Hello, Codeforces!

We are happy to invite you to an exciting online event: ICPC Online Challenge powered by Huawei.

This Challenge features the problem

Scheduling Algorithm for Collaborative Inference System With the rapid advancement of artificial intelligence, large language model (LLM) services are becoming increasingly integrated into people’s daily lives and work. At the same time, the economic efficiency and data security of these services are receiving greater attention.

Edge-Cloud Collaborative Inference has emerged as a promising approach to addressing these challenges. In this architecture, LLM inference is divided between a user’s on-premises edge environment and the cloud. Using a U-shaped split, the first and last layers of the model run on the edge, while the computationally intensive middle layers run in the cloud. This allows private inputs and outputs to remain on the user’s side while cloud resources are used for the heavier computation.

However, this architecture requires repeated interaction between the edge and the cloud during both the prefill and decoding stages. When requests are processed sequentially, these interactions can create “bubbles”—periods in which computing resources remain idle while waiting for other parts of the system.

Your challenge is to design a concurrent scheduling strategy that:

• maximizes overall system throughput; and
• ensures that every request satisfies its latency Service Level Objective (SLO).

Participants will need to carefully coordinate computation and communication across the edge and cloud while balancing throughput and per-request latency requirements.

We hope you will enjoy this challenging optimization problem inspired by real-world AI infrastructure.

Start: August 14, 2026 11:00 UTC (UTC+0)

Finish: August 28, 2026 10:59 UTC (UTC+0)

Prizes

By participating in this Challenge, you agree to the official Rules.

The use of AI tools, including generative AI and AI-assisted coding tools, is permitted during the Challenge. Participants remain fully responsible for the correctness, originality, and compliance of their submissions with all applicable rules.

To be eligible for a prize, you must register through: https://icpc.global/regionals/finder/ICPC-Online-Challenge-2026.

If you cannot access the rules document, please contact [email protected].

Good luck, and we hope you enjoy this complex yet exciting Challenge!

Hello, Codeforces!

We are glad to invite you to participate in Codeforces Round 1116 (Div. 1) and Codeforces Round 1116 (Div. 2) on Aug/09/2026 17:35 (Moscow time).

The round will be rated for participants from both divisions. You will be given 6 problems and 2 hours and 30 minutes to solve them. At least one of the problems will be divided into subtasks.

Please note that this contest contains at least one run-twice (communication) problem. Please read the guides for run-twice problems before the contest if you are unfamiliar with them.

All problems were authored and prepared by Error_Yuan and me, paulzrm.

More than eight years after Codeforces Round 449, Chtholly Nota Seniorious — the happiest girl in the world — is returning to Codeforces!

In this round, you will once again meet Chtholly, Nephren, Ithea, Willem, and other characters from What Do You Do at the End of the World? Are You Busy? Will You Save Us?, and help them overcome a new series of challenges.

We would like to thank:

• Error_Yuan for his excellent coordination, patient guidance, and invaluable help throughout the preparation of the round.

• Alexdat2000 for translating the statements to Russian.

• HugeWide, my teammate, for VIP testing and for all his help throughout the preparation of the round.

• HHH666666, XG0000, Mitsukasa_Ayase, zt17, a_little_cute, aaa_Pigeon2, StarSilk, tiger2005, Proof_by_QED, _istil, nifeshe, floptron1, arvindr9 and WorldWarV for testing the round and providing valuable feedback.

• KAN and MikeMirzayanov for the great Codeforces and Polygon platforms.

• You

  for participating in this round.

The scoring distribution will be announced later.

We hope you enjoy the problems and Chtholly’s story.

Good luck and have fun!

UPD1: The Scoring distribution is:

• Div. 1: 500 — 1000 — 1750 — 1750 — (1750 + 1250) — 3500
• Div. 2: 500 — 1000 — 1500 — 2000 — 2750 — 3000

UPD2: The editorial is out.

UPD3: Congratulations to the winners!

