### BledDest's blog

By BledDest, 3 months ago,

We hope you enjoyed the problems! Thank you for participation.

The authors are the usual suspects: Neon, awoo, adedalic, Roms and me. Huge thanks to the testers: shnirelman, KIRIJIJI, soup, Optoed, le.mur, and the MVP tester PavelKunyavskiy. Without your insights, this round would be impossible!

1958A - 1-3-5

Idea: BledDest, preparation: BledDest

Tutorial
Solution (PavelKunyavskiy)

1958B - Clock in the Pool

Tutorial
Solution (PavelKunyavskiy)

1958C - Firewood

Idea: BledDest, preparation: BledDest

Tutorial
Solution (PavelKunyavskiy)

1958D - Staircase

Idea: BledDest, preparation: BledDest

Tutorial
Solution (PavelKunyavskiy)

1958E - Yet Another Permutation Constructive

Idea: BledDest, preparation: BledDest

Tutorial
Solution (PavelKunyavskiy)

1958F - Narrow Paths

Idea: BledDest, preparation: awoo

Tutorial
Solution (PavelKunyavskiy)

1958G - Observation Towers

Idea: BledDest, preparation: awoo

Tutorial
Solution (PavelKunyavskiy)

1958H - Composite Spells

Idea: Roms, preparation: Roms

Tutorial
Solution (Neon)

1958I - Equal Trees

Idea: BledDest, preparation: Neon

Tutorial
Solution (PavelKunyavskiy)

1958J - Necromancer

Idea: BledDest, preparation: Neon

Tutorial
Solution (Neon)
• +32

By BledDest, history, 3 months ago,

Greetings Codeforces!

First things first, we would like to thank everyone who participated in the previous nine Kotlin Heroes competitions: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, Episode 8 and Episode 9.

Kotlin Heroes is a great way to play around with Kotlin’s features, learn something new, and practice using the language by solving fun problems. It is great for programmers of any level!

We invite you to join the practice round, where you can improve your algorithmic problem-solving skills and complete training problems. In this round, all the solutions are open and you can request hints if you’re stuck.

On May 13, 2024, the real challenge begins! Kotlin Heroes: Episode 10 will last 2 hours 30 minutes and will feature a set of problems ranging from simple ones, which are designed to be solvable by anyone, to some really tricky ones for seasoned competitive programmers.

REGISTER →

You can solve Codeforces challenges directly from your JetBrains IDE using its smart features. Just enable the JetBrains Academy plugin and follow the instructions in the Getting started with Codeforces guide.

Prizes:

