By andrewzta3 days ago, translation, In English,

Russian Code Cup is a competition organized by Mail.Ru Group for Russian-speaking programmers. This year the competition will run for the fourth time to gather top 50 to great finals in Moscow in October.

Though Russian Code Cup is open only for those who speak Russian, the team that is working on problems for Russian Code Cup has decided to make a present to all CodeForces users and set up an extra round for everyone.

The round will be held on April 17 at 19-30 Moscow time. The round will be open for everyone and will have both div-1 and div-2 tasks. It will use standard CodeForces rules. The writer of most problems is Aksenov239 — author of many Russian Code Cup problems.

We wish all participants good luck and see you on Thursday at

Read more »

  • Vote: I like it  
  • +164
  • Vote: I do not like it  

By Gerald2 days ago, translation, In English,

Good day!

Codeforces will hold competition Coder-Strike 2014 for Moscow school children. Qualification Round of the competition will start soon. The round will be unrated for all participants.

As usually, anyone can enjoy the problems! If you aren't a Moscow school child you can take part in the round unofficially.

Hope you will enjoy our problems, good luck!

Read more »

  • Vote: I like it  
  • +32
  • Vote: I do not like it  

By MikeMirzayanov4 days ago, translation, In English,

The round will start on 08:00 (UTC) of April, 13. It will be a kind of unusual round because at first for a long time Gerald didn't work much on round. It was prepared by me (how it is interesting to write a round!), Nerevar with the help of Gerald and Fefer_Ivan-а. Maria, many thanks for translations!

It will be classical points: 500 — 1000 — 1500 — 2000 — 2500.

Read more »

  • Vote: I like it  
  • +129
  • Vote: I do not like it  

By matrix11 days ago, In English,

Hi everybody!

Codeforces round #240 will take place tomorrow 19:30 MSK

This is our first round in Codeforces and we hope that everything will be fine. The problems were prepared by Amir Keivan Mohtashami(matrix), Farbod Yadegarian(FarbodY) and Gerald Agapov(Gerald). Also special thanks to Mohammad Amin Khashkhashi Moghaddam(alex-mercer) for testing this round.

I want to also thank MikeMirzayanov for Polygon and Codeforces systems, and also Maria Belova(delinur) for translating the statements.

We wish you a good and challenging round.

Have fun!

Score distribution:

div1: 500 — 1000 — 1500 — 1500 — 2500

div2: 500 — 1000 — 1500 — 2000 — 2500 (standard)

UPD: due to technical reasons the round was delayed for 10 minutes. We apologize for any inconvenience caused.

UPD2: Congratulations to the winners!

Div 1:

  1. louise

  2. sankear (The only one who solved problem E during the contest. Congratulations!)

  3. Egor

  4. qwerty787788

  5. hos.lyric

Div 2:

  1. jzzhu

  2. SJTU_WengJian

  3. alcot

  4. LoveEvita

  5. huyifei

  6. NiuYiqiang

UPD3: The round analysis are prepared by DmitriyH. You can find them here.

Also the tutorial is not completely ready yet. But you can find some notes about some of the problems here. I'll try to complete it as soon as possible.

Read more »

  • Vote: I like it  
  • +286
  • Vote: I do not like it  

By MikeMirzayanov12 days ago, translation, In English,


I think everybody can remember a case when

Probably everyone remembers in practice a case when after implementation of correct algorithm you receive Wrong Answer. In such a situation, sometimes works: to send solution on another compiler.

Gerald and Nerevar have found severe bug, which gives one more argument to use the rule above.

Look closely, now it will be a miracle! 

Read more »

Tags bug, g++
  • Vote: I like it  
  • +250
  • Vote: I do not like it  

By Fefer_Ivan2 weeks ago, translation, In English,

Hello, Codeforces.

UPD: Round is finished. Thank you for your participation. Final results.

Today (16:00 UTC) we want you to take part in testing and unrated round with unussual scoring system. With your help we want to test new scoring, new type of problems and Codeforces system inside <iframe> tag.

Start time is 16:00 UTC

Go to the Contest!

There are two types of problems: logic puzzles and programming tasks.

A logic puzzle is a task that is designed to be solved by hand (but it is not forbidden to write some helper code to do this). Each logic puzzle consists of one or more tests. Each question can be answered separately from the others. There is a "Submit" button below each test. To answer the question, press "Submit" button. Your answer will be acknowledged and checked after the end of the contest. You can change your answer any number of times – only the last attempt is checked. For the correct answer to the question you will get the number of points which is indicated in the question description.

