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By adamant, 24 hours ago, In English

Hi everyone!

Supported by

We are very happy to announce that Osijek camp is back this Winter, on February 15-23, 2025, right before the 2025 ICPC Europe Championship on February 28 — March 2, 2025. The camp is hosted by the School of Applied Mathematics and Computer Science of the University of Osijek and is brought to you by the organizing team of adamant and -is-this-fft-.

The camp is inspired by various competitive programming camps that we attended during our active years in ICPC, and is aimed to help college students prepare for ICPC regional contests and finals. The camp will consist of 7 ICPC-style contests and 2 days off.

Details

If you're participating in ICPC APAC, or are close to Singapore, please consider the Singapore mirror organized by errorgorn.

After some discussions with participants, and also thanks to the continued support of our sponsors, we decided to reform the structure of participation fees for the camp. While previously, participation fees were 100€ and 150€ per participant for online and onsite participation correspondingly, in this camp the participation fee for both online and onsite participants is 201€ per team.

For a full 3-person team, this marks a 33% reduction in the price of online participation, and a 55% reduction in the price of onsite participation! We hope that it will help us to incentivize onsite participation, and also participation in full teams, to make sure that it is as close as possible to the intended ICPC contest experience for everyone involved.

Note that, similar to previous camp editions, the fee does not include regular meals, travel or accommodation. Some further details about location, travel and food options can be found on the website.

We support and empathize with those affected by the ongoing war in Ukraine, therefore we offer a free participation for affected individuals and teams affiliated with Ukrainian institutions.

The expected starting time for the contests is 10am CET. For online participants, it is still a preferred starting time, but we will make accommodations for virtual participation at a later time, when necessary.

Most of our contests are originally developed for the camp. A small number of contests may be based on previous contests that have not been released to the general public. If you have seen some problems of a contest before, you can't participate on that day. We will privately contact participants who might be affected.

After the camp, we will have a silence period during which camp materials will not be released to the public. We ask participants not to discuss the problems in public unless they obtained an explicit permission from contest authors.

If you would like to get a feel of the contests, you can find links to some of the previously published camp contests here.

Participants

If you are interested in participating, please fill the form here.

We ask you to register before February 8 if you want to participate online and before February 1 if you want to participate onsite. If you require a visa, please register as soon as possible, as it might take a few weeks to receive (depending on location).

Also, if your university or organization has a lively ICPC community that may be interested in attending the camp, and you have some contacts of people in charge (e.g. coaches) we would highly appreciate if you could share some details in a direct message to me. Thanks!

Problemsetters

We'd like to thank and praise the authors of the contests in the camp:

  • Yarema, PetroTarnavskyi, mshcherba — a team from Ivan Franko National University of Lviv, who participated in the 47-th (Luxor, Egypt) and the 48-th (Astana, Kazakhstan) ICPC World Finals.
  • ntherner — Codeforces (ex?)grandmaster, IOI 2024 gold medalist, author of under 15 competitive programming problems.
  • tibinyte2006 — Codeforces newbie, ex-Codeforces pupil.
  • AmirrzwM — ICPC 2024 World Finalist, Author of Codeforces Global Round 23 and Rayan Selection Round, Iranian National Olympiad in Informatics (INOI) Silver Medalist.
  • MohammadParsaElahimanesh — Main Author of Codeforces Global Round 23 and Rayan Selection Round, INOI Silver Medalist. Best problem solver on Quera.
  • Halzion — ICPC 2023 world finalist.
  • Claris — ICPC 2017 and 2018 world finalist. Top contributor of QOJ.
  • ToniB — IOI 2023 bronze medal and CERC 2024 first place.
  • ppavic — triple IOI gold medalist.
  • dorijanlendvaj — double IOI gold medalist, Codeforces Legendary Grandmaster.
  • Pyqe — IOI gold medalist, author of IOI 2024 Nile and Tree.
  • Kinon — IMO bronze, silver, and gold medalist.

... And others. We would also like to thank errorgorn and Um_nik for their help with reviewing problem proposals. You can find more details about contest rules and technical setup on the website.

Special thanks

Finally, we say special thanks to

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By I_love_kirill22, 2 days ago, translation, In English

Hello to all fans of competitive programming and Codeforces enjoyers! We're happy to invite you to participate in Hello 2025, which will take place on Jan/04/2025 17:35 (Moscow time).

