Ciao, Codeforces! We're glad to invite you to take part in Pinely Round 3 (Div. 1 + Div. 2), which will start on Dec/23/2023 17:35 (Moscow time). You will be given 9 problems and 3 hours to solve them. One of the problems will be divided into two subtasks.

The problems were authored and prepared by me.

We would like to thank

• errorgorn for his fun 🤌 🤡 🤓 😩 coordination;
• Alexdat2000 for Russian translation;
• franv for writing $$$173$$$ lines of checker of problem H correctly at the first try;
• franv for pictures in the editorial;
• dario2994, Endagorion, ffao, Golovanov399, nor for VIP testing;
• Kaey, MrBrionix, lorenzoferrari, nicksms, fwitt, milind0110, jamesbamber, alls, dorijanlendvaj, sunsh1ne, BrehamPie, 31ballons, gamegame, AndreySergunin, zeliboba, Jarnsida, I_L0Ve_MySelF, 1L1YA, MrAndria, TheRubbish, omsincoconut, jerefigo, dazlersan1, t0rtik, nondeterministic, SetBackIsBest, vantaablackk, htetgm, BestCrazyNoob, LaMatematica14, OgradL, bitset, magnus.hegdahl, Mirali777, Nika533, silxi, ttamx, ApraCadabra, pera2008, Sokol080808, A_G for testing;
• MikeMirzayanov for creating Codeforces and Polygon.

Score distribution: $$$500 - 1000 - 1500 - 2000 - 2500 - (1500 + 1500) - 4000 - 6000 - 6000$$$

We hope you'll like the problemset!

Update 1: the editorial is here.

Update 2: congratulations to the winners!

This round is made possible with the support of Pinely!

Pinely is an algorithmic trading firm, with its main focus set on high-frequency and ultra-low-latency trading. They have offices in Amsterdam, Limassol, Singapore, and Shanghai and are open for job discussions. Pinely is a team of winners, awardees, and medalists of various competitions in respective fields such as ICPC, IMC, HITB PRO CTF, and Google HashCode, etc. They constantly face various challenges such as developing strategies for trading, optimizing trading systems to achieve the lowest latency reactions to various market events, and saving and processing large volumes of historical data.

You can find out more about Pinely on their website or from their employees registered here on Codeforces. If you want to join the Pinely team, please send your CV to [email protected] or fill in the form:

Prizes: top 30 contestants and 10 random contestants placed 31-100 will receive a branded Pinely hoodie :)

Dear Santa Claus. Please make 2024 a happy year, not just that. Please, we all need this.

Hello, 2024!

And we have traditional gifts!

Change Handle Feature

Hurry! Only until the 10th of January, you can change your handle (but only once)! Note that it will be possible to roll back the changes or change the handle again only after a year. Be careful what you wish for.

You can change your handle to the new one that wasn't used before by anybody or which was used by you before. The links to a profile page with an old handle would automatically redirect to the actual profile.

Again, this year if you took part in at least 10 rounds you can request a handle of an inactive participant. It means that the participant should have a period of activity on Codeforces of at most 180 days, this period should be in 2020 or earlier. The inactive participant can't have posted comments, messages, and so on. It can't take part in more than 2 contests. It will be automatically renamed and informed by email. A user has the opportunity to request back his/her handle: in this case, we will roll back the change and return your previous handle to you. If you can't change your handle to another, it means that some requirements don't meet. Please do not ask me to do something with it. Especially, I do not like requests like "this is my second account, I took an interesting handle myself". I'm not Santa Claus.

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 ..."

New Year's Masquerade of Colors and Ranks

The traditional magical tab has appeared in the profile setting. Happy New Year!

Hello, Codeforces!

I'm happy to invite the Codeforces community to join an unusual competition organized by our title sponsor, the TON Foundation.

The competition will revolve around programming smart-contracts in FunC, native to the TON ecosystem. We invite the Codeforces community to participate in this contest and show that they can not only solve algorithmic problems in rounds but also delve into a new and interesting area.

Join the contest and master complex cell manipulations, smart contract storage organization, comment handling, basic cryptography, and the logic of governance smart contracts through problem-solving.

The tasks will go live on December 21, and the submission deadline is December 30 at 23:59:59 (UTC+4). To enter the challenge, register via the @smartchallengebot on Telegram. The bot will assist you throughout the registration process and send you notifications with the latest updates, such as the start of the contest or the tasks. The bot will also guide you on submitting your entry as a legitimate participant.

All entries must be submitted via GitHub, and your account must be at least a month old.

For comprehensive instructions on submitting your entries, refer to the official GitHub repository with the challenge tasks, which the bot will provide you on the first day of the contest.

