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!

Hello everyone!

We invite you to participate in a new team programming contest Asseco Programming Marathon24 Gdynia 2013. In the contest teams of three can participate. There is no limit concerning the age or education of contestants. Also there is no limit in equipment, programming languages or materials you can use during the contest.

The contest consists of two stages. If you have participated in Challenge24, you should be more or less familiar with the format.

The first stage are qualifications, which will start on 19th October 2013 at 9:00 CEST and will last for 5 hours. There will be 5 algorithmic problems, to which 10 test cases will be provided. You only submit outputs to the tests and you get immediate feedback on your score. Some problems will have only one answer, and some will be optimization ones.

No more than 30 teams with the highest scores will qualify for finals. They will take place in Pomeranian Science and Technology Park in the city of Gdynia in Poland. Finals will begin on 30th November 2013 at 11:00 CET and will last for 24 hours. There will be 3 problems, which will require you to write a program communicating with the contest server through the TCP/IP protocol. A sample problem could be controlling a team of units which compete with other teams on a virtual arena. On the contest site you will be provided with table, chairs, lighting, one power socket and one network plug. Any other equipment has to be brought by you. Organizer will provide accommodation before finals (Friday/Saturday) for every participant of the finals. Organizer does not pay for or provide transportation to Gdynia.

For three teams with the highest scores in finals there are prizes amounting to over 30 000 PLN in cash.

The problems will be prepared by Tomasz Idziaszek monsoon and Wojtek Nadara Swistakk. Even if you don't have a team of three, you are still able to solve problems for fun during qualifications. Just register yourself and create a single-member team.

For more information or sample problems visit our site: www.marathon24.com. Keep in mind that the registration closes on 17th October 2013.

Good luck and have fun!

Hello everyone!

Codeforces Round #204 will take place on Friday, October 4th at 19:30 MSK. This is my eights Codeforces round and I hope not the last.

I'd like to thank Gerald, yvasyliv, Cenadar and Zlobober for helping me to prepare the round. Special thanks to Delinur for translation of all problem statements into English.

I strongly recommend you to read ALL the problems.

Problem point values for the first division: 1000-1000-1500-2000-2000.
Problem point values for the second division: standart.

Tutorial.

Gl & hf ! :)

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!

Hello!

Soon (on October 1 at 19:30 MSK) you are lucky to participate in Codeforces Round #203 for Div. 2 participants. Traditionally, Div. 1 participants can take part out of the competition.

Problems have been prepared by me. I want to thank Gerald Agapov (Gerald) for help in preparation of this round, Ilya Los (IlyaLos) for testing of problems, Alexander Ignatyev (aiMR) for testing of problems and for idea of one of the problems, Michael Mirzayanov (MikeMirzayanov) for marvelous Codeforces and Polygon systems, Mary Belova (Delinur) for translation of statements.

Good luck!

UPD:Scoring will be dynamic. Problems are sorted by increasing order of difficulty.

UPD: Congratulations to winners:

1. fanhqme
2. FAU.COACH
3. Witalia
4. sokian

UPD: Editorial

Good night/dawn/morning/day/dusk/evening/night, Codeforces!

Today I am glad to present you the latest features of the Polygon — the system for creation and preparation of programming problems and contests. All Codeforces Rounds are made using Polygon.

New features are concentrated around test script.

Part one. Test autonumeration

The first new feature allows you to automatically numerate tests.

Instead of this

gen_n 5 10 1 > 57
gen_n 5 10 2 > 58
gen_n 5 10 3 > 59
gen_n 5 10 4 > 60
gen_n 5 10 5 > 61

you can now write this

gen_n 5 10 1 > $
gen_n 5 10 2 > $
gen_n 5 10 3 > $
gen_n 5 10 4 > $
gen_n 5 10 5 > $

Dollar sign, used to mark autonumeration, stands for the first unused test index. So, for example:

gen 1 > $
gen 2 > $
gen 4 > $
gen 5 > $
gen 3 > 3

will be translated to

gen 1 > 1
gen 2 > 2
gen 3 > 3
gen 4 > 4
gen 5 > 5

But don't you think, that dollars will be replace with actual numbers upon saving the script. It would be too easy and boring. Of course, they stay. If you enter the script from example above and save it, you will see this:

gen 1 > $
gen 2 > $
gen 3 > 3
gen 4 > $
gen 5 > $

If you delete any test, all dollar tests will be renumerated instantly and they will still be dollars instead of exact nunbers.

Also, did you now, that you can drag and drop tests to renumerate them? For example to move 40th test to the 7th position? This feature is very old, but it is rarelly noticed, so I decided to remind you about it. Dollar tests are also drugable.