The top three winners will receive cash prizes of $512,$256, and $128 (or rewards of equivalent value), respectively. The top 50 participants will win a Kotlin Heroes T-shirt and an exclusive Kotlin sticker, and all competitors who solve at least one problem will be entered into a raffle for one of 50 Kotlin Heroes T-shirts. Please note that we are not able to ship prizes to any country, state, province, or territory subject to comprehensive OFAC sanctions, including Belarus, Cuba, Iran, North Korea, Russia, Syria, or the Crimea, Donetsk, or Luhansk regions. To see the list of sanctioned countries and regions, please visit this page. Best of luck to everyone! Announcement of Kotlin Heroes: Episode 10 Announcement of Kotlin Heroes: Practice 10 • +74 By BledDest, history, 8 months ago, 1913A - Rating Increase Idea: Roms, preparation: awoo Tutorial Solution (awoo) 1913B - Swap and Delete Idea: BledDest, preparation: adedalic Tutorial Solution (adedalic) 1913C - Game with Multiset Idea: Ferume, preparation: Ferume Tutorial Solution (awoo) 1913D - Array Collapse Idea: Roms, preparation: Roms Tutorial Solution (Roms) 1913E - Matrix Problem Idea: Ferume, preparation: Ferume Tutorial Solution (BledDest) 1913F - Palindromic Problem Idea: Ferume, preparation: Ferume Tutorial Solution (awoo) • +25 By BledDest, history, 8 months ago, Hello Codeforces! 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 the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally. You will be given 6 or 7 problems and 2 hours to solve them. The problems were invented and prepared by Adilbek adedalic Dalabaev, Mikhail awoo Piklyaev, Maksim Neon Mescheryakov, Roman Roms Glazov, Artem Ferume Ilikaev, Ruslan AcidWrongGod Kapralov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces. The problemset partially intersects with the Open KFU Olympiad, so if you participated in it, please avoid taking part in the round. Good luck to all the participants! Our friends at Harbour.Space also have a message for you: WORK & STUDY OPPORTUNITY IN BARCELONA @ HARBOUR.SPACE UNIVERSITY Harbour.Space University has partnered with Giga (Unicef) to offer Master’s degree scholarships in the fields of Data Science, Computer Science and Front-end Development, as well as work experience. We are looking for various junior to mid-level candidates: Data Scientist: • Strong ML knowledge • Experience with Data Visualization Tools like matplotlib, ggplot, d3.js., Tableau that help to visually encode data • Excellent Communication Skills – describing findings to a technical and non-technical audience is essential • Strong Software Engineering Background • Hands-on experience with data science tools • Problem-solving aptitude • Analytical mind and great business sense • Degree in Computer Science, Engineering or relevant field is preferred Data Analyst: • Cleansing and preparing data • Analyzing and exploring data • Expertise in statistics • Analyzing and visualizing data • Reports and dashboards • Communication and writing • Expertise in the domain • Solution-oriented Front-end Developer: • Solid understanding of HTML, CSS, and JavaScript • Familiarity with front-end frameworks and tools such as React or Vue.js. • Strong problem-solving skills, attention to detail, and a passion for creating intuitive user interfaces are essential Full-stack Developer: • Interest and experience in web application development, data products and OpenAPIs • Comfortable with on-cloud deployment services (preferably Azure), Git and CI/CD pipeline and deployment processes • Experience with open-source projects is highly preferred • Strong ML knowledge • Experience with data visualization tools like matplotlib, ggplot, d3.js, Tableau that help to visually encode data • Excellent communication skills, — it is incredibily important to describe findings to a technical and non-technical audience • Strong software engineering background • Hands-on experience with data science tools • Problem-solving aptitutde • Analytical mind and great business sense • Degree in computer science, engineering or relevant field is preferred All successful applicants will be eligible for a 100% tuition fee scholarship (29,900 €/year) provided by the partner company. CANDIDATE’S COMMITMENT Study Commitment: 3 hours/day You will complete 15 modules (each three weeks long) in one year. Daily class workload is 3 hours, plus homework to complete in your own time. Work Commitment: 4+ hours/day Immerse yourself in the professional world during your apprenticeship. You’ll learn from the best and get to apply your newly acquired knowledge in the field from day one. REQUIREMENTS: • Industry experience • International exposure • Eager to learn • Sustainability is a key topic for you • You want to work for an NGO Apply here → • +53 By BledDest, 8 months ago, The contest was prepared by awoo, Neon, adedalic, Roms and me. We are very grateful to all of the testers of the contest: PavelKunyavskiy, ashmelev, vladmart, Vladosiya and mariibykova. We hope you enjoyed both the problems and coding in Kotlin! Okay, now let's talk about how these problems can be solved: 1910A - Username Idea: BledDest, preparation: Neon Tutorial Solution (PavelKunyavskiy) 1910B - Security Guard Idea: Roms, preparation: Roms Tutorial Solution (Neon) 1910C - Poisonous Swamp Idea: BledDest, preparation: awoo Tutorial Solution (PavelKunyavskiy) 1910D - Remove and Add Idea: BledDest, preparation: awoo Tutorial Solution (PavelKunyavskiy) 1910E - Maximum Sum Subarrays Idea: BledDest, preparation: Neon Tutorial Solution 1 (Neon) Solution 2 (PavelKunyavskiy) 1910F - Build Railway Stations Idea: BledDest, preparation: awoo Tutorial Solution (PavelKunyavskiy) 1910G - Pool Records Idea: adedalic, preparation: adedalic Tutorial Solution (adedalic) 1910H - Sum of Digits of Sums Idea: BledDest, preparation: BledDest Tutorial Solution (PavelKunyavskiy) 1910I - Inverse Problem Idea: BledDest, preparation: awoo Tutorial Solution (awoo) 1910J - Two Colors Idea: BledDest, preparation: BledDest Tutorial Solution (PavelKunyavskiy) • +35 By BledDest, 8 months ago, Greetings Codeforces! We are thrilled to announce the return of Kotlin Heroes! As we resume this competition, we're eager both to welcome back some familiar names and meet new participants. Let's make Kotlin Heroes: Episode 9 an occasion to remember! We would like to thank everyone who participated in the previous eight Kotlin Heroes competitions: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, and Episode 8. Kotlin Heroes is a great way to play around with Kotlin’s features, learn something new, and practice using the language by solving fun problems. It is great for programmers of any level! We invite you to join the practice round, where you can hone your algorithmic problem-solving skills and complete training problems. In this round, all the solutions are open and you can request hints if you’re stuck. Here are some things you can do to help you refresh your knowledge of Kotlin and learn more about competitive programming while you practice: On December 11, 2023, the real challenge begins! Kotlin Heroes: Episode 9 will last 2 hours 30 minutes and will feature a set of problems ranging from simple ones, which are designed to be solvable by anyone, to some really tricky ones for seasoned competitive programmers. REGISTER → You can solve Codeforces challenges directly from your JetBrains IDE using its smart features. Just enable the JetBrains Academy plugin and follow the instructions in the Getting started with Codeforces guide. Prizes: The top three winners will receive cash prizes of$512, $256, and$128 (or rewards of equivalent value), respectively. The top 50 participants will win a Kotlin Heroes T-shirt and an exclusive Kotlin sticker, and all competitors who solve at least one problem will be entered into a raffle for one of 50 Kotlin Heroes T-shirts.

