Привет, Codeforces!

В августе (с 1 по 10 число) мы проводим всероссийские летние студенческие сборы по программированию (школа "Саратов-2024"). Они пройдут в Энгельсе, в гостинице "Речная Долина" в 5 минутах от Волги. Сборы рассчитаны на 9 учебных дней и 1 выходной; в течение учебных дней будут как нетематические контесты (уровня сложности примерно как четвертьфиналы ICPC), так и лекции с тематическими контестами по ним.

Учебная программа в основном рассчитана на студентов с рейтингом примерно 1500-2200, но это, конечно, не обязательное условие для участия, а скорее ориентир в плане сложности лекций и контестов. Лекции будут читать:

• двукратный финалист ICPC, серебряный призёр NERC, автор Codeforces Educational Rounds, тренер команд Саратовского ГУ Михаил awoo Пикляев;

• двукратный финалист ICPC, координатор и автор Codeforces Educational Rounds, тренер команд Саратовского ГУ, председатель жюри Чемпионата Юга и Поволжья России Иван BledDest Андросов.

Предварительная программа лекций:

• sqrt-декомпозиция и другие sqrt-эвристики;

• префикс-функция, z-функция, алгоритм Кнута-Морриса-Пратта;

• бор, алгоритм Ахо-Корасик;

• суффиксный автомат и его применение.

Мы постараемся объяснить эти темы как можно более подробно, но на всякий случай напоминаю, что для понимания этого всего требуются базовые навыки работы с массивами и строками (знания string и vector из стандартных библиотек должно быть достаточно).

Стоимость участия в сборах ---- 33000 рублей с человека. В это входит и учебная программа, и проживание в гостинице, и трехразовое питание. Участвовать можно как в одиночку, так и в команде из двух-трех человек. С собой для участия нужно взять ноутбук с Wi-Fi адаптером для доступа к сети, в которой будут проводиться контесты.

Тем, кто заинтересован, нужно пройти предварительную регистрацию до 31 мая включительно (форма для регистрации доступна по ссылке. Пожалуйста, заполните все пункты формы, особенно информацию о хэндлах и достижениях участников (нам это нужно для того, чтобы определить, насколько простыми/сложными делать контесты).

Если интересует какая-то дополнительная информация о сборах, можете связаться с нами либо по телефону 88452213690, либо по e-mail: [email protected]

Надеюсь увидеть вас на нашей летней школе!

Ahoj, Codeforces!

We are excited to invite you to participate in Codeforces Round 945 (Div. 2), which will start on May/17/2024 17:35 (Moscow time).

The problems are authored by TimDee and prvocislo.

This round will be rated for participants whose rating is below $$$2100$$$. Participants with higher ratings are encouraged to participate out of the competition.

You will be given $$$6$$$ problems and $$$2$$$ hours to solve them. The scoring distribution is bellow. One of the problems will be interactive. Please read this blog to get familiar with this type of problems.

We would like to thank everyone, who made this round happen:

• You for participating in this round! I hope you will enjoy the problems!

• satyam343 for great coordination and discussion of the problem ideas!

• KAN for providing suggestions to help us make the round better

• MikeMirzayanov for the amazing Codeforces and Polygon platforms!

• Alexdat2000 for Russian translations

• Our loyal army of testers: A_G, Adam_GS, errorgorn, Dominater069, valeriu, atodo, Ritwin, MridulAhi, NemanjaSo2005, Sanat, tyr0Whiz yuvrajKharayat, 18o3, Phantom_Performer, mesanu, tushaar9876, madlogic, callmepandey, Scythe, htetgm, Blagoj, Non-origination, Abhishek_Srivastava and ✩₊ myvaluska ₊✧ , for pointing out mistakes and helping us improve the round!

• Last but not least, I, prvocislo, would like to thank atodo and misof for inspiring me to start with problem-setting.

Scoring distribution: $$$500-1000-1500-2000-2250-3000$$$

Good luck, have fun and see you on Friday! ✩₊˚

Upd: Congratulations to the Winners!

Div 2:

1) _MyGO_Tomori_

2) Sxy_Limit

3) LofiGirl

4) prins

5) SXWZ-Queenie

Div 1+2:

1) BucketPotato with first AK!

2) gamegame

3) hitonanode

4) abc864197532

5) peti1234

Upd2: Editorial is out!

Hi everyone!

We organized an onsite competitive programming contest at ETH Zürich on May 11th, 2024. The contest is now uploaded to the Codeforces gym at ETH Zurich Competitive Programming Contest Spring 2024.

