There will, and there shall be a THU round!

Nihao Codeforces! After the unfortunate event which led to Codeforces Round 1010 (Div. 1, Unrated) and Codeforces Round 1010 (Div. 2, Unrated) being unrated last week, we’re back and stronger than ever!

Tsinghua University’s Student Association of Algorithmic Competitions (THUSAAC) is pleased to invite you to participate in Codeforces Round 1012 (Div. 1) and Codeforces Round 1012 (Div. 2) on Mar/23/2025 08:35 (Moscow time). This round will be RATED for everyone. You will be given 2 hours and 30 minutes to solve 5 problems for division 1 and 6 problems for division 2, and two of each will have subtasks. Note the unusual time of the round.

Our team of amazing problem setters include: Iam1789, Ecrade_, E.Space, QuietBeautifulThoughts, gyh20, SpiritualKhorosho, dapingguo8, myee, abruce, _Lucien. Some of the problems prepared were not used in the final contest but we would still like to thank them nonetheless.

We would also like to express our gratitude to the following individuals:

• KAN for helping to host the round;

• FairyWinx for coordination and helping with the problem preparation;

• The team of problem setters for crosschecking the problems and also donghanwen, SnowySummer, wangjinbo, xiaoziyao, turmax, SomethingNew, I_love_kirill22, temporary1, LeoPro, gmusya, KiruxaLight, 18o3, mz1 for testing the contest and providing us very useful feedback;

• Tsinghua University’s administration, especially our advisor Wentao Han for helping us in all means possible to ensure the smooth organisation of the whole THUPC event;

• MikeMirzayanov for the amazing Codeforces and Polygon platform!

THUPC is an annual event hosted by Tsinghua University’s Student Association of Algorithmic Competitions. It is the largest student-run competitive programming contest in China with the top 100 Competitive Programming teams from all over China coming onsite to vie for the crown of BEST CP Team in China after qualifying from a pool of 1000+ teams.

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

UPD: Here comes the scoring distribution.

Division 1:

Division 2:

Hi Codeforces!

I Serval am glad to invite everyone to participate in Codeforces Round 1011 (Div. 2), which will be held on Mar/22/2025 17:35 (Moscow time).

This round will be rated for participants with rating lower than 2100. We will be glad to see the participants with a higher rating to take part in our round unofficially as well!

You will be given 6 problems to solve in 2 hours, one of which will be divided into two subtasks. Scoring distribution will be announced later.

I would like to thank everyone that makes this round possible:

• Error_Yuan and satyam343 for coordination of the round and help with the preparation. It is noteworthy that this round is the debut of Error_Yuan as the coordinator. Special thanks to him!
• 18o3, AG-88301, Dominater069, Edeeva, Graythron, Hanghang007, JagguBandar, LMeyling, N_z__, Nerovix, Proof_by_QED, RDDCCD, RTE, SSerxhs, SkyWave2022, SpyrosAliv, StarSilk, _istil, chromate00, darkkcyan, guangmingzhengda, larush, macaquedev, mathtsai, temporary1, tiger2005, yoru_sacri for testing the round and providing valuable feedbacks.
• Alexdat2000 for Russian translations of the problemset.
• MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• You, for participating in the round and gaining a positive delta.

Good luck & Have fun! (∠・ω < )⌒☆

UPD: Scoring distribution: 500 — 1250 — 1250 — 1750 — 2500 — (2000 + 1000).

UPD2: Editorial is out. Congratulations to the winners!

Div. 2:

1. sounansya
2. DuyNgaDocTon1410
3. SoloRejudger
4. nocap
5. Asbjorn

Div. 1 + Div. 2:

1. potato167
2. A_G
3. arvindf232
4. antontrygubO_o
5. TKT_YI

Hello, Codeforces.

The XIII BSUIR Open Programming Championship will be held from March 17 to May 3, 2025 (Minsk, Belarus).

Registration is already open and available until March 20 (inclusive). Teams consisting of 3 students from one higher educational institution, as well as school teams from different educational institutions are allowed to participate. Registration is made by the team captain on the website acm.bsuir.by.