Div. 1 (subject to change):

1. turmax
2. noimi
3. Asakizz
4. gzyo4
5. StevenKnight

Div. 2 (subject to change):

1. lvsedeqinglvse
2. Cucumber0721
3. Smarth_coder
4. asterunee
5. Chth_kitten

We would also like to congratulate the first solvers of each problem (subject to change):

1. Div. 2 A: Forestmy17 00:01
2. Div. 2 B: asterunee 00:04
3. Div. 1 A / Div. 2 C: A_G 00:02
4. Div. 1 B / Div. 2 D: maspy 00:05
5. Div. 1 C / Div. 2 E: literalchild 00:19
6. Div. 1 D / Div. 2 F: de1uxegg 00:23
7. Div. 1 E1: __baozii__ 01:02
8. Div. 1 E2: ABCaCaCa_ 01:10
9. Div. 1 F: turmax 01:34

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos. They offer a BSc in Computer Science and AI with JetBrains Scholarships. Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Limited scholarships available — don't miss your chance to study in Europe for free!

Educational Codeforces Round 193 (Rated for Div. 2) will start on Aug/07/2026 17:35 (Moscow time).

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 problems and 2 hours to solve them.

The problems were proposed and prepared by Maxim FelixArg Novotochinov and me.

Huge thanks to Mike MikeMirzayanov Mirzayanov, the creator of Codeforces and Polygon — two great competitive programming platforms. Without them, the Educational Rounds would be impossible.

Also, big shoutout to round testers: awoo, Alenochka, pusheen_1024, savolay, yegor.l!

We wish you good luck in the contest!

upd: The editorial can be found here.

Hello, Codeforces!

We are excited to invite you to participate in Codeforces Round 1115 (Div. 2), which will take place on Aug/06/2026 17:35 (Moscow time).

The round will be rated for all participants with a rating below 2100. Participants from Division 1 are warmly welcome to participate unofficially.

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

The round was prepared by TomitaMatei and me, Bufu.

We would like to express our deepest gratitude to everyone who made this round possible:

• cry for their excellent coordination and infinite patience while reviewing the problems!

• Alexdat2000 for translating the statements to Russian.

• Um_nik and KAN for pre-reviewing the round!

• Our wonderful team of testers for solving the problems and providing highly valuable feedback: Intellegent, awesomeguy856, _istil, andrei_n, Friedrich, __baozii__, simplelife, omsincoconut, madlogic, nik_exists, Edeeva, SpyrosAliv, and Argentum47.

• MikeMirzayanov and KAN for creating and maintaining the amazing Codeforces and Polygon platforms!

• You for participating in the round!

The score distribution will be:

$$$500$$$ — $$$1000$$$ — $$$1250$$$ — $$$1750$$$ — $$$2250$$$ — $$$2750$$$

Good luck, have fun, and may the rating be with you!

UPD: Congratulations to the winners!

Unofficial participants:

1. abc864197532

2. Rubikun

3. maspy

4. CryptoQuant

5. Lynkcat

Official participants: (subject to change)

1. Kodik

2. sahajoydeep467

3. Wonter

4. jeduardobras

5. Gemini17

UPD 2: The editorial is now available!

Hello, Codeforces!

I am very excited to invite you to participate in Codeforces Round 1114 (Div. 3), which will take place on Aug/04/2026 17:35 (Moscow time). You will be given $$$2$$$ hours and $$$15$$$ minutes to solve $$$7$$$ problems, where one problem will be split into subtasks. All problems were authored and prepared by me.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of 10 minutes for each wrong submission, following the rules of educational rounds.

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 rating of 1900 or higher at any moment in time.

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 (unless you register unrated).

I would like to thank the following people for making this round possible:

• cry for coordinating the round;
• __baozii__ for red testing;
• temporary1, Proof_by_QED for orange testing;
• SpyrosAliv, Argentum47, Friedrich, omsincoconut, wakanda-forever, reirugan, cgmoreda for purple testing;
• DivinePunishment, Mousa, Wageeh, wuhudsm, chromate00, detective...dots, Borhom for blue testing;
• Mr_Bald, ALnQ417 for cyan testing;
• Vladosiya for statement translation and testing;
• MikeMirzayanov for developing Codeforces and Polygon.

Good luck, and most importantly, have fun!

