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!

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!

Hello! Codeforces Round 913 (Div. 3) will start at Dec/05/2023 17:45 (Moscow time). 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, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

You will be given 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by 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)
• do 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.

Problems have been created and written by pashka, MikeMirzayanov and me.

Part of the problems in this round were in the Cyprus Programming Challenge. If you participated in it, please refrain from participating in this round.

We would like to thank:

1. peltorator, FairyWinx for red testing.
2. Vladithur, Valters07 for yellow testing.
3. stefanbalaz2, FBI, SlavicG, flamestorm, SashaT9, mesanu, trainerherp, Ush1su for purple testing.
4. dan_dolmatov, Yousef.Osama for blue testing.
5. Sergey140146659, Pa_sha, garysun2 for cyan testing.

Good luck!

UPD: Editorial

Hello Codeforces!

On Dec/03/2023 17:35 (Moscow time) Educational Codeforces Round 159 (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, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Roman Roms Glazov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

UPD: Editorial is out

Hello Codeforces!

We are going to hold The 2023 ICPC Asia Jakarta Regional Contest.

We invite you to join the online mirror contest 2023-2024 ICPC, Asia Jakarta Regional Contest (Online Mirror, Unrated, ICPC Rules, Teams Preferred) on Codeforces. It will be held on Dec/03/2023 07:35 (Moscow time) and will last for 5 hours.

The mirror will be held using ICPC-style scoring with 10 to 13 problems. The problem statements will only be available in English. We encourage participating as a team using only one computer for coding (as in ICPC contests). The mirror will be unrated.

Some useful links:

• The 2023 ICPC Asia Jakarta homepage
• The regional information in ICPC Global
• The onsite scoreboard

We hope that you will enjoy the contest. Good luck and have fun!

UPD. The mirror has started! You can also see the public scoreboard of the onsite contest (started 90 minutes earlier) from the provided link.

UPD2. The mirror has ended! You can find the editorial here. The onsite scoreboard will be unfrozen after the closing ceremony. Thank you for participating and we hope that you enjoyed the problemset!

Γεια σου (Hello), Codeforces once again!

Adam_GS and I are glad to invite you to participate in Codeforces Round #912 (Div. 2) which will take place on Nov/30/2023 19:35 (Moscow time). Note the unusual start time of the round. As usual, this round will be rated for participants with rating lower than 2100.

Problems were created and prepared by Adam_GS and me. We tried to make them interesting, with short and clear statements. We hope that you will enjoy them!

I would like to thank:

• ScarletS for amazing coordination of this round.

• Adam_GS for joining as an author after testing the contest.

• fishy15, Andreasyan, phattd, Murinh0, irkstepanov, wuhudsm, Ari, satyam343, Qualified, nyaruhodo, Trumling, Earlyamazon, freedommo33, jeroenodb, Nafis, czauderna, m.szeliga, Piokemon, Marky, jerzyk, jamjanek, t.kwiatkowski, AverageDiv1Enjoyer, revanth2002, htetgm, purp4ever, nor for testing the problems and providing useful feedback.

• MikeMirzayanov for Codeforces and Polygon platforms.

You will be given $$$6$$$ problems (and one subtask) and $$$2$$$ hours and $$$15$$$ minutes to solve them.

The score distribution will also be announced shortly.

Good luck and have fun!

UPD1:

Score Distribution: $$$500-1000-1500-(1500-2500)-2250-3500$$$

UPD2:

Editorial

UPD3:

Congratulations to the winners:

Div2:

1. DoIodu123

2. 69JohnMouse69

3. transfeft

4. vflower

5. Top2Greece

Div1 + 2:

1. Um_nik

2. ecnerwala

3. Ormlis

4. tourist

5. noimi

Hello, Codeforces!

Riblji_Keksic and I are glad to invite you to Codeforces Round 911 (Div. 2), which will start on Nov/26/2023 17:35 (Moscow time). You will be given 6 problems and 2 hours to solve them.

The round will be rated for participants of Division 2 with a rating lower than 2100. Division 1 participants can participate unofficially.

All problems are invented and prepared by Riblji_Keksic and me.

Special thanks go to n0sk1ll and TimDee for their great work during the testing process of the round.

And of course, I would love to thank the people who made this round possible:

• pashka for his great coordination of the round!

• IgorI for helping host the round!

• Alexdat2000 for helping translate the round!

• prvocislo, wxhtzdy, valeriu, satyam343, n0sk1ll, TimDee, wuhudsm, AlphaMale06, Blagoj, priyanshu.p, Acanikolic73, gubica, ognjentesic, VeljkoGalovic and repmann for testing the round and providing valuable feedback!

• KAN for his contribution towards the round!

• MikeMirzayanov and the team for the codeforces and polygon platforms!

• You for participating!

We hope that you will participate and enjoy the round!

