Hello everyone!

Codeforces Round #223 will take place on Sunday, January 12th at 19:30 MSK. This is my tenth Codeforces round and I hope not the last.

I'd like to thank Gerald 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.

This is the first round this year. Incidentally, the first round last year for both divisions was also mine (by statistics +1/-1 is was the coolest of rounds that I gave). I hope that this time the problems will be even more interesting for you. Will it? Will find it out after the round :)

Gl & hf ! :)

Problem point values will be standart for both divisions.

Hurry! Only until the 10th of January, you can change your handle! Note that it will be possible to roll back the changes or change the handle again only after a year.

Talking about handles I always reminisce the following story. Once a user wrote me the message: "Please change my handle from I_love_Valya to I_love_Sveta, as I no longer love Valya ..."

Happy New Year!

Hello! Do you feel the breath of New Year?

The clock shows a day before New Year, so it is time to sum up the past. I do not have speech-writers for words in the style of "what recently seemed almost impossible, it becomes a fact of life" so I'll be short. Thank you all! Your unfading interest and constant help inspire Codeforces team for new achievements! Brilliant writers, invisible soldiers: testers, tireless and greedy for knowledge participants — all of you help Codeforces do better!

I've dug into the records and made a partial list of the most notable major improvements of 2013. Some large improvements of our infrastructure are not in the list, as the community can not see them directly.

• A simple way to add contest from Polygon to Codeforces::Gym.
• Drafts embedded in text form fields in Codeforces and Polygon.
• Multiple interface improvements in the contest area.
• Many improvements of Testlib.
• Notably improved performance of Polygon on large manual tests.
• Repeatedly updated compiler versions to the nearly latest.
• Supported languages: MS C#, Python 3, Go, JavaScript V8.
• Updated Codeforces testing servers.
• Polygon supported HTTPS.
• Organized the first season of weekly Codeforces trainings 12 episodes.
• Supported organizations in the profile and rating of organizations.
• Added numerous contests to Codeforces::Gym. Probably the most valuable — a large number of Andrew Stankevich Сontests.
• Implemented checker and validator tests in Polygon.
• Implemented macro language support in test scripts in Polygon.
• Groups on Codeforces have appeared, they can contain contests and blogs.
• Introduced Mashup Contests — special contests for personal and group training, can be easily composed by problems from rounds or from Polygon.

In addition, in 2013 we not only hosted 64 classical Codeforces rounds, but hosted some tournaments:

• Croc Champ 2013
• MemSQL start[c]up
• ABBYY Cup 3.0

Also we took a role of ACM-ICPC 2013 World Finals Press Partner!

And as the detective story can not be without a chase, and the annual report can be do without the fun pictures. Here is a series of images showing the growth of Codeforces:

Good day)

Welcome to the last Codeforces round in this year Good Bye 2013. This round will be unusual because it will be common for participants of both divisions.

The problems were prepared by authors Gerald Agapov (Gerald) and Svechnikov Artur (ikar). Pavel Kholkin (HolkinPV) and Vitaly Aksenov (Aksenov239) also help us to prepare the problems. Traditionally thanks to Michael Mirzayanov (MikeMirzayanov) for Codeforces and Polygon systems and Mary Belova (Delinur) for translating the problems.

UPD: Score distribution is similar to standard — 500-1000-1500-2000-2500-3000-3500

UPD2: Thanks to all participants, we hope everyone enjoyed prepared tasks. Problem analysis.

UPD3: Congratulations to the winners of the last round in this year. Rating will be changed in a few hours.
1. BaconLi
2. Egor
3. liympanda

We wish everyone good luck, high rating and excellent mood)

Hi all!

Authors of today's round are craus and dalex. We just couldn't miss the round with such a beautiful number, so at 19.30 MSK you will solve problems which were invented by Pavel and prepared by me.

We thank Gerald and Delinur for their help in contest preparation and MikeMirzayanov for creating Codeforces.

Scoring system and score distribution will be published when the round starts. Anyway this information makes no sense unless the round begins.

We wish you accepted solutions and successful hacks!

UPD. Contest is over, congratulations to the winners!

Div. 1:
1. Petr
2. tourist
3. Egor

Div. 2:
1. k3e18
2. tongcx1988
3. LeMieux

UPD. 2 Problem analysis is published.

Hello, Codeforces.

UPD: Mashup feature is disabled until the end of the round. This is temporary and won't happen in the future.

Today we want to present you with our latest feature: mashup contests.

Hi, Codeforces Round #221 will take place on December 24th at 18:00 MSK for both divisions.

