are coming soon.

We are open to suggestions and requests for new API-methods. Especially from respected members of contest programming community.

With best regards, Ivan.

Happy Children's Day everyone. What should you do to celebrate the special holiday?

Of course, another Codeforces Round is your best choice!

There is a child who is our friend. Now he has faced a lot of algorithm problem, could you please help him?

We invite you to participate in Codeforces Round #250, which will take place at 17:00 MSK on 6.1 — Children's Day. This round will be held in both divisions.

Note that the starting time of this round is quite unusual.Why? Because it's yet another CF Round held by Chinese! We prepared many interesting problems for you.

Are you getting excited? Don't miss this round!

The problems were prepared by delayyy, Picks and me. This is our first Codeforces round~~~~.

Many thanks to Gerald, who gave us enormous help during the preparations for this round; to ftiasch, Kissshot and jqdai0815, who are the testers of this round; and to MikeMirzayanov, who created such a wonderful platform.

In Div. 1, scores for each problem will be 500-1000-1500-2000-3000.

In Div. 2, scores for each problem will be 500-1500-1500-2000-2500.

Look! Your high rating is waiting for you! What are you waiting for?

Just participate in this contest and write code fast and nicely, and you will take the high rating home!

Good luck and have fun!

UPD: The contest is over! Congratulations to winners!

Top 5 of Div. 1:

1. Alex_2oo8

2. Petr

3. Dmitry_Egorov

4. TankEngineer

5. al13n

Top 5 of Div. 2:

1. tohdon

2. KFDong

3. function348

4. 104325EA

5. Boyuede1

Unfortunately, no one has solved the problem E in both divisions. What a sad story....

Editorial for the round will be added soon.

UPD2: Editorial for the round can be found here: Editorial

Hi all)

Tomorrow at usual time will be held regular Codeforces round #249 for Div.2 participants. Traditionally we invite Div.1 participants to take part out of the competition.

The problems were again prepared by authors Pavel Kholkin (HolkinPV) and Gerald Agapov (Gerald). As always, we express our gratitude to Michael Mirzayanov (MikeMirzayanov) for perfect Codeforces and Polygon systems and Mary Belova (Delinur) for translating the problems.

UPD: Score distribution will be standard — 500-1000-1500-2000-2500.

We wish all participants good luck, high rating and enjoyment of solving problems)

UPD2: the contest is over, we hope you enjoy it)

UPD3: link to editorial is already here)

UPD4: Congratulations to winners!:

1) JiangZemin_JiangHaha
2) Rafbill
3) Yukinoshita_Yukino
4) kuangbin9
5) spartacus

We’d like to invite you to take part in the qualification round of the Yandex.Algorithm competition that will start on May 25, 2014, at midnight. You need to start your qualification within 24 hours from the beginning of the qualification round. Qualification will last 100 minutes.

To advance to the next stage of Yandex.Algorithm you will need to solve at least one problem during your qualification.

Participants, already advanced to the elimination stage from warm-up round, are also welcome on the qualification.

Good luck!

Hello everybody!

We invite you to participate in Codeforces Round #248, which will take place at 11:00AM MSK on Saturday, May 24th. This round will be held in both divisions. Note that the starting time of this round is quite unusual.

The problems were prepared by zhonghaoxi, wyx528 and me. This is our first Codeforces round and we hope it will be a good one.

Many thanks to Gerald, who gave us enormous help during the preparations for this round; to colin and MSTyoda, who are the testers of this round; and to MikeMirzayanov, who created such a wonderful platform.

In Div. 1, scores for each problem will be 500-1000-1500-2000-3000. In Div. 2, scores for each problem will be 500-1500-1500-2000-2500.

Hope you enjoy the problems! Good luck and have fun~

UPD: Contest has finished! Editorial for the round can be found here: Editorial

UPD2: System test has finished! Congratulations to the following winners!

Top 5 of Div. 1:

1. YuukaKazami
2. KADR
3. RAVEman
4. Seyaua
5. ikatanic

Top 5 of Div. 2:

1. jason_yu
2. Kann
3. tomsyp
4. keavil
5. Kazakh_Alga

YuukaKazami is the only contestant to solve problem D! Sadly no one solved problem E during the contest.

UPD3: Statistics of the round by DmitriyH is here: Statistics