Update 1: The score distribution is 500 — 1000 — 1250 — 2000 — 2250 — 3000

Update 2: Congratulations to the winners:

Div. 2:

1. TransFeftAutoV

2. vflower

3. eloge

4. Illumina

5. Im_dik

6. Gold_Record

7. Haaland

8. mban259

9. hazzler

10. 111445

All participants:

1. fallleaves07

2. turmax

3. A_G

4. ppavic

5. minato

6. Yuu

7. potato167

8. Rubikun

9. Heltion

10. emthrm

First solvers:

A. people_plus_plus in 0:01

B. A_G in 0:04

C. WLZ in 0:04

D. A_G in 0:12

E. Superposition in 0:17

F. turmax in 0:26

Update 3: Editorial

Hello, Codeforces!

We are happy to invite you to an exciting online event: 2024 New Year ICPC Challenge powered by Huawei，which will start on January 12, 2024, 15:00 (UTC+8).

In this Challenge, you will have a unique chance:

• to compete with top programmers globally
• to solve 1 exciting problem prepared by Huawei
• to win amazing prizes from Huawei!

It is an individual competition.

2024 New Year ICPC Challenge powered by Huawei:

Start: January 12, 2024, 15:00 (UTC+8)

Finish: January 26, 2024, 15:00 (UTC+8)

We hope you'll enjoy this complex yet very exciting Challenge!

Problem

We are glad to propose to you an exciting challenge “Accuracy-preserving summation algorithm”, which is prepared by Huawei Computing Product Line..

With this challenge, we focus on summation algorithms of floating point numbers in different precisions with the goal to use the lowest possible precision without losing too much of the accuracy of the end result. This problem arises in high-performance computing as lower precision can be computed faster. At the same time it also loses accuracy faster and can even lose it completely. Finding the right balance between fast low precision calculations and higher precision intermediate summations is a challenging task on modern architectures, and you would have an opportunity to try addressing this challenge.

Prizes from Huawei

Challenge Rules and Conditions

By participating in this Challenge, you agree to the Challenge Rules and Conditions of Participation

Good luck, we hope this will be fun!

Hello Codeforces,

We are very glad to invite you to participate in CodeTON Round 7 (Div. 1 + Div. 2, Rated, Prizes!), which will start on Nov/25/2023 17:50 (Moscow time). You will be given 8 problems and 2.5 hours to solve them. The round will be rated for everyone.

All the problems are written and prepared by lanhf, Mike4235, thenymphsofdelphi, xuanquang1999 and me.

We would like to give our sincere thanks to:

• errorgorn for his wonderful coordination!
• Alexdat2000 for translating problem statements.
• Um_nik and conqueror_of_tourist for Legendary Grandmaster testing.
• jeroenodb, Kuroni, dario2994 and dreamoon_love_AA for International Grandmaster testing.
• generic_placeholder_name, MofK, minhcool, dvdg6566 and magnus.hegdahl for Grandmaster testing.
• dantoh for International Master testing.
• apoorv_me, 18o3, beepbeepsheep, jamessngg, zengminghao, oolimry, iLoveIOI, pavement and jamielim for Master testing.
• Kofta, Dewi, Nahian9696, bensonlzl and Myrcella for Candidate Master testing.
• ABalobanov, AVdovin, Blagoj, teruel, xink and Antonn_114 for Expert testing.
• BeezMinh, aureg109, Yoo_Jeongyeon, Sunnyyyy and SYY for Specialist testing.
• NVGU for Pupil testing.
• vszda, tibinyte and hminh for Newbie testing.
• MikeMirzayanov for the great codeforces and polygon platform.
• You for participating in the round.

The score distribution is $$$500-1000-1500-2000-2250-2750-3250-(4000+1000)$$$.

Hope everyone can enjoy the round!

Congratulations to the winners!

1. Radewoosh
2. ksun48
3. ecnerwala
4. maroonrk
5. amiya
6. hos.lyric
7. zh0ukangyang
8. 244mhq
9. Vercingetorix
10. BigYellowDuck

Congratulations to the first solves as well!

• A: dXqwq
• B: tourist
• C: tourist
• D: tourist
• E: tourist
• F: ksun48
• G: Radewoosh
• H1: ksun48
• H2: ecnerwala

UPD1: The contest is delayed by 15 minutes due to prior issues with the registration system in order to make sure everyone is correctly registered. Please double-check that you are registered.

UPD2: Editorial

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 7.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 7 will receive valuable prizes.

The first 1,023 participants will receive prizes in TON cryptocurrency:

• 1st place: 1,024 TON
• 2–3 places: 512 TON each
• 4–7 places: 256 TON each
• 8–15 places: 128 TON each
• …
• 512–1,023 places: 2 TON each

We wish you good luck at CodeTON Round 7 and hope you enjoy the contest!