Hello

We've scheduled Codeforces Testing Round #4 on January, 3 15:00 (UTC). It will be non-rated event, just to test system before important Codeforces Round #100. The round duration is 1 hour and it will contain just two problems. I do not promise something interesting and exciting, but as a small warm-up will be nice :)

I'll be glad to see you on the round,
MikeMirzayanov

The testing is successfully completed. Thank you for participation. I hope you like this sprint.

Codeforces project congratulates everybody who is into sport programming with New Year! A New Year is not just an increment of a year. Let this day be a starting point to your new achievements, accomplishments and success. Codeforces wishes you to find out by the end of 2012 that all your resolutions have been a success! We wish you to have interesting problems, nice solutions, correct code and more and more of beautiful green messages  Accepted.

As well as in the previous year, we enable handle change for ten days. The handle change is available from the "Settings → Handle" tab from your profile page. Handle change will be disabled on January 10, so don't lose the moment!

Happy New Year, Happy New Coding!
MikeMirzayanov

Hi everybody!

The calendar shows the end of December — the year 2011 is about to end. It was an eventful and exciting time for us. You can find pictures below summarizing 2011 in comparison to 2010. In a nutshell, we've made it! We have grown in all parameters! This result is the shared victory of the well-united team. My special thanks go to the VK (VKontakte) and specifically — to Pavel Durov. The programmers' community and its development really matters to them. I want to thank the authors of the problems: preparing contests is tough and you are a significant help to the Codeforces project and to the whole community.

So, comparing the ending 2011 year and the 2010 year in pictures goes like this:

Codeforces users' growth throughout the Codeforces history (by months)

Hello, everybody.

New Year Holiday is a time of miracles and gifts! Quite by chance the 100th Codeforces round coincided with this wonderful moment.

So, January 4 at 15:00 (UTC) the anniversary Codeforces Round 100 will have place. Yes, we say goodbye to the word Beta in round titles :)

It will be a combined round, that is, participants Div1, Div2 and newcomers will compete with one set of problems. To make it interesting for each participant we plan to expand the round to 6 problems.

The most important thing: the best hundred participants of the 100th round will receive an exclusive Codeforces t-shirt!

Happy new year!
Codeforces Team

Informal unrated contest Codeforces Testing Round #3 is scheduled on December, 2 (Friday), 15:00 (UTC). We will test the latest innovations on Codeforces that they do not affect the contests. If not, we will fix it quickly :) So, this round will take place "as is", no warranty about it.

Problems for the round may be famous to someone, but I'll try to make them such not for any of you. It will be 3-4 problems, as quite simple and something more tricky. The contest duratiuon is 1 hour.

I say thanks in advance to all those who will come and test the system. Thank you!

The ACM-ICPC Northeastern European Regional Contest 2011 is over. Congratulations to the winners! I especially want to mention the team that will represent our region on the World Finals in Warsaw:

1. SPb NRU ITMO 1 (Kapun, Kever, Nigmatullin) — 1-st place, champions
2. Moscow SU 1 (Fedorov, Kaluzhin, Rogulenko) — 2-nd place
3. Belarusian SU 1 (Bahdanau, Pisarchyk, Sobol) — 3-rd place
4. Saratov SU 2 (Ivanov, Kuznetsov, Rakhov)
5. SPb SU 1 (Andreev, Boykiy, Fondaratov)
6. Moscow IPT 1 (Dlugach, Gimadeev, Shishkin)
7. Ural FU 1 (Dolgorukov, Schelkonogov, Soboleva)
8. Altai STU 1 (Silin, Uvarov, Yesipenko)
9. Ufa SATU (Lezhankin, Mazgarov, Ripatti)
10. Nizhny Novgorod SU (Lyulkov, Shmelev, Vadimov)
11. Belarus SUIR 2 (Berezhnov, Brukau, Ropan)
12. Udmurt SU (Abizyaev, Kibardin, Urbanovich)
13. Latvian U 2 (Kalinicenko, Vihrovs, Vilcins)
14. Kazakh-British TU 3 (Aitbayev, Satylkhanov, Almakhan)
15. Tomsk SU 1 (Chadnov, Kolupaev, Afanasev)
16. Volgograd STU (Agafonov, Chalyshev, Zhorin)

Codeforces wishes all future World Finals participants the success in preparing for the competition and good results in the final!

Hello!

On Friday, November 25 at 19:00 I'm waiting you on the Codeforces Beta Round #95 (Div. 2). This round is prepared by me. It is not easy to prepare a round, but it is always useful and interesting. By my example, I want to hint to top participants that rounds of famous people — it's always interesting!

Apart from me RAD, Nickolas and Delinur were doing work on the round. Moreover, Edvard still do not know, but very soon I will ask him to solve this round as a tester:)

It will be unusual round because you will find six problems. It's a little experiment — I hope that it will help each participant to find interesting problems to themselves.

I believe that the out-of-competition participants from Div.1 will have some fun solving the round.

