Today it will be Croc Champ 2013 Finals! Good luck to all participants. And to those who don't participate — enjoy the interesting competition.

Yesterday have finished the trial contest and Code Game Challenge. The winner of Code Game Challenge is ... tourist!

Also pay attention to the Croc Champ 2013 - Finals (online version, Div. 1). It will be a rated round. Note: it will be slightly unsual because we will not hide the standings of the official contest. So some information about difficulties of the problems will be known before the round. The contest duration is 2.5 hours.

Good luck to everyone!

The contest has been finished. The winners are:

• tourist
• Egor
• eatmore

Final standings

Actually me and MaximShipko have arrived yesterday.

During this time we, together with CROC staff, had setup 40 computers in the classroom (so it is pity that most of you will use own laptops), installed Code Game Challenge infrastructure and ready to meet the participants.

Soon it will be [contest:307]. Do not worry it some of the website features will be disable, our main goal is to make onsite-event.

Note that today the participants will take part in unofficial entertaining AI-programming contest.

I'll greet all the participants personally, and now I'm sending rays of sadness to the participants, who will not be able to participate today because of the curriculum.

Testing Round 6 starts on May 11, 2013, 20:00 (UTC). Our goal is to test the platform after recent improvements. All of them are in the Codeforces backend, but they affect many lines of the code.

I invite you to take part in the round. It will be Div. 2 + unofficials from Div. 1. It will contain four-five obsolescent problems. But I think it will be interesting for many of you. The problems contain very weak pretests to force more hacks. It will be unrated round.

Many thanks to participants!

P.S. As it is testing round, we do not guarantee stable work and so on.

Hooray! Yupee! We have finished the complex me-Cormen-ralekseenkov logistic combination and now are ready to pay tribute to the heroes of 2012. This year (thanks, Thomas!) the Cormen Medal laureates are going to get a new Thomas Cormen book "Algorithms Unlocked", signed by the author in addition to the medal, glory and fame!

The 2012 Cormen Medal laureates are:

• tourist (Gennady Korotkevich) — Codeforces Best Coder 2012
  Gennady keeps his first place in the Codeforces rating, continues participating actively and at this point the third place in the round isn’t always a rating improvement for him. We wish Gennady more victories, especially considering that the ACM-ICPC 2013 Finals are so soon!
• witua (Vitaliy Herasymiv) — Codeforces Best Problemsetter 2012
  In 2012 Vitaly dazed us with his interesting problems many times. Due to him, we are experts on all sorts of lucky number and Little Elephant properties. Thanks to Vitaly for the great problems!
• Nickolas (Mariia Mykhailova) — Codeforces Spirit of Community 2012
  Maria, the author of unusual rounds, an active blogger of 2012, has received a new nomination. Maria’s ideas, bright and out-of-the-box, have made the live of the community more diverse and fun.
• Alex_KPR (Alexander Kouprin) – Codeforces Best Blogger 2012
  We all love reading Alex Kouprin’s stories from all sorts of 2012 sports programming events.

Let us remind you that it’s the third year when the Cormen medals has been awarded. It’s the third year when [tourist] has become the best coder and Alex_KPR — the best blogger twice in a row. My favorite nomination, "Codeforces best problemsetter" went to natalia (Natalia Bondarenko) in 2010, and to Ripatti Artem Ripatti in 2011.

We do hope that the last year laureates will amaze us with their talents on in 2013.

As you probably know there are International Workers' Day holidays in Russia in the beginning of May. Am I the only person who see a contradiction here? Workers and continuous holydays!

So I decided that the best way to spend May, 2nd is to do something useful. So meet new languages on Codeforces:

• Python 3 (3.3.1)
• MS C# .NET 4
• Go (1.1 RC1)

Also I made an attempt to setup Clojure, but his AOT nature makes any solution (even A+B) to run for at least 1 second :( I believe it is possible to precompile Clojure solution into bytecode, but I haven't found the way yet. Maybe someone can help me?

There are three days before round. Three days to test new languages. Please write comments in case of any issues.

