The mystery of creating rounds unveiled by author of the 4 of them!
The guide for preparing the round without horror-fiction and pastorals!

Thanks for RodionGork, who push me to writing this post and thanks for hball1st, who push RodionGork to pushing me to writing this post.

Also, many thanks to RodionGork for the translation of this post to English.

1. Inventing problems

It's hard to advise anything on this point. There's no some standard way of creating problems — and if one have existed we'll have only "complicated algorithmic exercises" instead of "problems". People who participated in Russian Code Cup do know well the tasks of that sort.

To cook good and interesting problem there should be some idea! which came to your mind (and later to minds of participants of the contest). Even the simplest problems of A level for the Div2 should have some idea.

So here is the warning: creative way of thinking is trained from the childhood — and since so, not all people are equally good in inventing problems. Alas!

A coder can apply his breathtaking coding skills not only in different search engines but also in the mobile game industry. It is an option in Russia. If you do not believe — check this out: ZeptoLab company that created the world famous Cut the Rope game offers you the opportunity to see this for yourself. And yes, we are in Moscow.

It's not a secret that those who strive to achieve top coding skills — work hard, including work on his self-education. Here in ZeptoLab we aim to create the area that strongly encourages self-development. Specifically, we have recently purchased a company library with everything necessary to get new knowledge, an improvised reading room with sofas and armchairs.

We also conduct developer's contest inside the company so that our ZeptoCoders could solve non-trivial problems and impress each other with zeroes and ones. The winners get glory, valuable gifts and name-encrusted weapon (it's a joke, it’s not weapon)

We have recently opened our own algorithmic school here in ZebtoLab and the teacher is no other than the creator and the head of the whole wide Codeforces, Mike Mirzayanov! He is well-known among developers: Mike has trained a team that became the world champion in programming, so it's not hard to imagine the opportunities opened for ZeptoLab developers and the whole company. It's the first time that Mike teaches in such format, there are hardly any more examples of such corporate education systems in Russia and throughout the world.

Algorithms play an important role for us as the requirements for developers are quite tough: ideally, the application should output 60 frames per second on the target gadget. All game logic calculations should be very quick and preferably, with simple and not amortized complexity. Besides, we can afford a fine pre-processing to transport some calculations to the stage at which resources for the game are prepared. Understanding this facts, alongside with many more is the key to the quick gameplay. That is why we support the algorithmist's movement.

It's the first time when Zeptolab holds an algorithmic development contest based on Codeforces. Ingenious problems, fierce developer rivalry and cool prizes are waiting for you:

• 1st prize: Ipad Air, plush Om Nom, the championship T-shirt
• 2nd-3rd prize: Ipad Mini, plush Om Nom, the championship T-shirt
• 4-th-30-th prize: plush Om Nom, the championship T-shirt
• 31st-50th prize: the championship T-shirt

And just for some suspense, we add another prize:

We will randomly give the IPad Mini Retina to the person who makes it to the top 50 list of the contest champion. The IPad winner will be chosen like this: we sum up the times of all successful attempts of three top winners (in seconds starting from the start of the contest) and take a row with number s % 47 + 4, where s is the resulting sum. Being true coders. If the resulting line divides the place, then the priority goes to the earlier person to submit his last solved problem.

Besides, the person who shows good results in the contest will have the opportunity to apply for a job in our company by a simplified scheme. If you'd be interested to try working in the ZeptoLab team, tick the corresponding square at the registration.

You can find out more about what working with us is like at http://zeptoteam.ru/.

The championship will be conducted in a single round. The contest will go by the Codeforces rules. The round will be rated and both divisions can participate.

The date and time of the contest is: June 13, 2014, 15:30PM — 18PM (UTC).

The problem scores are: 1000-1000-1500-2500-2500-3000.

The contest is over! Thanks for all the participants! We hope you like the problems and the contest! Our special congratulations to the winners:

• The 1st place — KAN (Nikolay Kalinin, Russia, Nizhniy Novgorod) — iPad Air
• The 2nd place — winger (Vladislav Isenbaev, USA, Facebook) — iPad Mini
• The 3rd place — tourist (Gennady Korotkevich, Russia, Saint Peterburg, ITMO) — iPad Mini

All the participants on the places 1-30 will receive presents: plush Om Nom and the championship T-shirt. All the participants on the places 31-50 will receive championship T-shirt!

Additional prize will be received to the the 21st place winner: package.zaic (Vadim Zaycev, Russia, Novosibirsk, NSU).

Hello!

Soon (on June 8 at 19:30 MSK) you are lucky to participate in Codeforces Round for Div. 2 participants. Traditionally, Div. 1 participants can take part out of the competition.

Problems have been prepared by: Gridnev Vitaly (gridnevvvit) and Danil Sagunov (danilka.pro).