Please note that we are not able to ship prizes to any country, state, province, or territory subject to comprehensive OFAC sanctions, including Belarus, Cuba, Iran, North Korea, Russia, Syria, or the Crimea, Donetsk, or Luhansk regions. To see the list of sanctioned countries and regions, please visit this page.

Best of luck to everyone!

UPD: The round tutorial has been published at the following link: https://codeforces.com/blog/entry/123261.

• +88

By BledDest, 10 months ago,

1879A - Rigged!

Idea: Roms

Tutorial
Solution (Roms)

1879B - Chips on the Board

Idea: BledDest

Tutorial
Solution (Neon)

1879C - Make it Alternating

Idea: Roms

Tutorial
Solution (Roms)

1879D - Sum of XOR Functions

Idea: Roms

Tutorial
Solution (Roms)

1879E - Interactive Game with Coloring

Idea: BledDest

Tutorial
Solution (BledDest)

1879F - Last Man Standing

Idea: BledDest

Tutorial
Solution (awoo)
• +76

By BledDest, 12 months ago,

I don't think comments like "you use X in model solution, author, are you an idiot?", "f**k you and your problems, they are shit" and such should be normal on Codeforces, especially when written by someone high-rated and/or respected in the community. I also don't think this kind of behavior should be normal towards regular users.

I know that sometimes contests can be frustrating. Sometimes it is the participant's fault, sometimes it is the problemsetter's fault, sometimes it just happens without anyone being guilty of that. And I understand that in some cases, the criticism the author receives is fair and well-deserved.

But there is a fine line between criticism, saying that you didn't like the problems, and hurling insults against the author. The former two are acceptable (and sometimes even needed, because authors have to improve and learn from their mistakes); the latter one, in my opinion, should not be acceptable.

It's not like we can ever get rid of offense and hatred completely; there will always be people who want to take it out on the community as a whole or someone specific. And if I created a blog for every time I saw an insult hurled towards me or some other member of the community, my account would already be banned for spamming. But I think that the comments like the one linked in the first paragraph are especially dangerous and need to be dealt with.

Codeforces community is biased towards people with high rating and people who do something for the website. And this is sometimes a good thing; but it can also make people think that if a high-rated participant and a problemsetter allows himself (or herself) to be rude and offensive, then it is acceptable, and they are allowed to do it as well. That's why cases like this one are especially bad.