P.S. As extra bonus — I've updated Python 2 to 2.7.4.

Hi everybody!

Let me remind you that on the 12th of April, at 20:00 the Qualification Round of the All-Russian Programming Championship CROC-2013 will start.

You need to participate in the Qualification Round to make it to Round 1. Contestants who gain a score equal to the 2000-th place finisher score or greater will advance to the Round 1 (also you need to gain positive score).

At the Qualification Round you will find a few problems, roughly ordered by the increasing complexity. During the Qualification Round the problems are judged only on pretests and system testing will take place after the end of the Qualification Round (round continues for 48 hours). The pretests do not cover all possible cases of input data, test your programs carefully! The Qualification Round has no hacks or decreasing values of the problems.

The round will last for 48 hours, but it does not mean that we encourage you to spend all this time solving of problems. We hope that most participants will cope with the problems (or with most problems) in a shorter period of time. This duration of the round is chosen so that each participant could find a convenient time to participate.

Before the end of the round it is strictly forbidden to publish the problem statements/solutions/any thoughts and ideas about them elsewhere. It is forbidden to talk about the problems, discuss the statements and so on. Be honest and let the best men make it into Round 1. When the Qualification Round is over, you can discuss the problems and solutions.

You can register for the round at any time up to its end.

The results of the round will not affect the rating, non-competitive participation in the round is not allowed. However, all tasks will go to the archive after the end of the round.

Best of luck and enjoy solving the problems!

P.S. You can't take part here unofficially. You may register to the Championship here. The working language of the Championship is Russian, but all the problems will be in English too.

Most agile participants have registered before we implemented validation rules around Championship registration. So some registrations will be canceled. Sorry for it — you may register to the Champ and register for round after it.

UPD: Testing is completed. Unofficially qualification cut-off is 950. Participants with at least 950 points advance to Round 1. It can be changed because of cheaters disqualifications.

As the TopCoder TCO 2013 Round 2A did not take place as planned but was moved (with sniper precision) right on the place of the Codeforces Round #177, we decided to reschedule the contest. I have to admit that my first urge was to leave everything as it is — TopCoder knew of Codeforces Round 177 and I cannot approve of such an approach to solving their technical issues. On the other hand, no fault lies on the community, and especially on dear witua, the writer of the forthcoming round. You’d like to participate and the writer is keen on making a round as popular as it gets. Besides, the problem coordinator Gerald would have fallen under much pressure, juggling work and TCO. That’s why the Codeforces Round #177 moves to the time that was initially planned for Round 178, and Round 178 moves a little ahead.

We apologize for the schedule inconveniences and hope to see you among the Codeforces Round #177 participants. It will be fun!

Just quote:

We have given to the students a task to promote algorithms on the web. This is what came up.

Let's share impressions after the contest!

I had a funny moment then 10 minutes before the end my C was failing on assert. This assert means that something wrong compared with naive solution. After unsuccessful attempt to fix it I commented the assert :)

Welcome to the contest of Saratov State U on Petrozavodsk Winter Training Camp 2012-2013. This contest was prepared with diligence and love by jury team of ACM-ICPC NEERC Subregional (Saratov) Contest. Here is the complete list of writers:

• MikeMirzayanov
• Nerevar
• RAD
• e-maxx
• natalia
• NALP
• Dmitry Klenov
• Dmitry Mescheryakov
• Dmitry Stepanenko

Thanks to all of them!

All the authors invite you to take part in the contest virtually in Gym, if:

• You didn't take part in it previously
• You (or your team) is high skilled that you will take part (or took part) on ACM-ICPC World Finals or other high-level competitions. The problemset seems to be hard for not experienced participants.

Hope, you will enjoy the contest!

Contest link: 2012-2013 Petrozavodsk Winter Training Camp, Saratov SU Contest.

Hi everybody!

