Hello again, Codeforces!

I'd like to invite you to Codeforces Round #452 (Div. 2). It'll be held on Sunday, December 17 at 09:35 MSK and as usual Div. 1 participants can join out of competition. Note that round starts in the unusual time!

The round is rated.

This round is held on the tasks of the second day of the municipal stage All-Russian Olympiad of Informatics 2017/2018 year in city Saratov. They were prepared by Olympiad center of programmers of Saratov SU. A convincing request to the participants of the municipal stage in Saratov to do not participate in this contest.

Great thanks to Nikolay Kalinin (KAN) and Grigory Reznikov (vintage_Vlad_Makeev) for helping me preparing the contest, to Mike Mirzayanov (MikeMirzayanov) for the great Codeforces and Polygon platform and to Alexey Ripinen (Perforator) for writing solutions.

You will be given six problems and two hours to solve them. The scoring distribution will be published soon. Good luck everyone!

UPD The scoring distribution 500-1000-1500-1750-2250-2500

UPD: The system testing is starting now, but upsolving, virtual participation and viewing solutions and tests will be disabled till the end of the olympiad in Saratov (around 2-3 hours from now). Hope for your understanding. Editorial will be posted after the olympiad as well.

UPD Congratulations to the winners!

1. Spyt

2. taew

3. Fop_zzZ

4. kabuszki

5. Join_VNOI_Discord

UPD Editorial

Hello, Codeforces!

I'd like to invite you to Codeforces Round #451 (Div. 2). It'll be held on Saturday, December 16 at 14:35 MSK and as usual Div. 1 participants can join out of competition. Note that round starts in the unusual time!

The round is rated.

This round is held on the tasks of the municipal stage All-Russian Olympiad of Informatics 2017/2018 year in city Saratov. They were prepared by Olympiad center of programmers of Saratov SU. A convincing request to the participants of the municipal stage in Saratov to do not participate in this contest.

Great thanks to Grigory Reznikov (vintage_Vlad_Makeev) and Nikolay Kalinin (KAN) for helping me preparing the contest, to Mike Mirzayanov (MikeMirzayanov) for the great Codeforces and Polygon platform and to Alexey Ripinen (Perforator) and Roman Glazov (Roms) for writing solutions.

You will be given six problems and two hours to solve them. The scoring distribution 500-750-1500-1750-2000-2500. Good luck everyone!

UPD Editorial

UPD2 Congratulations to the winners!

1. Namys

2. MSeashell

3. zhouyidong

4. ITMO.MansNotHot9

5. meoconn

Hello, Codeforces!

We are pleased to announce the 1st Hello India x Russia Programming Bootcamp, with Amrita School of Engineering, Moscow Institute of Physics and Technology in collaboration with Moscow Workshops ACM ICPC, and of course Codeforces!

The boot camps will be held from March 22nd to the 30th in both India and Russia.

We would like to bring your attention to the new Bootcamp Features: Hello India x Russia Programming Bootcamp and Moscow Workshops ACM-ICPC will be running both boot camps side by side, every day each camp will be competing in parallel, 7,500 kilometers from each other.

In India and Russia, the Coordinators of the Programming Committee will be both Gleb GlebsHP Evstropov and Michael Endagorion Tikhomirov, respectively.

A look back on our recent boot camp:

Hello everyone!

We’re glad to tell you that Moscow Pre-Finals ACM ICPC Workshop will be held at Moscow Institute of Physics and Technology from 21 of March to 1 of April, 2018.

The Moscow Pre-Finals ACM ICPC Workshop is the unique event in the world of competitive programming. Many teams participated in this Workshop turn out to be the prize-winners and winners of the the ACM-ICPC World Finals. In 2017 8 out of 12 teams that were awarded medals at the Finals took part in the Moscow Pre-Finals Workshop ACM ICPC at MIPT.

The Workshop is going to be held in accordance with the two divisions scheme. We invite finalists to participate in the first division and other teams who want to train before the next season in the second division.

The Workshop is organized by MIPT, University ITMO and SPbU.

The official language is English.

The participation cost in payment before 12 of February for one person is $630. The cost includes the full curriculum, food and accommodation at the MIPT campus, as well as the sports and sightseeing schedules on days-off.

More information here.

The Workshop participants will also have an opportunity to give a try at MosCode Festival 2018 which will take place on March 31 and April 1. But we'll tell you about it later)

Hello Codeforces!

On December 12, 18:05 MSK Educational Codeforces Round 34 will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

This round will be rated for Div. 2 again. It will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 7 problems and 2 hours to solve them.

The problems were prepared by Mikhail awoo Piklyaev, Ivan BledDest Androsov and me.

Good luck to all participants!

I also have a message from our partners, Harbour.Space University:

Scholarship Information

We are offering a Scholarship for each of our three tech programmes: Data Science, Computer Science and Cyber Security — fill out the Form for the January 2018 programme start period or the September 2018 programme start period. We will contact you soon. Can't wait to see you here!