We can never get rid of offense and hatred, but please don't make it something normal. Everyone should be responsible for what they are saying or writing, but if your word has some weight in the community, then it also means some additional responsibility for you. Please don't make people think that insulting the author (or anyone else, for that matter!) is perfectly reasonable and fine — I doubt you will like the results of that.

UPD: It looks like the focus of the comment section has shifted towards discussing how to give constructive feedback to the problemsetters. This is certainly one of the points of the blog, but the main thing I wanted to state was that insults against anyone should not be acceptable. It's just that the problemsetters usually get the most of the hatred on CF, so it's much easier to find the examples of that. But this behavior towards regular users should not be allowed either.

UPD2: Initially, there was a link to the comment which caused me to write this whole blog (a comment by a high-rated user and a problemsetter when he openly called another problemsetter retarded because of some details of the solution). I wanted to show it as a clear example, but it was not the right thing to do.

To the person whose comment I used as an example (if you're reading this): I apologize, I shouldn't have made it seem like you're the culprit, and I didn't understand the consequences of my blog fully. I know that you have openly admitted your mistake, and I admire you for that. If the fact that I've used you as an example made you feel awful, or made some other people call you out — I am terribly sorry.

• +2126

By BledDest, 12 months ago,

1849A - Morning Sandwich

Idea: BledDest

Tutorial
Solution (awoo)

1849B - Monsters

Idea: BledDest

Tutorial
Solution (Neon)

1849C - Binary String Copying

Idea: BledDest

Tutorial
Solution (vovuh)

1849D - Array Painting

Idea: BledDest

Tutorial
Solution (BledDest)

1849E - Max to the Right of Min

Idea: awoo

Tutorial
Solution (awoo)

1849F - XOR Partition

Idea: BledDest

Tutorial
Solution (BledDest)
• +102

By BledDest, history, 12 months ago, translation,

Hello Codeforces!

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 the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 6 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Mikhail awoo Piklyaev, Maksim Neon Mescheryakov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

WORK & STUDY OPPORTUNITY IN BARCELONA @HARBOUR.SPACE UNIVERSITY

Harbour.Space University has partnered with Giga (Unicef) to offer Bachelor's and Master’s degree scholarships in the fields of Data Science, Computer Science and Front-end Development as well as work experience.

We are looking for various junior to mid level candidates:

Data Scientist:

• Strong ML knowledge
• Experience with Data Visualization Tools like matplotlib, ggplot, d3.js., Tableau that help to visually encode data
• Excellent Communication Skills – it is incredibly important to describe findings to a technical and non-technical audience.
• Strong Software Engineering Background
• Hands-on experience with data science tools
• Problem-solving aptitude
• Analytical mind and great business sense
• Degree in Computer Science, Engineering or relevant field is preferred

Data Analyst:

• Cleansing and preparing data
• Analyzing and exploring data
• Expertise in statistics
• Analyzing and visualizing data
• Reports and dashboards
• Communication and writing
• Expertise in the domain
• Solution-oriented

Front-end Developer:

This student will work closely with the blockchain developer and product lead to contribute to the design and implementation of user interfaces for the company's blockchain-based prototypes. They will be responsible for translating UI/UX design wireframes into functional and visually appealing web applications, ensuring seamless user experiences. The student will collaborate with blockchain and backend developers and designers to integrate front-end components with server-side logic and optimize application performance. They will also be involved in testing, debugging, and maintaining the front-end codebase. The intern will have the opportunity to gain practical experience in front-end development within the context of blockchain technology and contribute to the Giga’s mission of connecting schools to the internet.

• Solid understanding of HTML, CSS, and JavaScript
• Familiarity with front-end frameworks and tools such as React or Vue.js.
• Strong problem-solving skills, attention to detail, and a passion for creating intuitive user interfaces are essential

Full Stack Developer:

• Interest and experience in web application development, data products and OpenAPIs
• Comfortable with on-cloud deployment services (preferably Azure), Git and CI/CD pipeline and deployment processes
• Experience with open-source projects is highly preferred

All successful applicants will be eligible for a 100% tuition fee scholarship (29.900 €/year) provided by the partner company.

CANDIDATE’S COMMITMENT

Study Commitment: 3 hours/day

You will complete 15 modules (each three weeks long) in one year. Daily class workload is 3 hours, plus homework to complete in your own time.