The scoring system is simple. For each solved problem, the participant can earn a maximum of 6 points:

• Successful solution of the problem = 5 points
• Gas efficiency of the solution = 0 to 1 extra point

Prizes

The pool of $20,000 TON will be split equally between the top 100 participants of the leaderboard after plagiarising participants are removed. Every participant on the leaderboard will receive a participation soulbound token (SBT).

Prize pool distribution:

• $7,000 in TON — The top 15% of eligible participants
• $7,000 in TON — The middle 30% of eligible participants
• $6,000 in TON — The bottom 55% of eligible participants

Impressive, right? Hurry up and join!

Good luck!

Hello, Codeforces!

On Dec/19/2023 17:35 (Moscow time) the Codeforces Round 916 (Div. 3) will start. You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended 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.

You will be given 2 hours and 15 minutes to solve 6-8 problems. 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 five 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 invented and prepared by Adilbek adedalic Dalabaev, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Roman Roms Glazov, Alexander fcspartakm Frolov, and me. Also, big thanks to Vladislav Vladosiya Vlasov for his excellent coordination.

Thanks to Mike MikeMirzayanov Mirzayanov for Codeforces and Polygon systems!

And, the last but not the least, big thanks to the testers FBI, Kalashnikov and SonOfHonor for their valuable advice and suggestions!

Good luck in the contest! I hope you'll enjoy solving the problems we have prepared.

UPD: Editorial is out

Hello Codeforces!

On Dec/18/2023 17:35 (Moscow time) Educational Codeforces Round 160 (Rated for Div. 2) 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 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:

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

UPD: The editorial can be found here.

Hello, Codeforces! Or, as we like to say in Romania: Dacă voi nu mă vreți, eu vă vreu, Codeforces!

I am glad to finally invite you to participate in Codeforces Round 915 (Div. 2), which will start on Dec/16/2023 17:35 (Moscow time). You will be given 6 problems and 2 hours to solve them.

The problems were supposed to be authored and prepared by valeriu, but in reality they were by tibinyte.

I would like to thank:

• Artyom123, for his recherché coordination.

• Say_my_name for LGM testing

• cristi_tanase, Gheal, andrei_boaca,
  Andreasyan, eggag32, wavelets, Riblji_Keksic, htetgm, rolandpetrean, Lotomba, Dominater069, enigma.cpp, FairyWinx, wuhudsm for all being phenomenal testers in equal measure.

• freak93 for TBD.

• MikeMirzayanov for great platforms, codeforces and polygon!

Scoring Distribution: 500-1000-1500-2000-2250-2250

The problemsetters wish you good luck & have fun :)

Editorial is available here.

Hello!

On December 13th, the ICPC Northern Eurasia Finals (previously known as NEERC) will take place. The competition will be held at several venues: St. Petersburg, Novosibirsk, Kutaisi, and Astana. Almost 300 teams will participate in it.

We invite you to join the online mirror of the competition: 2023-2024 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred). It will start at Dec/13/2023 10:35 (Moscow time). We recommend participating in teams, but experienced individual participants will also have fun.

The duration of the competition will be 5 hours. Of course, the round is unrated.

Good luck!

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:

• Review our Kotlin solutions for the Advent of Code algorithmic puzzles.
• Read our competitive programming tutorial.
• Watch the videos from our Kotlin in Competitive Programming YouTube playlist.
• Look at the problems from the previous practice rounds.

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.

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.net/blog/entry/123261.

Note the unusual time of the round.

Hello Codeforces!

lunchbox, Apple_Method, and I are pleased to invite you to participate in Codeforces Round 914 (Div. 2) on Dec/09/2023 19:05 (Moscow time). You will be given 2 hours to solve 6 problems (and one subtask).

The round will be rated for participants of Division 2 with a rating lower than 2100.

We promise the statements will be clear and concise, suitable for AdamantChicken2 to read wink wink.

Also, we would like to thank:

• errorgorn for the epic coordination.
• Alexdat2000 for the Russian translations.
• MikeMirzayanov for the amazing Codeforces and Polygon platforms (and finally taking Polygon off beta).
• [VIP] EnDeRBeaT for testing and statement assistance.
• [Upsolver+] omeganot and TonightV for breaking our problems.
• [Upsolver+] Yuu, [Upsolver+] Andreasyan, [Upsolver+] PurpleCrayon, [Upsolver+] BucketPotato, [Upsolver+] willy108,[Upsolver] hyforces , [Upsolver] wuhudsm, [Upsolver] cry, [Upsolver] htetgm, [Upsolver] Beaboss, [Upsolver] Akksharvan, sum, BossBobster, priyanshu.p, maxrgby, and PoloniumLuke for testing the contest and providing us valuable feedback.

We hope you will enjoy the contest and receive positive delta!

Scoring distribution

$$$500 — 750 — 1000 — (1250 + 750) — 2750 — 3500$$$

UPD

The editorial has been posted!

Congratulations to our winners!

Congratulations for our first solvers!