Have you spent the January as efficiently as we have? Here's a small list of innovations the users can see:

• Now not only the red coders can become coaches. The coders with a yellow handle are now accepted as well, provided that they have taken part in an official Codeforces round no earlier than 6 months ago and have taken part in at least 30 rated Codeforces contests. This innovation roughly doubles the number of potential coaches. So we invite you to check out your new role in the Gym!
• Now it’s absolutely easy to add a Polygon contest to the Trainings. All you need to do is to copy the data from contest.xml from the Polygon system contest interface to contest.xml in the sandbox folder in the Gym (use FTP).
• We’ve added protection against losing data in the Codeforces and Polygon projects’ forms. Now the textareas have a semitransparent ‘Drafts’ button in the upper right corner. You can use it to view or choose some previous versions of the text. The text is saving to drafts automatically. Now if the browser crashes unexpectedly or if you lose the session, that’s not a problem as you will be able to recover your text from the drafts.
• We’ve done some work on introducing the testing message shift from the system to the browser. You can see it on the Status page.The work hasn’t been completed yet and still has some issues, but on the whole it’s a functional system.
• We’ve updated the testlib to 0.8.7: we've boosted the performance of the ensure() function, the readStrictDouble stopped classify more-than-20-digit numbers as invalid, we’ve fixed some compilation warnings and fixed the compilation for some exotic cases.
• The Polygon system has better performance for problems with large manual tests.
• The contest and problem statements in the Polygon system now have reasonable URLs.
• We’ve fixed some bugs caused by cases in some old problems when the standard checker updates automatically, but testlib doesn’t. As a result, the checker cannot be used in such a problem, as it does not compile with the outdated testlib.h. Just in case, we’ve introduced the autoupdate feature for testlib, now updating it is going to be really easy.
• One more Polygon improvement. If a solution is marked as Main or Correct in the Polygon system, but it gets OK on a test in more than half of the time limit, then such situation gets highlighted in the invocations. Similarly, the system highlights the situation when a TL-solution gets TL, but it gets an OK in the double time limit.
• The problem descriptor in the Polygon system got attribute for the sample (example) tests. Now test element has attribute sample="true" value, if it is the test from the statement. This attribute is optional, it its absence is equivalent to sample="false".
• The compilers on judge servers have been updated to modern versions.

Codeforces Testing Round 5 starts on Jan. 12, 2013, 15:00 (UTC). Our goal is to test the platform after recent improvements. You may notice that we've improved real realtime status. You may visit (problemset status)(http://mirror.codeforces.com/problemset/status) and find that it updates automatically without page reloadings. It uses modern web realtime technologies like websockets and so on. For sure, no server polling!

Also we've updated server software and built Codeforces with Java 7.

I invite you to take part in the round. It will be Div. 2 + unofficials from Div. 1. It will contain three obsolescent problems. But I think it will be interesting for many of you. The problems contain very weak pretests to force more hacks. It will be unrated round.

Many thanks to participants!

P.S. As it is testing round, we do not guarantee stable work and so on.

Calendar: (c) 2011 Anatoly Rr

The Codeforces project wishes all its users a successful New Year. May all your handles change the colors only towards red, may all your solutions go well without debugging and may you enjoy many times the coveted Accepted at each contest! We wish you good luck in everything you do next year — isn't that great to have luck on your side!

Traditionally, the Codeforces enables the users to change their handles. Note that this is a one-time change and you won't be able to return to the previous handle. Analyze all 'for' and 'against' carefully as the handle is what you are going to be often called by the numerous participants of the Codeforces contests.

We've got more good news. We've decided to increase the list of people who can get the role of the 'coach' in the Codeforces project::training. Check out all those training sessions! Now this role can be given to those who:

• have got the red color handle (i.e. the rating of at least 2200),
• have got the orange color handle, have participated in a Codeforces official contest not more than six months ago and have taken part in at least 30 rated Codeforces contests).

This innovation is going to increase the number of potential coaches roughly by two!

And the last, but not the least detail. Now we can increase the authors' fees for preparing contests. That will hopefully give a little motivation to those who can make an interesting round. In 2013 the authors' fees is:

• preparing a Div.1 + Div.2 round (USD): 250 + 50*,
• preparing a Div.2 round (USD): 100 + 50*.