The competition will be held in several stages:

• March 17 — 24 — Qualifying round (in absentia, mandatory for schoolchildren and students of BSUIR)
• April 9, 14:00-19:00 — Semi-final (in person, at sites organized by educational institutions)
• April 26 — Student final (in person, Minsk, BSUIR, Building 4, 9 Gikalo Street)
• May 3 — School final (in person, Minsk, BSUIR, Building 4, 9 Gikalo Street)

More information about the upcoming Olympiad and registration can be found on the website acm.bsuir.by.

Some previous videos:

• BSUIR Open XII Student 2024
• BSUIR Open XI Junior 2023
• BSUIR Open X Student 2022

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos.

On Mar/17/2025 17:35 (Moscow time) Educational Codeforces Round 176 (Rated for Div. 2) will start.

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, Alex fcspartakm Frolov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Neapolis University Pafos also have a message for you:

Admission to the Computer Science and Artificial Intelligence bachelor's program at Neapolis University Pafos is open!

The JetBrains Foundation supports this bachelor's program and offers 15 fully funded scholarships for the most talented applicants. The scholarships cover tuition, accommodation, medical insurance, visa fees, and pocket money (€300 per month).

First admission round:

• Application deadline – April 23, 2025
• Entrance test – April 27, 2025

UPD: Editorial is out

Nihao! Hello to all fans of competitive programming and Codeforces enjoyers!

On behalf of Tsinghua University’s Zhili College, we — your proud and slightly sleep-deprived Class of 2028 Information and Computing Science students — are happy to invite you to participate in Codeforces Round 1010 (Div. 1, Unrated) and Codeforces Round 1010 (Div. 2, Unrated), which will take place on Mar/15/2025 17:35 (Moscow time). Note the unusual start time of the round.

You’ll have 3 hours to tackle 7 problems for division 1 and 6 problems for division 2, the round will be rated for all participants. It’s a little longer than your typical Codeforces round, and yes, we know you’ll be sleep-deprived — but who needs sleep when there’s coding to do, right?

This round’s problems are brought to you by the incredible Ecrade_, newbiewzs, chen_03, 18Michael and sunzh. Special thank you to dapingguo8, Zesty_Fox and Iam1789 who also prepared problems that were ultimately not used in this round.

A massive THANK YOU to the following legends who made this event possible:

• The one and only KAN for his invaluable support in hosting the round.

• Our chad coordinator, FairyWinx for coordinating this round, finding testers, and providing moral and technical support.

• Our brilliant testers: Zesty_Fox, peiwenjun, Iam1789, chen_03, wangjinbo, sunzh, exxqfu, li0201. peop1e_, I_love_kirill22, RP-1, TeaTime, turmax for testing and providing invaluable feedback.

• Our fantastic organisers: HeziCyan, Iam1789, cszyf, and KaiSuoShuTong for the smooth operation of the contest.

• Our advisors zhou888, RegisterName, Yijie Wang and Xi Wang from Zhili College for supporting our efforts and ensuring school approval.

• Big shoutout to DreamingRabbit, president of Tsinghua University’s Association of Algorithmic Competitions, for his steadfast support and unwavering determination in helping us turn this dream into a reality.

• MikeMirzayanov and geranazavr555 for enabling this event through the amazing Codeforces platform.

Zhili Cup itself is an annual event hosted by Tsinghua University’s Zhili College along with its freshmen of ICS. We are delighted to meet you on Codeforces this year.

Good luck, and may your code be bug-free and your coffee cup never empty.

See you at the round!

UPD: Here comes the scoring distribution.

Division 1:

Division 2:

UPD2: Due to technical problems, the round is postponed for 30 minutes.

UPD3: The round is postponed to the usual Codeforces time and won't be rated. We (Codeforces team) apologize for these problems.

UPD4: Contest is over! Thank you to everyone who participated in the round even though it is unrated, we truly hope that you all enjoyed our problems and had a great time participating. The editorials will be a bit delayed but we promise they'll be here soon! See you guys again soon!

UPD5: Editorial

Oh hello there. This is chromate00, just casually on the announcement of Codeforces Round 1009 (Div. 3). And now, you see a drawing.

$$$\square$$$ — $$$\triangle$$$ — $$$\triangle$$$ — ◯ — $$$\triangle$$$ — $$$\square$$$ — $$$\triangle$$$

And then, you think. You see a square, a triangle, and a circle. Also, a Korean problemsetter. You immediately imagine the certain survival game that popped up in your memory. And you may be right. Or you might be wrong. Whatever, what I can ensure you is that you will be absolutely stunned to see the problems. Or astonished. You might not believe what you see. This round might change everything.