Work Commitment: 4+ hours/day

Immerse yourself in the professional world during your apprenticeship. You’ll learn from the best and get to apply your newly acquired knowledge in the field from day one.

REQUIREMENTS:

• Industry experience
• International exposure
• Eager to learn
• Sustainability is a key topic for you
• You want to work for an NGO
Apply Now →

UPD: The editorial has been published.

• +322

By BledDest, 14 months ago,

So, first of all, I would like to apologize for the issue with the problem B in today's ER. We tried to fix it as quick as possible, but unfortunately, still lots of submissions were made and this caused a big queue during the round. I am sorry for this.

How did this all happen? Well, this is really a sad story about one commit.

About three hours before the round, while writing explanations for the problem B statement, I noticed that the answers were different from the correct values by 1. I opened the model solution in another tab in Polygon, wrote +1 to the value I printed, clicked "Save" and then committed the changes (including the notes for the samples). But, unfortunately, that change in the model solution wasn't included in the commit.

The cause was that the model solution didn't save in time for the commit (and actually never saved for some reason, maybe some bug in the browser or Internet connection issues). I didn't notice that, and while rereading the problem again, I never checked that part because "well, I fixed that thing, it is definitely correct now!"

The point of the story? Always recheck what you're actually committing. Always double-check even the parts of the problem you have already fixed, even if you're sure that after all the changes you've done, they're 100% correct.

I am again deeply sorry for the problems it has caused, and I hope that it won't happen again.

• +385

By BledDest, 15 months ago,

1821A - Matching

Idea: BledDest

Tutorial
Solution (BledDest)

1821B - Sort the Subarray

Idea: BledDest

Tutorial
Solution (BledDest)

1821C - Tear It Apart

Idea: BledDest

Tutorial
Solution (awoo)

1821D - Black Cells

Tutorial

1821E - Rearrange Brackets

Idea: BledDest

Tutorial
Solution 1 (awoo)
Solution 2 (awoo)

1821F - Timber

Idea: BledDest

Tutorial
Solution (awoo)
• +78

By BledDest, 18 months ago,

In the recent months, the number of trash blogs on Codeforces has risen. Thankfully, they are mostly being ignored, and are very often recognizable by their title and/or author handle, but they still show up in the Recent Actions, making navigation through actually meaningful and good content like tutorials/contest invitations/etc harder. And very often, it's the same person posting one useless blog after another, not getting banned even after five or six instances. Personally, I am sick of those blogs, and I don't think I'm the only one.

I understand why they don't get banned. Mike, Gera Nazarov and other people responsible for the platform are very busy maintaining the testing system, catching cheaters, improving Polygon and doing other work which lets Codeforces continue running and improving. They don't have time for digging through everything that gets posted, and that's perfectly understandable.

So, I think we need some other people who can do this. Maybe a crew of some universally trusted contributors can volunteer for the job of cleaning Codeforces from garbage blogs and people who post them? (If I were asked, I'd volunteer.) I don't think they'll be able to resolve the whole issue, since some people will definitely register a new account to post all sorts of BS on the platform, but I believe it will at least reduce the number of such blogs. The current system when someone can avoid getting banned after posting even, like, five or six trash blogs doesn't mitigate this issue.

Some other possible solutions for the issue (and why I think they won't work):

Maybe automatically take away the ability to post blogs when you reach certain negative contribution?
Maybe impose a stricter constraint on the ability to post blogs, instead of the current one, which is simply getting a submission accepted?
Maybe design an AI to filter blogs?

Poll:

I am annoyed by useless blogs, and I think CF needs a moderation system

I am annoyed by useless blogs, but I don't think that moderation system will improve the situation

I am annoyed by useless blogs, and I think there is a better solution than moderation system

I am annoyed by useless blogs, but I don't think anything needs to be done

I usually don't notice useless blogs

I think everyone should have the ability to post whatever they want

• +244

By BledDest, history, 20 months ago,

1765A - Access Levels

Idea: BledDest, preparation: awoo

Tutorial
Solution (awoo)

1765B - Broken Keyboard

Idea: vovuh, preparation: vovuh

Tutorial
Solution (vovuh)