(We use fixed rate USD = 40 rubles, so actual payment may differ slightly). The sums with asterisks are the extra bonuses the author gets for 'good quality'. The author receives the bonus if he worked without jeopardising the deadlines for preparations and the round went without any major problems with the statements (no additional major notices, fixes in solutions/tests/checkers/validators etc.).

We hope to work with authors efficiently in 2013, we hope that our best participants will generously dazzle the community with interesting contests! For more information or to organize a context, please message Codeforces problem coordinator Gerald (Gerald Agapov).

Happy New Year!

Happy New Year!

The New Year is in a two-day distance from us and it's good time to summarize the ending year. In a nutshell, this year's been highly productive for the project. Codeforces has set up large championships, rounds followed one after another, we've launched the Codeforces::Gym project, we've added numerous improvements/fixes/innovations. Here's a short list of our deeds:

• when a user votes for a post/comment, his/her authority is taken into consideration, we've introduced anti-bot and froud-detection heuristics
• the Codeforces::Gym has been opened and has come through many improvements
• the Codeforces Markup, based on Markdown has been introduced, accompanied with special Codeforces tags
• Codeforces helped VK.com to carry out a amplitudinous VK Cup 2012 championship which had around 6000 participants!
• the CROC company has used the Codeforces company to carry out the Open Moscow City and Moscow Region Programming Championship, around 1500 participants!
• the ABBYY company has used the Codeforces platform to carry out the ABBYY Cup 2.0 championship, around 2000 participants!
• we've introduced attaching blog posts to contests as announces, tutorials etc.
• we've semiautomatically attached the tutorials for the past contests
• the Bayan company has used the Codeforces platform to carry out the sorting stage of Bayan Programming Contest 2012/13, more than 3000 participants!
• the CROC company has used the Codeforces platform to carry out the CROC Programming Championship among the Bauman MSTU, around 2000 participants!
• the testlib.h has come through numerous improvements
• we've supported new programming languages
• we've supported the dynamic problem complexity
• we've supported inserting photo albums from Picasa to posts
• we've supported interactive problems — despite the short wording, this point is hugely important
• the Polygon project has come through numerous improvements
• we've supported problems with the score in points and with partial solutions (for the marathon type contests)

And that's not the end! We are glad to demonstrate to you wonderful pictures with pleasing graphs and charts.

Northeastern European Regional Contest 2012 will start on December, 2nd. We wish good luck to the teams and many joyful moments to the funs!

Useful links:

• standings
• Petr Mitrichev blog
• Online translation of Awards Ceremony

NCPC (Nordic Collegiate Programming Contest) — the annual programming competition for universities and colleges in the Nordic countries. The event itself is organised in a distributed manner. It is physically hosted at many participating universities and colleges. The same problemset is used at all sites. The scores are gathered electronically, and the result is simultaneous local, national and Nordic championships.

The organizars publish the problems and testdata, special thank you to the organizers.

The contest of this year is available in Codeforces::Gym — 2012 Nordic Collegiate Programming Contest (NCPC)

It is really good contest as a training before the Subregional or Regional ACM-ICPC contest.

Right now the onsite contest is in progress. You can view the curreny results here.

On Monday you can take part in unofficial contest mirror on http://acm.sgu.ru/. The contest starts on October, 22 (Monday), 2012, 12:00 (UTC). The official results will be integrated into the online contest standings. Hope to see you on [http://acm.sgu.ru/]!

Later the contest will be added as a training in Codeforces::Gym.

Recently the first third team NEERC Trains was finished. By the way, the first place got the intriguing team "SPb NRU ITMO 1: Kever, Korotkevich, Nigmatullin" :-) It was used Warsaw contest from old contest Petrozavodsk camp.

I've added 2007-2008 Petrozavodsk Winter Training Camp, Warsaw Contest to the Gym. The ghosts are not only Petrozavodsk camp participants (2008) but also modern ITMO teams!

Enjoy the contest before ACM-ICPC Subregionals and Regionals contests.