Go to form

Congratulations to the winners:

Congratulations to the best hackers:

1528 successful hacks and 786 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

UPD Editorial

Hello everybody!

Congratulations to the platform Codeforces with an Anniversary 450th round!

We are glad to report that Codeforces Round #450 (Div.2) takes place on December 11 19:05 MSK. The round will be rated for Div.2 participants. Traditionally, we invite Div.1 participants to join out of competition. I hope stronger participants also will find interesting problems for themselves:)

The problems are created by me and Nikita slelaron Kostlivcev. We want to show our great appreciation to Nikolay KAN Kalinin for round coordination, mike_live and Arpa for testing the problems and of course Mike MikeMirzayanov Mirzayanov for great platforms Codeforces and Polygon.

You will have 5 problems to solve in 2 hours.

Scoring as usual: 500 — 1000 — 1500 — 2000 — 2500.

Good luck to all and enjoy the problems!

UPD: Contest is finished! I hope you enjoyed the round:)

UPD: Editorial. The problem E will be posted soon.

UPD: The problem E was posted.

Congratulations to the winners!!!

Div 1

1. KrK

2. zscc

3. wwwwodddd

4. uwi

5. oversolver

6. Shayan

7. dreamoon_love_AA

8. please_delete_account

9. alexrcoleman

10. guille

Div 2

1. zeronumber

2. Brightness

3. UBICA

4. Lyon_71

5. mmkh

6. I_Love_Adriana_Chechik

7. Ant_Man

8. yuvalsalant

9. Natsume_Mio

10. PuriceLoh420

Hi, Codeforces!

This is not an ordinary post from me. This is not an announcement of new features or a championship, but I'm no less enthusiastic.

I am glad to inform you that from January 29 to February 16, 2018 I will be giving the course "Advanced Algorithms and Data Structures" in Harbour.Space University (Barcelona, Spain). The course will be in English. The students of this course will not only be students of Harbour.Space, but is open to all! Who wants to join?

This course isn't just for Harbour.Space students, it is also open to Codeforces participants, who will be offered a special price, 1000 EUR. The cost does not include travel or accommodation.

In my plans there is a detailed story about some algorithms and data structures, a lot of practical exercises and emphasis not only on the correctness, but also the beauty and structure of the code. My goal is to make useful and interesting classes for both those who want to understand the fundamental CS, and for those interested in programming competitions. And of course, we will have the opportunity to meet and talk. I'm happy to share stories about the history of Codeforces and development plans.

The course will consist of three weeks of training, 5 training days in each week. The program includes daily lectures and practical exercises. It will not be boring for sure!

Here is the expected course outline:

Harbor.Space University is located in Barcelona (Spain). For users of Codeforces, Harbour.Space is known for active participation in the life of the community of sports programming (partnership with Codeforces in the framework of Educational Rounds). The main activity of the university is teaching (there are bachelor's and master's programs) in the following areas:

• Maths as a Second Language
• Computer Science
• Data Science
• Cyber Security
• Interaction Design
• Digital Marketing
• High Tech Entrepreneurship
• FinTech
• BioTech
• Aerospace Engineering
• SuperCities UrbanTech

Register for my upcoming course here.

Mike Mirzayanov

Let us introduce the new programming language in ICPC: Kotlin. It is modern and developing language created by our sponsor JetBrains. Kotlin is inspired by Java and as Java is named after the island. Currently, Kotlin programs are compiled into JVM bytecode, all Java written code can be used from Kotlin sources and Kotlin written code can be used from Java sources as well out of the box. Kotlin being developed now most of the standard libraries are Java library classes, making Kotlin a programing language that is already used in many projects being the main language of their development.

Comparing to Java language some Java disadvantages fixed and new features added. Some of them we will see in today's solution of ICPC World Finals 2016 problem C (101242C - Ceiling Function). Less boilerplate code and syntactic sugar added

1. new operator omitted
2. data classes implement hashCode, equals and toString methods depending on constructor parameters
3. operator overloading
4. with function, to implement a block of code, making captured value as this
5. when operator providing better readability of conditional operator in some cases
6. type inference (IDE supports hints on variable and function types, it's just you don't have to type it)
7. functional programming style

import java.util.*

data class Tree(var left: Tree? = null, var right: Tree? = null) {
    var value = 0
}

operator fun Tree?.plus(x: Int): Tree? {
    if (this == null) return Tree().apply { value = x }
    if (x < value) {
        left += x
    } else {
        right += x
    }
    return this
}

fun main(args: Array<String>) = with(Scanner(System.`in`)) {
    val n = nextInt()
    val k = nextInt()
    val a = Array(n) { IntArray(k) { nextInt() } }
    println(a.map { it.fold(null, Tree?::plus) }.toSet().size)
}

You can try Kotlin at: https://try.kotlinlang.org