1765C - Card Guessing

Idea: DStepanenko, preparation: BledDest

Tutorial
Solution (awoo)

1765D - Watch the Videos

Idea: BledDest, preparation: DmitryKlenov

Tutorial
Solution (DmitryKlenov)

1765E - Exchange

Idea: BledDest, preparation: BledDest

Tutorial
Solution (BledDest)

1765F - Chemistry Lab

Idea: awoo, preparation: awoo

Tutorial
Solution (awoo)

1765G - Guess the String

Idea: BledDest, preparation: BledDest

Tutorial
Solution (BledDest)

1765H - Hospital Queue

Idea: Neon, preparation: Neon

Tutorial
Solution (Neon)

1765I - Infinite Chess

Idea: DmitryKlenov, preparation: dmitryme

Tutorial
Solution (awoo)

1765J - Hero to Zero

Idea: BledDest, preparation: BledDest

Tutorial
Solution (BledDest)

1765K - Torus Path

Tutorial

1765L - Project Manager

Idea: BledDest, preparation: awoo

Tutorial
Solution (awoo)

1765M - Minimum LCM

Idea: BledDest, preparation: Neon

Tutorial
Solution (Neon)

1765N - Number Reduction

Idea: Neon, preparation: Neon

Tutorial
Solution (Neon)
• +50

By BledDest, 20 months ago,

Hello Codeforces!

The Southern and Volga Russian Regional Contest was held in Saratov State University on 22nd of November. This contest was used to qualify the teams from Southern Russia and Volga region to the Northern Eurasia Finals.

On Nov/27/2022 13:35 (Moscow time), we will conduct the online mirror of this contest. It will last for 5 hours and is best suited for teams of three people, although it is not forbidden to participate in teams of smaller/larger size. The mirror will use ICPC rules, the same as the offline contest.

I would like to express my gratitude to all other jury members: awoo, Neon, vovuh, adedalic, DmitryKlenov, dmitryme, DStepanenko, elena and kuviman. Also, big thanks to the contest testers: IlyaLos, Oleg_Smirnov, ashmelev, pashka, and especially MikeMirzayanov not only for testing the problems, but also for his excellent Polygon system, without which it would be almost impossible to prepare the competition.

As a chief judge of the contest, I hope you enjoy the problems!

Of course, the contest will be unrated.

upd: The editorial can be found here.

• +210

By BledDest, 2 years ago,

Given the current circumstances, we have decided to postpone Kotlin Heroes until further notice. Thank you for your understanding.

Hello, Codeforces!

First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the eight Kotlin Heroes competitions which were held previously: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, and Episode 8.

Ready to challenge yourself to do better? The [contest:1643] competition will be hosted on the Codeforces platform on [contest_time:1643]. The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programmers.

Prizes:

Top three winners will get prizes of $512,$256, and $128 respectively, top 50 will win a Kotlin Heroes t-shirt and an exclusive Kotlin sticker, competitors solving at least one problem will enter into a draw for one of 50 Kotlin Heroes t-shirts. Registration is already open and available via the link. It will be available until the end of the round. The round will again be held in accordance with a set of slightly modified ICPC rules: • The round is unrated. • The contest will have 9 or 10 problems of various levels of complexity. • You are only allowed to use Kotlin to solve these problems. • Participants are ranked according to the number of correctly solved problems. Ties are resolved based on the lowest total penalty time for all problems, which is computed as follows. For each solved problem, a penalty is set to the submission time of that problem (the time since the start of the contest). An extra penalty of 10 minutes is added for each failed submission on solved problems (i. e., if you never solve the problem, you will not be penalized for trying that problem). If two participants solved the same number of problems and scored the same penalty, then those of them who had previously made the last successful submission will be given an advantage in the distribution of prizes and gifts. REGISTER → If you are still new to Kotlin we have prepared a tutorial on competitive programming in Kotlin and [contest:1645], where you can try to solve a few simple problems in Kotlin. The practice round is available by the link. We made an announcement about the Kotlin Heroes: Episode 9 practice stream, but unfortunately we had to cancel it. Sorry for the inconvenience! We wish you luck and hope you enjoy Kotlin. • +82 By BledDest, 3 years ago, 1633A - Div. 7 Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) 1633B - Minority Idea: BledDest, preparation: awoo and Neon Tutorial Solution (awoo) 1633C - Kill the Monster Idea: BledDest, preparation: Neon Tutorial Solution (awoo) 1633D - Make Them Equal Idea: BledDest, preparation: Neon Tutorial Solution (Neon) 1633E - Spanning Tree Queries Idea: BledDest, preparation: awoo Tutorial Solution (awoo) 1633F - Perfect Matching Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) • +107 By BledDest, 3 years ago, 1618A - Polycarp and Sums of Subsequences Idea: Brovko, preparation: Brovko Tutorial Solution (Brovko) 1618B - Missing Bigram Idea: BledDest, preparation: awoo Tutorial Solution (awoo) 1618C - Paint the Array Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) 1618D - Array and Operations Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) 1618E - Singers' Tour Idea: shnirelman, preparation: shnirelman Tutorial Solution (shnirelman) 1618F - Reverse Idea: Lankin, preparation: Lankin Tutorial Solution (awoo) Solution (BledDest) 1618G - Trader Problem Idea: BledDest, preparation: BledDest Tutorial Solution (awoo) Solution (BledDest) • +93 By BledDest, 3 years ago, translation, Hello, Codeforces! On Dec/14/2021 17:35 (Moscow time) the Codeforces Round 760 (Div. 3) will start. This is a usual round for the participants from the third division. The round will contain 8 problems, which are mostly suited for participants with rating below 1600 (or we hope so). Although, as usual, participants with rating of 1600 and greater can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks (we hope that our tests are strong enough, so there won't be too many solutions hacked during this phase). You will have to solve 8 problems in 2 hours and 15 minutes. The penalty for a wrong submission is equal to 10 minutes. We remind you that only the trusted participants of the third division will be included in the official standings table. As it is written on the blog which you can access by this link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must: • take part in at least two rated rounds (and solve at least one problem in each of them), • not have a point of 1900 or higher in the rating. Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you. The problems were prepared by Brovko, shnirelman, Lankin, awoo and me. We would like to thank the testers of the round: vovuh, Nil_Sinyaev, IsaacMoris, altynai, MarcosK, osylai, ZulaMostafa, nondeterministic, mumumucoder, peroon and kocko. And, the last but not the least, thanks to Mike MikeMirzayanov Mirzayanov for Codeforces and Polygon systems! Good luck in the contest! I hope you'll enjoy solving the problems we have prepared. UPD: The editorial is out. • +336 By BledDest, 3 years ago, translation, 1612A - Distance Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) 1612B - Special Permutation Idea: MikeMirzayanov, preparation: MikeMirzayanov Tutorial Solution (BledDest) 1612C - Chat Ban Idea: vovuh, preparation: vovuh Tutorial Solution (vovuh) 1612D - X-Magic Pair Idea: vovuh, preparation: vovuh Tutorial Solution (vovuh) 1612E - Messages Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) 1612F - Armor and Weapons Idea: BledDest, preparation: BledDest Tutorial Solution (BledDest) 1612G - Max Sum Array Idea: adedalic, preparation: adedalic Tutorial Solution (adedalic) • +87 By BledDest, 3 years ago, Hello Codeforces! On Oct/10/2021 12:05 (Moscow time) Educational Codeforces Round 115 (Rated for Div. 2) will start. Note that the start time is unusual. 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 the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally. You will be given 6 or 7 problems and 2 hours to solve them. The problems were invented and prepared by Alex fcspartakm Frolov, Mikhail awoo Piklyaev, Max Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces. Good luck to all the participants! Our friends at Harbour.Space also have a message for you: Hello once again, Codeforces! We are thrilled to congratulate our faculty member Nikolay KAN Kalinin on his first place at the ICPC World Finals, celebrated in Moscow, Russia. Years of training by Nikolai and his team from Nizhny Novgorod State University lead them to the top of the scoreboard, defeating teams from 116 other universities and becoming world champions. We would also like to congratulate our future student Egor 244mhq Dubovik, who won the silver medal with the Belarusian State University. Egor will join our Masters in Computer Science in the coming weeks. We are looking forward to seeing Nikolay again next January when he teaches his course on Advanced Algorithms and Data Structures alongside Mike Mirzayanov. In this course, students focus on key and in-depth algorithms and data structures that form a modern computer specialist’s toolkit. We are always excited to see Codeforces participants as our students here at Harbour.Space, so once again we’ve given a special discount (up to 70%) for the single course participation in Barcelona, Spain (travel cost and accommodation are not included). Reserve your spot → Good luck on your round, and see you next time! Harbour.Space University • +310 By BledDest, 3 years ago, First of all, I would like to thank all testers of the round: pashka, FlakeLCR, peti1234, Akulyat, bugdone, pacha2880. Also huge thanks to co-authors of the contest: Neon, adedalic and awoo. I hope you enjoyed participating in the round! Okay, now for the editorial itself: 1571A - Sequence of Comparisons Idea: BledDest, preparation: Neon Tutorial Solution (Neon) 1571B - Epic Novel Idea: BledDest, preparation: adedalic Tutorial Solution (adedalic) 1571C - Rhyme Idea: BledDest, preparation: adedalic Tutorial Solution (adedalic) 1571D - Sweepstake Idea: BledDest, preparation: adedalic Tutorial Solution (adedalic) 1571E - Fix the String Idea: BledDest, preparation: Neon Tutorial Solution (pashka) 1571F - Kotlinforces Idea: BledDest, preparation: BledDest Tutorial Solution (pashka) 1571G - A Battle Against a Dragon Idea: BledDest, preparation: awoo Tutorial Solution (awoo) 1571H - Laser Beams Idea: BledDest, preparation: BledDest Tutorial Solution (pashka) 1571I - Physical Examination Idea: BledDest, preparation: awoo Tutorial Solution (awoo) 1571J - Two Railroads Idea: BledDest, preparation: BledDest Tutorial Solution (pashka) • +60 By BledDest, 3 years ago, Hello, Codeforces! First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the seven Kotlin Heroes competitions which were held previously: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, and Episode 7. Ready to challenge yourself to do better? The Kotlin Heroes: Episode 8 competition will be hosted on the Codeforces platform on Oct/07/2021 17:35 (Moscow time). The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programmers. Prizes: Top three winners will get prizes of$512, $256, and$128 respectively, top 50 will win a Kotlin Heroes t-shirt and an exclusive Kotlin sticker, competitors solving at least one problem will enter into a draw for one of 50 Kotlin Heroes t-shirts.

