Hello,

I know that the news will upset some of you: the round was moved 1.5 hours forward and it will start on 17:00 UTC.

As for me — the reason is very pleasant. The round original time coincided with a sniper's accuracy with the celebration of my daughter's birthday. Oh, St. Dijkstra, Tatyana is 2 years old! Last week I did many changes in judging backend (around caching) and I don't want in case of some issues to have a choice — to have a bad round or to have a bad celebration. I hope you understand!

Also I'm sure that new time will be more comfortable for some of you.

Hope to see you on the round!

Welcome to 2013-2014 CT S01E09: 2011 German Collegiate Programming Contest (GCPC 2011) + GCJ 2009 R3 C-D. The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Welcome to 2013-2014 CT S01E08: 2013 ACM-ICPC Rocky Mountain Regional Contest (RMRC 2013) + GCJ 2009 WF C-D. The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Hello,

Did you already notice that this Sunday it will be Internet-version of 2013-2014 ACM-ICPC, NEERC, Southern Subregional Contest? It will start on 07:00 (UTC).

The contest will be held in Gym. I invite teams mostly because the contest was designed as a team contest.

I'm sure this contest is a great way to train before coming regional (or subregional for some of you) ACM-ICPC contest.

Welcome to 2013-2014 CT S01E07: Codeforces Trainings Season 1 Episode 7. The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Welcome to 2013-2014 CT S01E06: 2002-2003 ACM-ICPC Northwestern European Regional Contest (NWERC 2002) + Some Problems from COCI and POI. The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Welcome to 2013-2014 CT S01E05: 2007 Nordic Collegiate Programming Contest (NCPC 2007) + Selected Problems from 2009 Google Code Jam World Finals (GCJ WF 2009). The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Welcome to 2013-2014 CT S01E04: 2013 Kashan Contest + Some Problems of 2009 Google Code Jam World Finals (GCJ WF 2009). The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

The most problems were given by mohammadrdeh. Thanks! It is the great help. Take example!

Good luck!

Recently we’ve changed the contribution formula. Now it reflects the current social activity, that’s why all votes for posts and comments are divided by two every 180 days. On the one hand it helps to distinguish the currently active Codeforces members, on the other hand it makes the contribution top more dynamic and opened for the newcomers.

For example, now Egor is the leader of the contribution top because of the (mostly) many interesting posts about ACM-ICPC World Finals. But it looks like 9 months after the World Finals, he can loose the first place.

Also I’ve made some changes with the votes:

1. Now the negative score is not shown (just 0) if it is in range [-5,-1]. I did it because many of you downvote just because you see the negative score.
2. Visualization of vote in comments.
3. Changed some rules to transform votes to contribution, but it is a monotonic function anyway.
4. A comment becomes partially transparent if it has -10 or less (it was -5).
5. A comment becomes hidden with the message about too negative feedback if it has -25 or less (it was -10).

I hope you we will do same changes as in items 1-2 for posts.

Welcome to 2013-2014 CT S01E03: selected problems from 2002 Central European (CEPC 2002) + 2010 Southeast USA Region. The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration will be available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Welcome to 2013-2014 CT S01E02: Extended 2003 ACM-ICPC East Central North America Regional Contest (ECNA 2003). The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

The registration is available on the Gym page and will be opened until the end of the training. Be careful registering team: please, choose only whose members who will take part in the contest.

Good luck!

Welcome to 2013-2014 CT S01E01: Extended 2000 ACM-ICPC East Central North America Regional Contest (ECNA 2000). The training duration is 5 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

Good luck!

The new season of a collegiate team championship ACM-ICPC is about to start. For example, the registration for the Southern (Saratov) Subregional Contest is already running. I am sure that many participants of the Codeforces rounds will take part in ACM-ICPC this year.

We are launching a series of weekly practice trainings on Codeforces. Naturally, they will be held within Codeforces::Gym. Feel free to participate!

The practice starts at about 12:10 PM (UTC), which is 16:10 Moscow Time. We are going to practice using the problems of different contests of the past years. All you need is common sense and observing these simple rules:

• We will not publish the problem source before the practice starts. We want you to solve the problems on your own in a fair competition. If you use somebody else’s code or cheat in any other way, you will be disqualified. If you don’t want to solve on your own, that’s fine, you don’t have to. But spoiling the practice for others is unacceptable.
• Do not discuss the problems till the practice ends.
• We will rarely answer the questions about problems. If you’ve found some obvious bug, please let me know. We will fix the bug and send everybody the note about the fix.
• If you have a coach account (and you do not participate in the practice), we will be grateful for your help.
• Please register for the practice with the people from your team who actually participates in it.
• From time to time, I am going to ask some of the jury of the past contests or coaches from other higher educational institutions to help with preparing or share materials — your understanding and help will be greatly appreciated!
• if you solved the contest problems before just switch to another training or inform us via problem questions form, we will move you to out-of-competition role.