We, I_love_kirill22, dope, and induk_v_tsiane, have prepared 8 problems for you, and you’ll have 2 hours and 30 minutes to solve them. One of the problems is divided into 2 subtasks. The round will be rated for all participants.

Huge thanks to MikeMirzayanov, geranazavr555, and KAN for great systems Polygon and Codeforces!

Special thanks also go to:

Score distribution: 500 — 1000 — 1500 — 2250 — (1000+2000) — 3500 — 3750 — 4500

UPD (Update!) (Update! Yey!) Editorial — link

This round was prepared with the support of T-Generation. If you are a Russian-speaking student, please switch to the Russian version of this blog. There you will find information about our educational projects that may be interesting for you.

UPDATE

Congratulations to the winners:

  1. jiangly

  2. ksun48

  3. ugly2333

  4. Flamire

  5. Ormlis

  6. hos.lyric

  7. ecnerwala

  8. noimi

  9. maspy

  10. arvindf232

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Announcement of Hello 2025
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By MikeMirzayanov, history, 6 days ago, translation, In English

Hello, Codeforces!

Only a couple of days remain until 2025. To wrap up the year, I'm bringing an update — I hope you'll find it useful.

Now, you can automatically find and add random problems for your mashup based on a range of criteria and restrictions. The problems are sourced from the archive, and unusual problems are automatically excluded.

So, click the "Add random problems" link under the problem list and proceed to the addition form.

Here's what you can do:

  • Exclude problems that registered mashup participants have solved/attempted/authored (a problem will be excluded if at least one registered participant is familiar with it),
  • If the mashup belongs to a group (e.g., your training group), exclude all problems from other contests in that group,
  • Exclude problems with subtasks — such problems are often interconnected or reference each other,
  • Simply specify a list of handles or user lists for whom familiar problems should be excluded,
  • And finally, the most advanced option: in the "Problem Requirements" field, you can specify requirements for the problems to be added in a special format.

The "Problem Requirements" field describes the number and properties of the problems you want to find. By clicking the question mark icon, you'll see the following explanatory text.

Enter one or more lines. Each line specifies requirements for a single problem. A line must start with the Latin letter p, followed by a space, and then additional parameters can be specified:

  • Short problem name (its letter in the contest);
  • Problem difficulty requirements (e.g., ratings:1000-1200, ratings:2000, ratings:3000-, or ratings:-1000: leaving the number on the left or right of the hyphen empty means the corresponding boundary is not set);
  • Tags (use tags: and provide a comma-separated list of tags, e.g., tags:dp, binary search, brute force): a problem containing at least one tag from the list will be selected.

Examples of requirement lines:

  • "p": any problem, the letter in the contest will be assigned automatically;
  • "p F": any problem assigned the letter F;
  • "p ratings:2000-2400": a problem with a difficulty level between 2000 and 2400, with the contest letter assigned automatically;
  • "p D ratings:-1200 tags:greedy,dp": a problem with a difficulty level of no more than 1200, containing the tag dp or greedy (or both), assigned the letter D.

When you click the "Find Problems" button, you'll be presented with a list of problems to add. You can press the button repeatedly to generate different lists. In this list, you can mark the problems you like and finally add them to your mashup.

Note that next to the "Find Problems" button, after pressing it, additional statistics will be displayed. These can help you navigate the ratings of available problems under the specified restrictions.

I hope this makes finding problems for your training sessions and competitions easier.

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By Cocoly1990, 13 days ago, In English

Good... yes, good afternoon, Codeforces!

We are glad to invite you to take part in Good Bye 2024: 2025 is NEAR, which will start on Dec/28/2024 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.

All the problems are authored by _istil and me.

In this round, we would like to say goodbye to the past bad memories. However, the point is we won't say goodbye to:

UPD: The score distribution is 5001000125017502000250042504500(3000+2000).

UPD: as pointed out here, the official solution of 2053I2 - Affectionate Arrays (Hard Version) is wrong. We are not sure that the problem is solvable with the current constraints. We will decide how to deal with this issue within tomorrow.

UPD: the problem I2 was removed from the official contest. Its statement has been corrected for future use. The affected participants have been unrated from the contest.

UPD: Congratulations to the winners!