Registration is already open and available via the link. It will be available until the end of the round.

The round will again be held in accordance with a set of slightly modified ICPC rules:

• The round is unrated.
• The contest will have 10 problems of various levels of complexity.
• You are only allowed to use Kotlin to solve these problems.
• Participants are ranked according to the number of correctly solved problems. Ties are resolved based on the lowest total penalty time for all problems, which is computed as follows. For each solved problem, a penalty is set to the submission time of that problem (the time since the start of the contest). An extra penalty of 10 minutes is added for each failed submission on solved problems (i. e., if you never solve the problem, you will not be penalized for trying that problem). If two participants solved the same number of problems and scored the same penalty, then those of them who had previously made the last successful submission will be given an advantage in the distribution of prizes and gifts.

REGISTER →

If you are still new to Kotlin we have prepared a tutorial on competitive programming in Kotlin and Kotlin Heroes: Practice 8, where you can try to solve a few simple problems in Kotlin. The practice round is available by the link.

And last but not the least: two-time ICPC World Champion and winner of four previous Kotlin Heroes episodes Gennady tourist Korotkevich will be featured in a livecoding session, conducted by JetBrains, where he is going to show how to solve the problems from the Practice round, so you can learn how to use Kotlin in contests from the most famous competitive programmer in the world. The JetBrains Presentation and livecoding session from Gennady will be streamed on ICPC Live and Kotlin YouTube channel. The stream starts at 10 a. m. on the 2nd of October, Moscow time (UTC+3), you can join the stream by the link.

We wish you luck and hope you enjoy Kotlin.

Announcement of Kotlin Heroes: Practice 8
Announcement of Kotlin Heroes: Episode 8
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