A programming task is want you can ussually see in Codeforces rounds. Solutions can be submitted at any time during the contest. A solution is evaluated on a fixed set of tests right after it is submitted. For each passed test, a contestant will get a fixed amount of points. The sum of points for all passed tests is the total points received by the solution. The contestant can submit a solution several times. The contestant will receive points for only one solution per problem. The solution with the maximum amount of points will be chosen.

The contest period is divided into two sections: Normal Time (NT) and Extra Time (ET). Each contestant is in only one of these at a time, but which one you're in can vary per contestant. In other words, when one contestant is in Normal Time, another one could be in Extra Time.

  • Normal Time lasts for at most 30 minutes starting from when you click the button "Start Contest". (It could be less than 30 minutes if you start the contest less than 30 minutes before it ends). Points gained in Normal Time are the main way of deciding who wins. A participant with more points gained in Normal Time will always have a better ranking than a participant gaining fewer points in Normal Time.

  • After Normal Time ends you can still solve problems until the contest ends. This period is called Extra Time, and points gained in Extra Time are the second way to order contestants. Thus points gained in Extra Time are used to rank participants that have the same number of points gained in Normal Time.

If a pair of contestants have the same number of points gained in Normal Time and the same number of points gained in Extra Time, they will be ordered according to the time (in seconds) of the last submission which gave them an improved positive score. For each programming task, we will consider only the best submission (or if there are many submissions which are equally correct, the earliest). For logic puzzles, if you submit new answers in Extra Time, whatever score you would have got is over-written by your new submission, and those points are changed into Extra Time points.

In other words, it's always safe to submit a new answer for programming tasks (you can only improve your situation). It is not always safe to do that for logic puzzles – consider carefully whether or not you want to do that.

The problems will be relativly easy but, I hope, they will be interesting, as will be the contest format.

We will be greatful for all community members who help us in testing.

With best regards, Ivan.

Read more »

  • Vote: I like it  
  • +109
  • Vote: I do not like it  

By Nickolas2 weeks ago, translation, In English,

Unfortunately, the most anybody could solve was 7 problems out of 9 total. 1289 participants solved at least one problem — this is less than the last year's numbers, but not bad either. Anyways, the key point is the total quantity of fun the people had!

409A - The Great Game

The Most Intellectually Challenging Game In The World turned out to be the famous rock-paper-scissors. One could deduce this from the examples — ok, the rock () didn't look itself, but paper [] and especially scissors 8< looked really lifelike!

Team competition is organized like this: players are split into pairs, with one player of each team in each pair, and pairs play against each other (the first line of input has "moves" of first team's players, the second line — of second team's players). The team which scores more individual victories wins.

By the way, the game is not so trivial as it looks -

Read more »

  • Vote: I like it  
  • +137
  • Vote: I do not like it  

By Nickolas3 weeks ago, translation, In English,

The contest is over; I hope you've enjoyed it :-) Editorial is here. See you next year!

The third April Fools Day Contest will take place on Tuesday April 1st. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is. Thanks to kit1980, Skiminok, Gerald and MikeMirzayanov for their help in preparing problems.

In this round you'll be given several weird problems (the estimated quantity is between 6 and 10) and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces — well, unless the problem says otherwise :-)

Be warned, to enjoy competing in this round you'll need a sense of humor compatible with mine! Good luck, and have fun!

Read more »

  • Vote: I like it  
  • +370
  • Vote: I do not like it  

By izban3 weeks ago, translation, In English,

Hello everyone!

This Sunday, on March 30 at 11:00 MSK (March 30 at 07:00 UTC), Codeforces Round #239 for both divisions participants will take place. Note the unusual time of the round.

The problems have been prepared by me. I want to thank Codeforces team: tasks coordinator Gerald Agapov (Gerald) for invaluable contribution to the preparation of tasks and Maria Belova (Delinur), who has translated the problems. Also thank to Niyaz Nigmatullin (niyaznigmatul) for testing.

I wish you all good luck and have a good weekend!

UPD: You can see score distribution at the problems page.

UPD2: You can find editorial here.

Read more »

  • Vote: I like it  
  • +228
  • Vote: I do not like it