The problem scoring is: A - 500, B - 1000, C - 1500, D - 2000, E - 2500 and F - 2500.

Good luck!

MikeMirzayanov

UPD. The competition has ended. Here are the results. First place was taken by the representative of China — liuq901. Congrats! It was nice to see such interest to the contest. Thank you for your participation!

Unfortunately, I do not have the opportunity to write a tutorial. If you deal with it I will be grateful.

Hello.

I want to share a great joy of my family. On the night of the 8th to 9th November, a little girl named Tanya Mirzayanova was born. Of course, now the reasons of round shifting are obvious :)

While Tanya less than a day from the birth, but she has gave great impressions of joy to her parents — me and my wife Kate aka LLLike. And how many more to come!

A few years later Tanya Mirzayanovа will read this post, and I'll tell her: "Look Tanya, how many good and intelligent people from different corners of the Earth congratulate you!" :)

Happy and contented,
MikeMirzayanov

UPD: Thank you all for your congratulations! I did not expect to read so many warm and wonderful comments. A number of pluses proves the eternal truth: "Children are flowers of life". Thank you!

Hello!

Today is November 7th. And this, as you probably know, is a very special day for many ex-USSR citizens. Many years ago on this day the Great October Socialist Revolution happened. I still remember red flags and military equipment on the avenue and the feeling of common joy and holiday. But today, in 2011, we have another revolution — the Codeforces revolution of colors and titles. Hooray!

So, over the last few months our community has grown significantly. If we count the users who have participated in the rated contests over the last 9 months at least once, at the beginning of the year they were 4330, and now — 7615. This is a great step forward! Of course, this leads to a dramatic rating inflation. Most of the ELO-like ratings have the same issue. For example, only A. Karpov had Elo chess rating of more than 2700 in 1979; however, there were as much as 15 people with such rating in 1994, and in 2009 they were 33. In 2001 there were less than 10 red players on TopCoder; in 2005 they were about a hundred and now — more than 250.

A similar effect occurred on Codeforces. It is particularly striking as it is accompanied by a marked audience growth. For this reason it was decided to change the color system . In addition, the record shows that not all participants liked the military ranks. Besides, they are quite far from our intellectual and sporting spirit. Today we will disband Codeforces as a military unit and introduce sport titles. We've mostly used the titles from intellectual sport games to work out the following classification:

In addition, the rating recalculating formula was slightly fixed to slow down the inflation. Now the sum of ratings will not be the constant, but is likely to be slightly falling. In fact, the changes are cosmetic and will be visible only on a series of contests.

I understand that for some of you it will be hard to say good bye to the favorite color, but let's look ahead with optimism — new victories will bring the lost color back color and help to win the proud title of a Grandmaster!

MikeMirzayanov

Hello!

Informal contest Codeforces Testing Round #2 is scheduled on 10/29/2011 01:00PM (UTC). We will test the latest innovations on Codeforces that they do not affect the contests. If not, we will fix it quickly :) So, this round will take place "as is", no warranty about it.

Problems for the round may be famous to someone, but I'll try to make them such not for any of you. It will be about 4 problems, as quite simple and something more tricky.

I say thanks in advance to all those who will come and test the system. Thank you!

The contest moved to start on 10/29/2011 01:00PM (UTC) (it has been announced to start on other time, be careful).

It will be unrated round.

Thank you all for your help. I think it turned out pretty fun for you and useful for us!

Hello!

Today, October 23 (Sunday) at 08:00 (UTC) will begin online contest based on recently completed ACM-ICPC NEERC Southern Subregional Programming Contest 2011. Two days ago a competition was held in Saratov (hosted by Saratov State University), but today you can participate in it informally. Onsite participants will in the standings, to give you an oppotunity to compare your results with onsite teams. The statements will be available as a PDF-file and in HTML. To participate, go to the site http://acm.sgu.ru.

After the contest, you may discuss here the problems. I hope you'll like them.

Chairman of the Jury,
MikeMirzayanov

Hello!

Yesterday I got to the Hollywood (not in California, but in Florida). Then I came out from airport, I felt hot, humid air. Not forgotten feeling from the ACM-ICPC finals tried to fool my brain, that I was not leaving Florida.

I was flying with Misha Kever (which the handle here?). Artem Rakhov (RAD) appeared when I was asleep. It seems that he has arrived together with Sergey Rogulenko(SergeyRogulenko).

It turned out that the rainy season is not over. So here “cloudy, possible rain." I did not like the ocean — very warm, quite without the waves, it is necessary to overcome large distance to swim on depth.

By the way, I’m in the room #1760. It will be good to see in comments rooms of other finalists.

As they say, to be continued ...

Hi!

I regret to inform you that the Codeforces Beta Round #88 is rescheduled for September, 23 (Friday), 15:00 (UTC). The main reason lies in me — because of trip to TopCoder Open, I must leave Saratov, and I can't make the round being in a train, in the middle ofendless Russian steppes.

