Hi!

We're glad to invite you all to participate in Codeforces Round #360(Div. 1 and Div. 2) which will take place on Wednesday, 29 June, 20:05 Moscow time. Check it in your timezone!

The problems are designed by Man (Parsa Abdollahi) and me. It's our first Codeforces round and we hope you enjoy competing it as much as we enjoyed preparing it! (^◡^)

Our special thank goes to JeBeK (Peyman Jabbarzade) who helped us a lot in preparing and testing the round. Many thanks to GlebsHP (Gleb Evstropov) for his help in preparing the contest, and MikeMirzayanov (Mike Mirzayanov) for great platforms Polygon and Codeforces. We also want to thank Zlobober (Max Akhmedov) for testing our round.

We wish (and expect!) you all many Accepted solutions! ( ﾟ▽ﾟ)/

UPD: Problems are going to be about Pari and Arya.

UPD2 Congratulations to the winners!

Div. 1:

1. jqdai0815
2. tourist
3. Egor
4. xyz111
5. subscriber
6. riadwaw
7. ainta
8. jcvb
9. Um_nik
10. Shik

Div. 2:

1. Julek
2. polygonia
3. Snipx
4. I_love_littlechild
5. AminAnvari
6. Shayan
7. yashkumar18
8. Archies
9. Clone3
10. lature

Editorial + some challenges will be published soon.

UPD3: The editorial is out!

Ladies and Gentlemen!

The Codeforces round #359 for both divisions will happen on 23 June at 7:35 PM MSK. We have been choosing and solving problems for a long time and we hope that they will seem quite interesting.

All of the problems were created under guidance of Endagorion (Mikhail Tikhomirov) by Moscow high school graduates: cdkrot (Dmitry Sayutin), ch_egor (Egor Chunaev), themikemikovi4 (Mikhail Sorokin) and me. It is our second Codeforces Div.1 + Div.2 round.

Thanks to coordinator GlebsHP (Gleb Evstropov) for help with preparing problems and to MikeMirzayanov (Mikhail Mirzayanov) for excellent systems Polygon and Codeforces. Also, the round is possible only because of Endagorion's help.

Participants will be given five problems in both divisions. The scoring distribution will be announced later.

Good luck to all!

UPD: All statements are based on the fairy tale "The Snow Queen" by H. C. Andersen.

UPD2: The scoring distribution:

Div. 1: 500-1250-1250-2000-2500

Div. 2: 500-1000-1500-2250-2250

UPD3: Congratulations to the winners!

Div. 1:

1. Petr

2. jcvb

3. dotorya

4. ainta

5. matthew99

6. Errichto

7. yosupo

8. Myungwoo

9. RAVEman

10. zemen

Div. 2:

1. aasddf

2. jupanul

3. ItsLastDay

4. dacin21

5. RedRiver

6. --d

7. heracle

8. abcdeedcba

9. IgorKoval

10. 131131yhx

UPD4:

Cheating detection may affect the ratings a little.

UPD5:

The editorial can be found here.

The Codeforces Marathon Round 1 is over (results comment). As the final solutions are being tested, I think many participants will want to share ideas and learn alternative approaches. I'll start with the ideas I tried myself, both successful and not; as I've seen in the submissions, the contestants have more ideas, but I hope they will share themselves. For each of the solutions below, the numbers in square brackets are minimum, mean and maximum score when running on 1000 tests locally. I have to note in advance that the constants and technicalities in the solutions are not considered optimal: the score just shows approximate relation between ideas and may often be improved a bit.

Hello!

Let us remind you that Russian Code Cup 2016 Elimination Round will take place on June 19, 2016 at 14-00 Moscow time. Top 200 from each qualification round can take part in Elimination round, 200 best coders in Elimination round will get branded championship t-shirt, and top 50 will advance to the Final Round that will take place in September. There are money prizes to grab in the Final Round.

Good luck everyone and see you at http://russiancodecup.ru !

There has been talk about this already, but in case anyone missed it:

The 2016 edition of Internet Problem Solving Contest is going to take place today (starting time).

It's a 5-hour contest for teams of up to 3 people, but there's also an individual division, so feel free to participate even if you can't find yourself a team at this point.

There's going to be an ACM-like number of problems (12+), ranging from classic algorithmic problems to quite unusual ones. Most problems have an easy subproblem worth 1 point and a hard one worth 2 points (think CodeJam); ties are broken using ACM rules (sum of times).

The practice session is over. The contest is over!

Read the rules or my previous blogposts about this for more info.

Belated, yet necessary warning!

Since this is a 5-hour contest where you can execute codes locally, some inputs will be YUGE (gigabytes). Accordingly, they will have fairly high system requirements. Get a good computer. While the official solutions quite comfortably run on my mediocre laptop, if you write something too inefficient, you can encounter a nasty surprise, e.g. frozen system. It happened to me last year.

If an input is big, you won't have to download it; instead, there will be a generator (typically a Python script, meaning they aren't very fast). It's usually a good idea to run all generators as early as possible — as long as it doesn't slow down your computer too much, you can avoid a situation where you can't submit a problem because the contest ended before your generator.

Actually, you should just try to read as many problems as possible and determine your strategy after you can guess your chances well enough.