Problem setters are whd, oGhost and boleyn.su. This is our first Codeforces Round, and we hope it will be a good one.

We'd like to thank Gerald and alpc104 for helping us prepare this round, and MikeMirzayanov for bringing all of us a place to compete and communicate with others.

The score distribution will be announced before the contest starts.

UPD1: The score distribution is 500-1000-1500-2000-2500 for both divisions.

UPD2:

Congratulations to winnners and Merry Christmas to ones who celebrate it today!

Div 1:

1.Touma_Kazusa

2.al13n

3.rng_58

4.hmspmy077

5.uwi

Div 2:

1.bohuss

2.Tyg3R

3.xhsong

4.adamant

5.Kira96

I've found some time to support JavaScript, which is so popular now. I chose V8 as the most developed implementation of JavaScript.

With the help of a tambourine and a liter of cola I successfully compiled it on Windows. Funny, I was ready to implement workaround to support reading from stdin in JavaScript, but d8 already supports it! Just use readline() to read line from the input.

Here is an example of A+B:

var line = readline().split(' ')
print(parseInt(line[0]) + parseInt(line[1]))

Interesting fact, that if there is no line-break (\r\n) at the end of line, then readline() returns undefined. So it is one more reason for good rule: each line should end with eoln.

As a tiny research I've implemented HeapSort on C++, Java and JavaScript. I have an opinion that all dynamic typed languages are very slow. But...

I've implemented HeapSort on 10⁷ elements from 0 to 9999999. I think it is good benchmark to show how fast can be your code if you write like in Pascal or pure C. The result have surprised me:

JavaScript shows very good performance! I understand that such kind of code is very good for optimization and jit-compilation, but I'm impressed. By the way, Java with its optimized JIT is not as good as it can be.

Actually, I posted the codes in github. You may implement the same algorithm on your favorite language. Here are links to current implementations:

• С++
• Java
• JavaScript
• Pascal
• Python 2
• Python 3
• Ruby
• Scala
• Go
• D
• C#

You may post links to pastebin in comments or give submission id. Better to do a pull request.

If you are planning to write implementation, please write it neat and tidy. Write it as closer to the C++, Java and JavaScript as possible.

UPD 1. With the help of alexei-zayakin, Pascal has been added.

UPD 2. With the help of gchebanov Wizmann and juancate I've added Python 2, Python 3, Ruby, Scala, Go.

UPD 3. Here is V8 (Windows binaries).

UPD 4. I've updated some compilers and the benchmark results.

UPD 5. Added D. Thanks Gassa.

UPD 6. Added C#. Thanks gmogelashvili.

Hi! Soon Codeforces Round #220 (Div. 2) will take place, i am the author, Dmytro Berezin. This is my third round and Sereja still hopes, that this is the last :)

Everything changed since last round. Dima and Inna have thought about their behavior and asked Sereja to excuse them. They are good friends now. You should make the family happiness even stronger!

Thanks to Gerald Agapov (Gerald) for the help in round preparation, Maria Belova (Delinur) for tasks translations, Mike Mirzayanov (MikeMirzayanov) for perfect system, and Sergii Nagin (Sereja) for his agreement (not to post here another photo) to help in testing.

Points distribution will be. 500-1000-1500-2000-2500. Here we go :)

Hello, Codeforces.

Today group functionality was updated and extended:

Here is a list of changes:

• Personal blog entries now can be attached to the group blog.

• New blog entries can be written directly to the group blog. Such entries won’t be displayed in recent actions and votes for it or for it’s comments will not affect contribution.

• Only managers can write or attach entries to the group blog. Entries can be read by and commented by all group members.

• New group role was added. Now there are three group member types: spectator, participant and manager. Spectator is a group member, which can not register to the group contest and is not displayed in group standings. But spectator can see the standings, see the problems, read and comment group blog. For example, if you want someone to see the trainings of the group, but not to participate, you can invite the user as spectator.

• Spectator registration policy can have same values as participant registration policy. Spectator registration policy can not be more strict that participant’s one. By default it is set to be the same as the participant registration policy.

• Also, there is an additional registration policy for spectators – automatic registration. It means that anonymous and non-member users will be considered spectators. They will not be displayed in group members table. For example, if you want to organize the championship of your university, you can create a group, invite only official participants of the contest as group participants and set spectator registration policy to automatic. So only official participants will be able to register to the contest and take part in it, but standings and problems will be open to public.

• There were changes in the security policy of the group web pages. To access a group web page, user must be a group member. To all anonymous or non-member users to see the web pages of your group, you must set spectator registration policy to automatic.

With best regards, Ivan.