  1. jiangly
  2. ecnerwala
  3. Benq
  4. Egor
  5. Radewoosh
  6. Petr
  7. Ormlis
  8. ksun48
  9. Nachia
  10. EnofTaiPeople

We are pleased to announce that NEAR has supported the round!

The featured prizes in NEAR are:

  • Ⓝ 512 for the first place,
  • Ⓝ 256 each for places 2 and 3,
  • Ⓝ 128 each for places 4 to 7,
  • ...
  • Ⓝ 1 each for places 512-1023 places.

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Announcement of Good Bye 2024: 2025 is NEAR
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By MikeMirzayanov, 2 weeks ago, In English

Hello, Codeforces!

I'm excited to invite you to participate in MaraTON Challenge 1, our first marathon in collaboration with the TON Foundation. It's great to see our partnership with TON thriving and moving forward.

Take part in the challenge →

The challenge is brought to you by TON blockchain engineers, some of whom are community members. Special thanks to SpyCheese for preparing the problem!

The competition will run for three weeks, starting on Dec/23/2024 16:35 (Moscow time). Get ready to dive deep into the technical details of the blockchain world — it's worth it.

Winners will receive amazing prizes:

  • 1st place: 8,000 USDT
  • 2nd place: 5,000 USDT
  • 3rd place: 3,000 USDT
  • 4th–10th places: 2,000 USDT each
  • 11th–20th places: 1,000 USDT each

Additionally, there will be bonus prizes for the leaders throughout the competition. Starting December 25th and continuing daily until January 13th at 13:35 (UTC), we will award bonus prizes to the top five leaders of the day:

  • 1st place: 250 USDT
  • 2nd place: 125 USDT
  • 3rd place: 75 USDT
  • 4th–5th places: 50 USDT each

Please note that these prizes will be distributed after full testing of all submissions made by 13:35 (UTC) on the respective day. The results are published here: https://mirror.codeforces.com/contest/2054/leadershipAwardsStandings

Join the competition — it's truly something new and exciting on Codeforces!

* All payments will be made to a TON wallet. All payouts (including those for daily leadership) will be issued after the final results are announced.
* In case of ties in the leaderboard, the participant who first achieved the score will rank higher for prize distribution.
* Please note that this is an individual competition. Collaboration, discussing ideas, or using shared code is prohibited. Please adhere to the rules regarding the use of third-party code.

UPD: Here is the link to the table with the current progress on rewards for daily leaders: https://mirror.codeforces.com/contest/2054/leadershipAwardsStandings

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By BledDest, 12 days ago, translation, In English

Neapolis University Pafos

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. Curious? Check out the CSAI curriculum now. Limited scholarships available — don't miss your chance to study in Europe for free!

On Dec/24/2024 17:35 (Moscow time) Educational Codeforces Round 173 (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 7 problems and 2 hours to solve them.

The problems were invented and prepared by Artem Ferume Ilikaev, Ruslan AcidWrongGod Kapralov and me. We would like to thank Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces. Also, big thanks to problem testers: Um_nik, alex.dobleaga, Stanislau, Karabutsa, Golovanov399, Timur2006, shnirelman, adedalic.

Attention: the contest uses some problems from the onsite stage of the KFU Olympiad, so if you participated in it, please refrain from taking part in the round.

Good luck to all the participants!

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By BledDest, history, 2 weeks ago, In English

Hello, Codeforces!

On Dec/22/2024 17:35 (Moscow time) the Codeforces Round 995 (Div. 3) will start. The round will contain 7 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. Participants with rating below 1600 can also use unrated registration to participate 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 7 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 Neon, fcspartakm, awoo, adedalic and me. We hope you enjoy solving them!

We would also like to thank MikeMirzayanov for his Codeforces and Polygon platforms, and Vladosiya for coordinating the round.

The contest was tested by shnirelman, k1sara, leovl48, jai_hanuman_orz, saba_goduadze, SashaT9, RohitLakra and rahmanmehraj627. Thank you for helping us in evaluating the difficulty better and in getting rid of ambiguity in statements!

Good luck, and see you during the contest!

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By MikeMirzayanov, 2 weeks ago, In English

Goodbye, 2024. Hello, 2025!

Dear Santa Claus,
Please make 2025 a happy year—not just for me, but for everyone. We all need this.