Some quick stats

11145 submissions
5370 successful submissions (48% success rate)
797 active teams out of 1376 (58% did not give up before even trying)
773 teams with positive score (97% of active teams)
12/13 problems solved by someone
maximum number of fully solved problems: 10/13
lowest non-zero success rate: D (D2: 20%)
highest success rate: C,F (C2,F2: 85%)

highest success rate (easy subproblems): G1 (85%)
lowest success rate (easy subproblems): J1,M1 (25%)

hard problems (<50 teams solved) sorted by difficulty:
E: 0/13
M: 2/10
J: 4/17
H: 11/17
B: 11/18
L: 16/46
K: 40/107

Hi everyone!

Codeforces Round #358 (Div. 2) will take place today on the 17th of June at 19:35 MSK.

I am the author of all the problems, and this is my first round on Codeforces. I hope you will enjoy it.

I'd like to thank Gleb GlebsHP Evstropov and Dan danilka.pro Sagunov for helping me in preparing problems, Mike MikeMirzayanov Mirzayanov for the great Codeforces and Polygon platforms.

There will be five problems and two hours for solving them. The scoring distribution will be announced later.

UPD

Scoring: 500-1000-1500-2000-3000

UPD

Editoral

UPD

Congratulations to winners!

Div.2:

1. Subway_Sandwich

2. mcdonalds

3. KentuckyFriedChicken

4. zijue

5. dacaiji

Div.1:

1. MrDindows

2. Um_nik

3. anta

4. uwi

5. Shik

The language of the round is Kotlin. Kotlin is a statically-typed programming language that runs on the Java Virtual Machine and also can be compiled to JavaScript source code. Its primary development is from a team of JetBrains programmers based in Saint Petersburg, Russia (the name comes from the Kotlin Island, near St. Petersburg).

Here is an example of the simplest program on Kotlin to print sum of two numbers:

fun main(args: Array<String>) {
    val (x, y) = readLine()!!.split(' ').map(String::toInt)
    println(x + y)
}

Here are some links to help you with Kotlin:

• https://en.wikipedia.org/wiki/Kotlin_(programming_language)
• https://kotlinlang.org/docs/reference/
• http://try.kotlinlang.org/ — be careful: reading from the console in the web-IDE is not allowed
• and Google!

You can download standalone compiler (version 1.0.1) by the link http://s.codeforces.com/files/kotlin-compiler-1.0.1.zip Also you need JRE (virtual Java machine), you can find it by the link http://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html

The password from the archives with IDEA (IDE supporting Kotlin out of the box): c8bf9dd9b91ad9ff Links to IDEA are below or you can download it from the official website

Good luck!

====

UPD: You can predownload development pack (sorry, 300MB). In fact, you can take part without it — the Custom Invocation tab will be available during the contest. Also we will publish more compact tools 30 minutes before the start.

All archives are encrypted. The password will be announced 30 minutes before the contest.

========

Surprise Language Round #8 will start on June 16, 16:00 (UTC). It will be unusual entertaining contest. Solutions on the only programming language will be allowed.

Thus, it is expected that during the round, participants can get acquainted with the language and solve a few simple problems. The language will be announced 30 minutes before the start of the round. At the same time (or earlier but encrypted archives) we will publish the archives with the tools to write programs in this language.

I am pleased to announce that the top 20 participants will receive an exclusive t-shirt, and another 10 random participants among those who solved at least three problems will receive an exclusive t-shirt too.

The rules of the contest are as follows:

• The contest is unrated for everybody.
• The round uses ACM ICPC rules: the standing is defined by the number of solved problems, ties are resolved based on penalty time. Initially the penalty is 0, and for each solved problem it is increased by submission time (since the start of the contest) + 20 minutes for each failed submission. The solution is considered to be correct if it passes all tests from a predefined test set; you know whether the solution is right immediately after sending it. There are no hacks.
• The round will have 8-10 problems, sorted by estimated complexity, and you have 2 hours to solve it.
• Solutions are accepted only in one language, which will be announced in 30 minutes before the contest.
• Please reread this post at the beginning of the contest: we will announce the language and add instructions to install the compiler (the contest interface will provide an option to run your solutions online as well) and links to useful manuals. Other than that, learning the language is up to the competitor. You can use any resources to solve the problems (as long as you remember that this is an individual competition); you don't have to limit yourself to the manuals provided in the post.

Good luck!

Hi everyone!

Codeforces Round #357 (Div. 2) will take place today on the 14th of June at 19:35 MSK.

I am the author of all the problems, and this is my first round on Codeforces. I hope you will enjoy it.

I'd like to thank Gleb GlebsHP Evstropov and Dan danilka.pro Sagunov for helping me in preparing problems, Mike MikeMirzayanov Mirzayanov for the great Codeforces and Polygon platforms, and also Demid BLIZZARD Kucherenko for writing alternative solutions.

There will be five problems and two hours for solving them. The scoring distribution will be announced later.

UPD

Scoring: 500-1000-1500-2000-2500

UPD

Congratulations to winners!

Div. 2

1. pozhaluista
2. Bedge
3. jerjerisfat
4. Huyum_nik
5. OnlyYuju

Div. 1

1. uwi
2. anta
3. kmjp
4. ngfam_kongu
5. BigBag

UPD

Editorial