Anyways, the preface was a bit too long. Starting from Mar/11/2025 17:35 (Moscow time), you will be given $$$\mathbf{7}$$$ problems to be solved in $$$\mathbf{2.5}$$$ hours. There is at least one interactive problem, so I strongly urge you to read the guide if you are unfamiliar with the format.

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.

Remind yourself 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)
• 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).

Also, note the (relatively recent) rule restricting the use of AI. If you are caught while breaking this rule, you will be terminated.

This round is made possible by the help of the following people:

• cry and Vladosiya for coordinating the round (and translating the statements),
• Proof_by_QED for reviewing the tasks (and not so particularly testing them),
• Our army of (not so) pink soldiers: Intellegent, amoeba4, mathtsai, Error_Yuan, temporary1, Edeeva, yeetholmes619, hashman, larush, poi, (VIP) Dominater069, (VIP) LMeyling, (VIP-) macaquedev, antontrygubO_o, Mercuria, DivinePunishment, 0pt1mus23, pianapolataa, reirugan, efishel, (VIP) awesomeguy856, rewhile, __baozii__, yoru_sacri, -firefly-, sbreger60, monadtransformer, Rahuldeb5,
• The VVVIP, MikeMirzayanov, for great platforms Codeforces and Polygon.

I hope that you will also be in the spectacular moment.

UPD: Editorial has been posted.

UPD2: Congratulations to the top participants definitely except for the ones who cheated their way out!

All participants:

1. ksun48
2. arvindf232
3. StarSilk
4. maspy
5. risujiroh

Trusted (rated) participants:

1. sharvil_cpp
2. Xing_Kong_C......has been terminated
3. jxu
4. 1zaid1
5. eysikingE
6. I_am_the_Lowest
7. ConvexHulllllll

Hello, Codeforces!

I'm glad to invite everyone to Codeforces Round 1008 (Div. 1), Codeforces Round 1008 (Div. 2), which will be held on Mar/10/2025 17:45 (Moscow time).

You will be offered $$$7$$$ problems in both divisions 1 and 2, and you will be given $$$2$$$ hours and $$$30$$$ minutes to solve them.

Both divisions contain at least one interactive problem(s). Please look up the guide if you are unfamiliar with them.

I'd like to give my utmost thanks to

• satyam343 and Kaey for coordinating this contest, preparing statements/tasks, and donating a problem.

• The testers: Dominater069, LMeyling, Rhael, Mysticmage45, tigerBoss101, Non-origination, TyroWhizz, _istil, LipArcanjo, Error_Yuan, Proof_by_QED, ffao, NerfThis, ikrpprppp, Murinho, WLZ, Irmuun.Ch, Tainel, Chaska, marianoferesin, ankan2526, Darshan_Bhangale, kolomig0r, dougalves, profchi, Lucina, 0I0acOJleHbKa, Marckess, Saman., N_z__, PeruvianCartel, sammyuri, A_G, catology, arvindf232

• My friends Rhael for an illustration, Punpun (no CF account) for one task, and a shoutout to Mysticmage45 for no particular reason.

• Alexdat2000 for the Russian translation.

• MikeMirzayanov for Polygon and Codeforces platforms.

I hope everyone will indulge in the tasks blissfully.

Score distribution

Division 1: $$$500-1000-1500-2250-2250-2500-3000$$$

Division 2: $$$500-750-1250-1750-2000-2750-3500$$$

Congratulations to the winners!

Division 1

1. jiangly

2. Ormlis

3. Um_nik

4. tourist

5. ksun48

Division 2

1. a1048576

2. SussykinWantsNatalia

3. DanielAnker

4. Manasvi

5. hungpc1577

Editorial

Welcome to the final weekend of Codeforces Blitz Cup! More information about selection matches is available in this post, but we are now down to just 16 contestants! Here is how they will compete on Saturday and Sunday for the content and glory!