We want to thank Gerald for help in preparation of this round, Delinur for translation of statements and MikeMirzayanov for marvelous Codeforces and Polygon systems.

Scoring will be next 500 — 1000 — 1500 — 2000 — 2500.

Contest finished, congratulations to winners!

1. kuangbin10
2. ToumaKazusa
3. qiaoranpenxiang
4. rotoZOOM
5. umczca195

Editorials will be there

Good Luck!

Will begin today, at 21:00 MSK. All paricipants, advanced to the elimination stage, are welcome to participate through the link. This round will be 100 minutes long and will be scored using Grand-Prix 30 system. First place in Round 1 gave pperm86 100 score points and invitation to the final round in Berlin! Who will reserve his place among the finalists today?

Good luck!

P.S. In case of infinite redirect loop, please, clean browser cookies or use an incognito mode

Hi everyone,

Codeforces round #251 for division 2 participants will start at June 4, Wednesday, 19:30 MSK (usual time). Traditionally we invite Div.1 participants to take part out of the competition.

The round was prepared by me (PraveenDhinwa). This is my first codeforces round. I have tried my best to make the problem statements as clear as possible. I hope that everyone will enjoy the round.

Special thanks to Gerald(Gerald), for his extensive help in problem ideas verification, problem testing, without his help the contest would not have seen the day. English translation is done by me with a lot of help from Gerald Agapov(Gerald). Problems are translated in Russian by Maria Belova(Delinur).

Many thanks to Pratik Moona(pratikmoona), Varun Nitish(JuanMata) for providing their help in testing of round. Their help is greatly appreciated :)

Many thanks to Devendra Agrawal(devu)Utkarsh Lath(utkarshl) to helping me in verifying the ideas of problem statements.

Many thanks to Mike Mirzayanov(MikeMirzayanov) for creating this wonderful platform :)

The contest problems are dedicated to my dear friend Devu (devu), He once proposed problem titled "Churu, the thief". Churu is my nick-name. So it is now time to take some revenge in a funny way :P

Score distribution for the contest is standard: 500-1000-1500-2000-2500.

I have a good news for you too. Tutorial of the contest will be available as soon as the contest ends :).

I wish all the participants good luck, high rating and lot of hacks :) Don't miss the round.

UPD Thank you everyone for participating. I hope that you have enjoyed the round, Thank you all !!

Editorial

We've introduced API and now we want to test the system before Round 251.

I invite you to take part in Testing Round 10. It starts on usual time, June 3rd. It will be unofficial unrated round.

I tried to pick up the problem to make the round interesting for many of you. Pretests are unusually weak to trigger more hack.

If you see any unexpected behavior or bugs, please inform us via comments.\

Thanks.

Hello, Codeforces!

Today we want to introduce Codeforces API. With it you now can access some of Codeforces data in machine-readable JSON format.

API has a detailed manual, which is supported to contain only actual information. Every method has an example URL. You can use it to see the example response and to experiment with different parameters.

By default, any API request will be anonymous and will have access only to public data. To make a request on behalf of some user, a user must create an API-key at /settings/api and read the bottom part of the manual at /apiHelp.

For now, all methods are read-only. Write-methods like "submit a solution" are coming soon.

We are open to suggestions and requests for new API-methods. Especially from respected members of contest programming community.

With best regards, Ivan.

Happy Children's Day everyone. What should you do to celebrate the special holiday?

Of course, another Codeforces Round is your best choice!

There is a child who is our friend. Now he has faced a lot of algorithm problem, could you please help him?

We invite you to participate in Codeforces Round #250, which will take place at 17:00 MSK on 6.1 — Children's Day. This round will be held in both divisions.

Note that the starting time of this round is quite unusual.Why? Because it's yet another CF Round held by Chinese! We prepared many interesting problems for you.

Are you getting excited? Don't miss this round!

The problems were prepared by delayyy, Picks and me. This is our first Codeforces round~~~~.

Many thanks to Gerald, who gave us enormous help during the preparations for this round; to ftiasch, Kissshot and jqdai0815, who are the testers of this round; and to MikeMirzayanov, who created such a wonderful platform.

In Div. 1, scores for each problem will be 500-1000-1500-2000-3000.

In Div. 2, scores for each problem will be 500-1500-1500-2000-2500.

Look! Your high rating is waiting for you! What are you waiting for?

Just participate in this contest and write code fast and nicely, and you will take the high rating home!

Good luck and have fun!

UPD: The contest is over! Congratulations to winners!

Top 5 of Div. 1:

1. Alex_2oo8

2. Petr

3. Dmitry_Egorov

4. TankEngineer

5. al13n

Top 5 of Div. 2:

1. tohdon

2. KFDong

3. function348

4. 104325EA

5. Boyuede1

Unfortunately, no one has solved the problem E in both divisions. What a sad story....

Editorial for the round will be added soon.

UPD2: Editorial for the round can be found here: Editorial