But there is always a fly in the ointment. We decied not to support dollars for generators, which generate multiple tests. They have syntax like this

gen > {5-10,12,15}

So generator must produce 7 tests and put the to files 05, 06, ..., 10, 12, 15. So if we made them dollars and delete test number 1, we will get {4-9,11,14} instead of {5-10,12,15}.But the generator is not changed and still produce files 05, 06, etc. To avoid such problems, generators with file output does not support dollars.

Part two. Scripts for generating scripts

Now you can write script using Freemarker Template Engine, that will be executed inside the Polygon and the result will be used as test scritp. So for example instead of this

gen 10 1 1 > $
gen 10 1 2 > $
gen 10 1 3 > $
gen 100 4 1 > $
gen 100 4 2 > $
gen 100 4 3 > $
gen 1000 9 1 > $
gen 1000 9 2 > $
gen 1000 9 3 > $
gen 10000 16 1 > $
gen 10000 16 2 > $
gen 10000 16 3 > $

we can just write this

<#assign n = 1>
<#list 1..4 as pow>
    <#assign n = n * 10/>
    <#list 1..3 as i>
        gen ${n} ${pow * pow} ${i} > $
    </#list>
</#list>

You can find a brief tutorial about Freemarker at https://polygon.codeforces.com/docs/freemarker-manual. To find more details about the language you can read the official documentation.

But, script must be always consistent with the test table. It adds some limitation to the use of Freemarker.

• It is impossible to delete, edit or move script test using web-interface. To do it, you must edit the script directly.

• It is necessary to use dollars instead of indices. This limitation allow us to move manual test to any possition without changing the script.

• Dollars are not supported by multiple test generators, so it is impossible to use them inside Freemarker script. But, in my opinion, if you already wrote program, that generates all tests, why would you need Freemarker : )

As you will see, there are two new buttons near Save Script: Preview Script and Run Script.

Preview Script shows you the final result — which test will get which generator line.
Run Script replaces your Freemarker script with old-style script, in other words, with the sequence of generator lines. You can use this button, if you do not need Freemarker any more? but could use some of the locked features. Please note, that this button only replaces the script in the text field. You need to save it by pressing Save Script button.

That is all for now. I hope new features will make it easier for you to prepare problems for Codeforces Rounds and other contests.

With best regards, Ivan.

Hello, Codeforces!

Codeforces Round #202 will take place today, September 27 at 19:30 MSK.

The idea behind the round was born when my friends and I were interning at Facebook this summer. This round probably has the highest number of authors for a Codeforces round to date. The authors of the problems are Azizkhan Almakhan azizkhan, Michael Kolupaev al13n, Filip Hlasek fhlasek, Ivan Mandura budabudimir and myself, Igor Demidov caustique.

Maxim Korystov dark_ai, Alexander Fedulin Jughead and Ibragim Ismailov ibra, Vladimir Chalyshev cmd and Sergey Sklyanichenko Sklyack helped us with preparation of the round.

The ideas behind the 2 problems were inspired by Anton Ermilov ant.ermilov and Dmitry Krasnov navi-spb.

Testers of the round are Alexey Safronov yarrr and Alexey Shmelev ashmelev.

I would also like to thank Gerald Agapov Gerald for his help in preparing the contest.

I hope you find problems interesting and diverse. I'm sure that everyone will find the problem to their liking.

Scores are as usual 500-1000-1500-2000-2500.

Good luck and have fun!

Congratulations to the winners!

Div. 1

1. ilyakor
2. rng_58
3. EnumerativeCombinatorics
4. ftiasch
5. phtniit
6. SillyHook06
7. niyaznigmatul

Div. 2

1. zhk
2. love_kd
3. alex_k
4. arpit11293

Attention! Editorial for all problems is available!

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!

Hello everyone!

Codeforces Round #201 is scheduled to take place at Friday, Sep. 20th at 19:30 MSK(23:30 CST)

Setters are: CMHJT and me.

Testers are: error202, havaliza and tourist.

Thanks to MinakoKojima for her help in rewrite the statements into codeforces style, Delinur for her help in translating the problems to Russian, and MikeMirzayanov, who has designed such a powerful platform.

Special thanks to tourist and Gerald in giving advise about the problems so we could put them in a more proper order.

500 — 1000 — 1500 — 2000 — 2500.

We are going to use standard score distribution in both divisions. The problems are not so hard, but you need more thinking rather than coding.

Good luck!

UPD1: Congratulations to the top 5 winners in each division!

DivI

1.cgy4ever

2.rng_58

3.PavelKunyavskiy

4.Egor

5.liympanda

DivII

1.Thrax

2.renannewbie

3.socksister01

4.SJTU_WengJian

5.cat_leopard

UPD2: the editorial is published here