Saturday, March 8

1. turmax 25 : 20 b6e0: Mar/08/2025 13:00 (Moscow time) Scoreboard
2. errorgorn 31 : 2 izban: Mar/08/2025 14:10 (Moscow time) Scoreboard
3. isaf27 2 : 31 alireza_kaviani: Mar/08/2025 15:00 (Moscow time) Scoreboard
4. winners of 1 and 2: errorgorn 20 : 25 turmax: Mar/08/2025 16:00 (Moscow time) Scoreboard
5. Geothermal 35 : 10 jonathanirvings: Mar/08/2025 17:00 (Moscow time) Scoreboard
   ☕

6. heuristica 0 : 33 antontrygubO_o: Mar/08/2025 19:00 (Moscow time) Scoreboard

7. tourist 31 : 2 conqueror_of_tourist: Mar/08/2025 20:00 (Moscow time) Scoreboard
8. ksun48 20 : 13 Kuroni: Mar/08/2025 21:00 (Moscow time) Scoreboard
9. winners of 6 and 7: tourist 45 : 0 antontrygubO_o: Mar/08/2025 22:00 (Moscow time) Scoreboard
10. Golovanov399 33 : 0 induk_v_tsiane: Mar/08/2025 23:00 (Moscow time) Scoreboard

Sunday, March 9

• 11: winner of 3 and 5: alireza_kaviani 10 : 35 Geothermal: Mar/09/2025 15:00 (Moscow time) Scoreboard
• 12: winner of 8 and 10: ksun48 15 : 18 Golovanov399: Mar/09/2025 16:00 (Moscow time) Scoreboard
• 13: Semifinal: winner of 4 and 11: turmax 12 : 21 Geothermal: Mar/09/2025 17:00 (Moscow time) Scoreboard
• 14: Semifinal: winner of 9 and 12: tourist vs Golovanov399: Mar/09/2025 18:00 (Moscow time) Scoreboard Scoreboard2
• 14 rematch: tourist 27 : 18 Golovanov399: Mar/09/2025 19:20 (Moscow time) Scoreboard
• 15: Final match: winner of 13 and 14: tourist 45 : 0 Geothermal: Mar/09/2025 20:05 (Moscow time) Scoreboard

And the winner is

Congratulations tourist on winning the Blitz Cup 2025!

And huge thanks to lperovskaya, Vladosiya, tourist, MikeMirzayanov for organizing the event, as well as Egor and jonathanirvings for commentating most of the matches!

Tune into the live broadcast on youtube.com/@codeforceslive to see your favorite contestants compete and commentate!

Hello everyone!

Soon, the Open Olympiad in Informatics will take place, which you may know from the online mirror of last year or from the rounds 345, 469, 545, 626, 707, 775. This olympiad is prepared by Moscow Olympiad Scientific Committee. Archives from previous years, problems from qualifying stages, and other information can be found on the olympiad website inf-open.ru.

The Open Olympiad consists of interesting and difficult problems proposed by our authors' team. Therefore, we decided to conduct a non-rating mirror of the Olympiad on Codeforces. The Olympiad takes place in two rounds, each consisting of 4 problems, not ordered by difficulty, and 5 hours to solve them. The difficulty of the problems is comparable to the level of Div. 1. Each problem is worth 100 points that are distributed into multiple subtasks with different constraints that allow the participant to earn partial score. Testing is done in the IOI format, where the participant receives a full testing report on all tests in the Online-subtasks during the competition. The feature of the Open Olympiad is that some problems have Offline-subtasks, the results of which will only be available after the end of the competition. Note, that you will not have access to the scoreboard during the competition.

The mirror on Codeforces will take place in Mar/07/2025 11:05 (Moscow time) and Mar/10/2025 11:05 (Moscow time).

The competition problems were created and prepared by Kapt, allvik66, stepanov.aa, Mangooste, AgafonovArtem, dyrbulshchyl, RP-1, valerikk, yunetive29, Kniaz, Alexdat2000 guided by Mangooste, grphil and Helen Andreeva. Special thanks to Tikhon228 for his contribution to the preparation of the problems.

Special thanks to MikeMirzayanov for the codeforces and polygon systems, which were used in preparing the problems for this Olympiad.

Many thanks to the Olympiad testers: Ormlis, isaf27, allvik66, AgafonovArtem, RP-1, Qwerty1232, kostylevGO, katyaporay, FairyWinx, a.stepanov281005, EgorUlin, pakhomovee, ArtAlex, Sweezy, Be_dos, valerikk, alexsushin, Dart-Xeyter, yunetive29, AndreyPavlov, Mikhango, v0s7er.

Good luck!

UPD1: The results of the first day are available.