I hope that the new schedule will be comfortable for some of you, and other will try to adjust plans to the schedule.

Hi everybody!

Okay, we've got good news and bad news. What do I start with? Okay, let's start with the bad news to finish more optimistically.

As I was removing the results of some recent vandalism acts (i.e. contribution cheating), I also accidentally removed the results of all your votes :(. I am really sorry and this situation is very unpleasant to me too. We've managed to restore most votes from the backups but the last month has been lost for good. Let me offer my deepest apologies for the incident. I've manually returned the rating to the main page posts, but the votes for other posts and commentaries of the last months have dropped to zero. To soothe the damage somehow, I can stress the popular notion that we are all here to solve problems and discuss the programming and the contribution is not nearly as important.

Yet every cloud has a silver lining: the incident has already inspired me to fix the daily backup system which had been malfunctioning ever since the infrastructure moved to the new server. By the way, the back-ups transfer every night to the VK data centre (our special thanks toVK) — so I'm not that afraid even of a nuclear bomb hitting the Saratov SU server room.

Besides, I guess it's high time we put effort into fight with spammers, bots and other vandals. The directions to work in have been voiced by the community members — we can limit the unrated members' actions, introduce captcha here and there, maybe there'll be something else.

Let me offer apologies once more, I hope I'll never ever re-live the emotions I experienced today. Just in case let me remind you that there is a beta letter in the logo not without a reason.

Now then, let me proudly present to you some small innovations.

• Direct links to the submission. They are of the following form http://mirror.codeforces.com/contest/contestId/submission/submissionId and are available though a submission pop-up window (cluck the # symbol in the title).
• We've introduced special Codeforces tags in posts/comments.

All tags possess the form [[tagName:param1,param2,...,paramN]], the square brackets are replaced by round ones in the examples below so that our innovations don't process the examples. Of course, when you use tags you should use square brackets. Now then, the details about the possible tags are as follows.

• Write ((user:handle)) to add a link to the user profile. The link gets bound to the current date so that the user has the color and rank valid at the moment of publication. For example, you can write the following in a comment "((user:Petr)) is number one in the Codeforces rating".
• Use ((contest:contestId)) to add a link to a contest. Such tag is displayed as a contest name but alternative contest is also acceptable. Try writing "I took part in the contest ((contest:115))" and also "I took part in the ((contest:115, contest))".
• A link to contest results is pasted similarly: "the results are available via link ((standings:115))" and "the results are available via the ((standings:115,link))".
• You can paste a link to problem (via the problem's code). E.g., "How to solve problem ((problem:115B))" or "how to solve ((problem:115B, this problem))".
• And at last, you can past a direct link to submission. The examples are "here's the submission link: ((submission:700734))" or "here's ((submission:700734, the problem submission link))".

Of course one should copy carefully when writing a tag as the copied HTML styles can interfere with the tag's contest. And finally, let us demonstrate some examples in action:

• Petr is number one in Codeforces rating
• Thanks to dolphinigle for Codeforces Beta Round 87 (Div. 1 Only) and Codeforces Beta Round 87 (Div. 2 Only)
• The results of the recent contest are available via this link
• 704386 — a short solution to the problem 115B - Lawnmower

That's the news for today,
MikeMirzayanov

As some of you have already noticed, we are introducing the innovation &mdash a virtual contest system. I guess this term was invented as far back as in 2002, as we were working on the site http://acm.sgu.ru/. Besides we were the first ones to come up with and carry out the interesting idea: enable the users to run the past contests in a special mode that would imitate a real competition. It feels just like a real contest with real contestants competing alongside with the participant who writes a virtual contest.

The idea was a success and it was picked up by some online judges. Although frankly speaking, those ideas haven't been carried out by the many.

And now it's time to introduce the virtual contest system to Codeforces! Of course, the original Codeforces rules aren't easily converted to virtual form. That's why all past Codeforces contests will be available as virtual contests by ACM-ICPC rules. In light of oncoming ACM-ICPC subregional and regional contests it can be regarded as yet another opportunity to train.

Virtual contests are available to individuals as well as to teams. If you participate as a team, please make sure that the registered team represents all your team members and nobody else. If it is not the case, change it. So far there's only one contest available for alpha-testing: it's Codeforces Beta Round #76 (Div. 2 Only), but you won't have to wait much - soon all contests will be available in this mode. Now all the past contests are available as virtual contests.

When you take part in virtual contests please follow those simple rules:

• don't participate if you've already seen the tasks;
• don't participate if you only want to commit one problem or if you don't want/can't participate in the whole contest;
• during the contest don't read tutorials, don't use somebody else's code, don't talk to other people;
• try to make it an efficient and enjoyable training!

I expect some of you to write the offered contest virtually and share your impressions. For example, JKeeJ1e30 has already participated!

I hope you like the new opportunities. We'll add something, too, to give the system final flourish, but in any way we're waiting for your commentaries rich in interesting ideas and suggestions.