Update: Tutorial

Hello / 你好，Codeforces, ₍^. .^₎⟆

We are happy to invite you to participate in Codeforces Round 1113 (Div. 2), which will be held on Aug/01/2026 17:35 (Moscow time). This round will be rated for all participants with rating below 2100. You will be given 2 hours and 30 minutes to solve 7 problems. The tasks are authored and prepared by Zxc200611, Suwan, FISHER_ and me, szdytom.

We are extremely grateful to these wonderful people:

• satyam343 for their patient and helpful coordination.
• Alexdat2000 for translating the statements to Russian.
• Our testers: ConstructibleNumber, FetFot, liaoz123, Rvess, shorya1835, Jose_17, samsoom, AryRDW, fuad720, Pie_TealCompressorDragon, 3atori, i-love-ayase-momo, Arpa, stevvven, ALnQ417, murder_drones, SpyrosAliv, Proof_by_QED, ez_lcw, omsincoconut, A_G, _istil, chromate00, Intellegent, CSQ31, LipArcanjo, Zxx200611, MridulAhi, wuhudsm, dumb_boi, nifeshe, maomao90, avi0000, Non-origination, bitset, and gsn531.
• KAN and MikeMirzayanov for Codeforces and Polygon systems.

Score distribution: $$$500-1250-1500-1750-2500-2500-3500$$$

We sincerely hope that you will enjoy the problems!

UPD: The Editorial is out!

UPD: Congratulations to the winners!

Unofficial participants:

1. jeroenodb
2. 244mhq
3. Geothermal
4. StarSilk
5. kotatsugame

Official participants: (subject to change)

1. tuanha
2. goldenutu
3. ising36hz
4. wtzakioi
5. kylin0610

Hello / 你好，Codeforces!

We are really excited to invite you to participate in Codeforces Round 1112 (Div. 1) and Codeforces Round 1112 (Div. 2), which will be held on Jul/26/2026 17:35 (Moscow time).

For both division 1 and division 2, you will be given 2.5 hours to solve 6 problems in each division.

The problems were authored and prepared by aaa_Pigeon2, _MCYYDS_, 131241, Oken, and jhvjh.

We would really like to thank the following people for making this round possible:

• Error_Yuan for the great coordination.
• _istil and ukbwyx for optimizing some details of problems.
• tiger2005, StarSilk for black red testing.
• RockyYue, WangYuanyi, _istil, Portulaca, jason_sun, wangmarui, N_z__ for red testing.
• Watersphere, zac2010, _luqyou_, ukbwyx, cdx123456, Arpa, a_little_cute for orange testing.
• yllls, Fa_Nanf1204 for purple testing.
• 1234567890regis, qym110809, wusixuan for blue testing.
• ini_____ for green testing.
• MikeMirzayanov and KAN for the great Codeforces and Polygon platforms.
• You for participating in this round.

The score distribution is as follows:

• Div. 1: $$$750 - 1250 - 1750 - 2250 - (2250 + 1750) - 3500$$$
• Div. 2: $$$500 - 750 - 1500 - 2000 - 2500 - 3000$$$

UPD: Editorial

UPD2: Congratulations to the winners!

Div .1:

1. Benq

2. Kevin114514

3. d11maan

4. Lynkcat

5. 300iq

Div .2:

1. Math_Tereegor

2. RIMAMIR

3. MINHTPC

4. L1064

5. axoIotl

Hello Codeforces,

I'm so excited to invite you to participate in Codeforces Round 1111 (Div. 2), which will be held on Jul/18/2026 17:35 (Moscow time)!

You will be given $$$6$$$ problems to solve, one of which will be divided into subtasks. The problems were authored by me, makrav, and PvPro.

The contest was prepared by two IOI 2026 participants from Russia, so you can be sure that the problems are of the highest possible quality.

I would like to thank these people for making the contest possible:

• PvPro for coming up with an enormous number of problems for this round (and having most of them rejected by me).
• nifeshe for outstanding coordination and helping with problem preparation.
• Um_nik for preliminary reviewing the round.
• Intellegent, dinohaur, DizzyGroovy for being the first, second and third coolest testers respectively.
• allvik66, __baozii__, _istil, Wansur, TeaTime, Noobish_Monk for VIP testing.
• The rest of our testers: Mark_Pr, temporary1, Proof_by_QED, Arpa, omsincoconut, shorya1835, Argentum47, simplelife, naneosmic, nik_exists.
• MikeMirzayanov and KAN for the Codeforces and Polygon platforms.
• And You for participating!