Hello, 2025!

And of course, we have our traditional gifts!

Change Handle Feature

Hurry! Until the 10th of January, you can change your handle (but only once)! Note that you can roll back the changes or request another handle change only after a year. Choose wisely!

You can change your handle to a new one that hasn’t been used by anyone else, or to one that you’ve previously used. Links to your old profile will automatically redirect to your updated profile.

Again this year, if you’ve participated in at least 10 rounds, you can request the handle of an inactive participant. This means the participant must have had a period of activity on Codeforces lasting at most 180 days, and this activity must have occurred in 2020 or earlier. The inactive participant must not have posted comments, messages, or similar content, and they must not have participated in more than 2 contests. In such cases, the handle will be automatically renamed, and the original owner will be notified via email. If the original user requests their handle back, we will roll back the change and restore your previous handle.

If you’re unable to change your handle, it means some of the requirements have not been met. Please do not ask me to intervene manually. I especially dislike requests such as, "This is my second account; I took an interesting handle myself." I'm not Santa Claus!

Speaking of handles, I always reminisce about one particular story. Once, a user sent me this 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 your profile settings. Happy New Year!

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By Evirir, 3 weeks ago, In English
A drawing of Evirir the dragon
Art by Evirir

Hello / Selamat sejahtera / 你好 Codeforces! ^.=.^

We, CSQ31, Evirir, and YouKn0wWho, are excited to invite you to Codeforces Round 994 (Div. 2) on 20.12.2024 17:35 (Московское время)!

In this round, you will learn more about Evirir the dragon and help (or stop) them as they wreak havoc and escape from a wizard.

You will solve 6 problems in 2 hours.

The score distribution is 5007501000175022502750.

There will be at least one interactive problem, so please read the guide for interactive problems if you are unfamiliar with them.

We would like to thank everyone who made this round possible:

Fun fact: As far as we know, this is the first round by Malaysians since 2020 (last being Codeforces Global Round 10)!

UPD: The score distribution has been added.

UPD 2: Editorial

UPD 3: Congratulations to the Top 5!

Div. 2:

  1. rainboy
  2. natural_fruits
  3. Aestivate
  4. trunkty
  5. 1.618034

Div. 1 + 2:

  1. Rubikun
  2. arvindf232
  3. antontrygubO_o
  4. StarSilk
  5. Otomachi_Una

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By Little09, 3 weeks ago, In English

Hello, Codeforces!

We are pleased to announce the resumption of the Global Rounds. Thanks to XTX Markets for supporting the initiative! In 2024, we will hold 4 such rounds. The series results will take into account the best 3 participations out of 4.

On Dec/19/2024 17:35 (Moscow time) we will host Codeforces Global Round 28.

Codeforces Global Round 28 marks the fourth round in the 2024 series of Codeforces Global Rounds. These rounds are open and rated for everyone.

The prizes for this round are as follows:

  • The top 30 participants will receive a t-shirt.
  • 20 t-shirts will be randomly distributed among participants ranked between 31 and 500, inclusive.

The prizes for the 4-round series in 2024:

  • In each round, the top-100 participants get points according to the table.
  • A participant's final score will be the sum of the points they earned in their 3 highest-placing rounds.
  • The top 20 participants across the series will receive sweatshirts and placement certificates.

We extend our gratitude to XTX Markets for supporting the global rounds initiative in 2024!

The 9 problems were authored by our 4 authors: JoesSR, cmk666, wsyear and Little09.

We would also like to thank:

Round Information:

  • Duration: 180 minutes.
  • Number of problems: 9 problems with 1 subtask.
  • Score distribution: 250500100012501750200022502750(3000+3000).

We eagerly anticipate your participation!

UPD:

Congrats to the winners!

  1. jiangly
  2. turmax
  3. dorijanlendvaj
  4. ksun48
  5. hos.lyric
  6. Nachia
  7. jiangbowen_
  8. Ormlis
  9. maroonrk
  10. dXqwq

First Solves:

A: dXqwq
B: dXqwq
C: Marcin_smu
D: jiangly
E: sevlll777
F: dXqwq
G: BlackLily
H: jiangly
I1: jiangly
I2: nobody solved

UPD2: Editorial.

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Announcement of Codeforces Global Round 28
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