The first practice takes place on September, 11, at about 12:10 PM (UTC).

With the help of some experienced and respected members of the community (thanks!) there was formulated a rule that allows a third party code to be used under certain conditions. Please read carefully the text.

The following text will go as part of a renewed competition rules. The closest contest will be held already on the updated rules. Thus, there are about two days for further details, if something is unclear.

Solutions and test generators can only use source code completely written by you, with the following two exceptions:

1. the code was written and published/distributed before the start of the round,
2. the code is generated using tools that were written and published/distributed before the start of the round.

Any usage of third-party code should not violate the right holder’s license or copyright. Remember that published code is not always free to use! At the request of the right holder, any code that violates the license or copyright may be considered as violating the rules.

All the changes in the code from exceptions 1) and/or 2) must be made solely by you.

If there are any doubts about the time of publication, possible collaboration etc., a participant will have to prove his/her complete innocence by presenting compelling and satisfactory evidence.

Currently, the only reliable proof is the presence of code on the Internet and the presence of the used edition in the cache of well-known search engines.

For example, this rule accepts the use of the code from the website http://e-maxx.ru/ if the code was written and published/distributed before the start of the round. With the help of search engine caches, it can be easily shown that such code doesn't violate the rules. Similarly, it is permissible to use the code from a book/article that was published before the contest. On the other hand, using team reference code (for example, prepared for ACM-ICPC World Finals) is not allowed if there is no reliable and objective way to prove that the code was written before the contest.

This rule doesn't loosen the rules about prohibiting of communication, discussion, or any other form of communication between the contestants on any topics about the problems during the round.

Rah-rah!

We are moving forward to accelerate testing. In fact, when our rounds attract 3500+ registrations, it is hard to test all the submissions on nine computers "Core 2 Duo E6750, 2.66 Ghz, 3Gb".

Computer Science Department of Saratov State U has recently got 20 new computers i5-3470, 8Gb. After a little research it was found that if boost CPU to 3.5Ghz (of course, turning off all sorts of turbo boost and after many hours of stability check), the speed is approximately equal to twice the speed of the old testing machines. This is very convenient as it will in future only to divide all the time constraints in the problems by 2.

We have moved to testing on new computers and we do it in compatibility mode. This means that all the time constraints before the start of the program are divided into 2, the program is executed, and at the end a running time is multiplied by 2. In fact, if you do not use the cut-off by time or some other unsavory stunts, you will not detect any changes.

Old testing machines are switched off now.

To be very precise, the new computers are not so fast as 2x old. That is in compatibility mode it is normal to notice a slight degradation in speed.

ABBYY Cup 3.0 — Finals is about to begin. We wish good luck to all the participants!

You may view the current contest standings here.

We do not want the rest to get bored. So ABBYY and Codeforces conduct an unofficial online version of the contest today at 15:30 UTC.

This round will be:

• rated
• for both Div.1 and Div.2
• 2 hours duration
• on the modified ACM ICPC rules (problems are divided into subproblems, count only complete solutions of subproblems, there is a score for each subproblem, a penalty is charged by the rules of ACM ICPC)

Good luck!

Hello.

If you are not sleeping now, join to Testing Round 8. Thanks!

Thank you for participation. See you tomorrow on MemSQL start[c]up Round 1.

Our community keeps on growing and gaining in popularity! We are glad to announce that Codeforces has recently registered its one hundred thousandth user. Thanks to everybody who keeps the project going — the problem writers, testers, corporate partners and of course all members of the community. Our special gratitude is to the VK.com company!

One cannot get enough of the good statistics. Here are some more numbers:

• our database contains more than 3.5 millions of your submitted solutions,
• the number of problems comes near 3000,
• the number of site visitors per month excedes 400000,
• the number of page views per month amounts is approximately 5000000.

The first information letter

General information

In the first part of August 2013 Saratov State University runs an international student summer school in computer programming. The exact dates are 5-15 of August. Teams of three people and individual participants are invited to take part in it.

The school will take place in a picturesque place at one of Saratov resort centers on the Volga bank. The participants will be provided comfortable rooms for 2-4 people and meals three times a day. The resort center owns a beach and sport grounds.

It will be 10 training days. The school includes lectures by Saratov state university coaches, joint trainings, problems tutorials and topical workshops. The curriculum is designed for younger university students who aspire to achieve high results at programming competitions. Official language is Russian.

The fees are 16500 RUR (~ 525 USD) per a person. Moreover, each team or an individual participant should bring a laptop with the support of WI-FI.

All interested participants and teams should register at http://goo.gl/DHwqU till 15th June 2013. Don't postpone the registration, as the number of participants we can take is limited.

You can get additional information by e-mail mirzayanovmr[symbol-at]gmail.com. As since the official language of the school is Russian, the registration requires knowledge of Russian. Also it is recommended to view this page in Russian.