The score distribution is as follows: $$$500 \ — \ 750 \ — \ 1250 \ — \ (1500 \ + \ 1250) \ — \ 3000 \ — \ 3500$$$

UPD: Editorial

Congratulations to the winners:

Unofficial participants:

1. potato167

2. peti1234

3. maspy

4. golomb

5. lnsuyn

Official participants: (subject to change)

1. zhenja

2. phantomas

3. AbdullahIshfaq_

4. n685

5. menborong

First solves (subject to change)
A. 00:01:14 by sivi_21
B. 00:03:32 by sevlll777
C. 00:05:38 by AshikeRuet
D1. 00:03:09 by HugeWide
D2. 00:20:32 by potato167
E. 00:29:55 by soumya_ranjan17
F. 00:46:05 by SleeplessSouris

Hello Codeforces!

I am glad to invite you to participate in Spectral::Cup 2026 Round 3 (Codeforces Round 1110, Div. 1 + Div. 2), which will start on Jul/16/2026 17:45 (Moscow time). You will be given 2 hours and 30 minutes to solve 8 problems, where one problem will be split into subtasks. Also, there is at least one interactive problem, so you are recommended to read the guide to interactive problems if you have not encountered them before.

Note that hacks will be disabled for problems A to D.

All problems are authored and prepared by myself.

Note the rule restricting the use of AI. If you are caught breaking this rule, you will be thrown into SSerxhs's basement. For your own well-being, I suggest adhering to the rules.

I would like to thank the following people for helping make this round possible!

• SSerxhs for his/her satisfactory coordination.
• Alexdat2000 for translating the statements to Russian.
• nifeshe for "I will solve this problem today" — nifeshe.
• StarSilk, EvenImage, tiger2005 for nutella testing.
• zeemanz, 0.1w33hw3, nifeshe, _istil, SATSKY_2025target_LGM for red testing.
• Seele_H, Proof_by_QED, GUAIKATTO, CReatiQ for orange testing.
• -WIDA-, Liang_SYEA, Argentum47, wakanda-forever for purple testing.
• fr200110217102, simplelife, XiaoXia, acmtoohard, big-mktx for blue testing.
• yuki_Ishijo for cyan testing.
• Whalica for green testing.
• MikeMirzayanov and KAN for the incredible Codeforces and Polygon platforms.

Score distribution:

update:

Tutorial has been published: tutorial

Now a few words from our sponsor.

🏁The final round of Spectral::Cup 2026 is coming!

This round is special to us. Not only will it conclude our three-round Spectral::Cup tournament, but it will also take place during our company’s birthday month — Spectral::Technologies turned 7 this July 🎉

Round 3 is the final part of our birthday celebration. The rest is in this video 😄

Hello, Codeforces!

Codeforces Round 1109 (Div. 3) will start at Jul/14/2026 17:35 (Moscow time). You will be offered 7 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. After open hacks all accepted solutions will be rejudged on successful hacks.

You will be given 7 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 itz_pabloo.

We would like to thank:

1. MikeMirzayanov for Polygon and Codeforces platforms.

2. Vladosiya for the excellent coordination.

3. Friendiks and Nickir for their help in preparing the problems.

4. k1r1t0, lewc, FairyWinx, zwezdinv for red testing.

5. Sokol080808, cry, AI-qv4rk, KotlechkovEgor, Fakewave for yellow testing.

6. SapeginIgor, dvb1r, VitaliiV, Gutark, feblokas, _liravel_, kaferius_cf for purple testing.

7. Maria_Chudinova, Yassia, Wileyne, Algolagon, veliak, eyfxrby, sanya37y, opa, Neckt00 for blue testing.

8. misha.arkhipov, s28b_shagabutdinov, Sava_is, nikk128, k_Teleport for cyan testing.

9. sovenok1, HelloFromMars for green testing.

10. mlovbnee for grey testing.

Good luck!

UPD: Editorial is out!