The onsite contest was 5h long and we recommend for you to participate in teams. In the onsite contest only one computer was allowed but participants could access the internet freely. The difficulty of the problemset is slightly easier than a regional ICPC contest but also offers a few hard problems. Difficulty range is from div2 A to div2 G.

Thanks a lot to all problem setters: BenniKartefla, Lakii, Lebossle, MihneaDAVID, OhLee, TecTrixer, ackj, adamant, alagorithmet and mango_lassi.

Additionally, a big thanks to all our testers and reviewers: Petr, Evirir, CSQ31, atakanysr, FatihSolak, qwexd, AhmetKaan, Macdu, atli164, SATSKY_2024target_IGM, SuprDewd, Tagl, Tobo, wildfire032, fried-chicken, theodor.moroianu and sischu74.

Tutorial Slides can be found here.

Congratulations to the top 5 of the onsite contest:

1. mETHroners: GRT_2018, Meloric, paula
2. Mr Malnars Lethal Peppers: pavkal5, DBradac, dpaleka
3. uhh this should actually be first place, sorry, system error: AimShootReload, donentseto
4. ML and AC: miguell, Andrei1998
5. CrispyBeef: tiagodias, jonathanplsmith, Blackphoenyx

На официальном сайте Летней школы по компьютерным наукам открылся прием заявок. Школу для учеников 8-10 классов проводит факультет компьютерных наук НИУ ВШЭ совместно с Центром поддержки одарённых детей “Стратегия” в Липецке.

С 16 по 30 июля 2024 года Летняя школа по компьютерным наукам примет у себя талантливых школьников из 8-10 классов, желающих добиться высоких успехов в олимпиадах по информатике. Как и раньше, школу организует ФКН ВШЭ совместно с Центром поддержки одарённых детей “Стратегия” в Липецке.

Обучение в школе будет проходить в пяти параллелях: C, B', B, A' и A в соответствии с классом обучения в школе и уровнем подготовки участника. Основное внимание будет уделяться изучению алгоритмов, используемых при решении олимпиадных задач.

Отбор участников пройдет в несколько туров.

• Первый отборочный тур начнется 18 мая в 04:00 по московскому времени и продлится до 20 мая 23:59 по московскому времени.
• Второй отборочный тур начнется 8 июня в 04:00 по московскому времени и продлится до 9 июня 23:59 по московскому времени.

Отборочные туры проводится на платформе Codeforces. Каждый отборочный тур будет состоять из 30 задач, разделенных на 6 блоков по 5 задач: [C], [C-B'], [B'-B], [B-A'], [A'-A] и [A]. При отборе в каждую параллель будут учитываться только решенные задачи из блоков, соответствующих данной параллели. Например, если вы хотите попасть в параллель B', вам необходимо решать задачи из блоков [C-B'] и [B'-B].

Участие в школе платное и составляет в этом году 47 000 рублей. Участие для школьников из Липецкой области, а также для призеров и победителей заключительного этапа ВсОШ по информатике и математике бесплатно. Также через некоторое время на сайте школы будет опубликована информация о грантах на обучение от наших партнеров.

Желающим принять участие в ЛШКН-2024 нужно заполнить регистрационную анкету и решить вступительные задания той параллели, в которой они хотят учиться. Всем заполнившим анкету на указанный электронный адрес будет высылаться информация об отборе в школу.

Greetings Codeforces!

First things first, we would like to thank everyone who participated in the previous nine Kotlin Heroes competitions: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, Episode 8 and Episode 9.

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 improve 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 May 13, 2024, the real challenge begins! Kotlin Heroes: Episode 10 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!

Hi, Codeforces!

mesanu, SlavicG and I are very excited to invite you to Codeforces Round 944 (Div. 4)! It starts on May/10/2024 17:35 (Moscow time).

<begin-copy-pasted-part>

The format of the event will be identical to Div. 3 rounds:

• 5-8 tasks;
• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a trusted participant of the fourth 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 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

<end-copy-pasted-part>

Thanks a lot to the testers: Dominater069, nskybytskyi, ScarletS, Gheal, BucketPotato, JustJie, htetgm, Vladosiya!

We suggest reading all of the problems and hope you will find them interesting. Good luck!

UPD: Editorial is out!

Hello, Codeforces!

The ICPC Challenge World Finals in Luxor is approaching for some of you, and we are delighted to provide an additional exciting opportunity to compete open to all!

We are happy to invite you to the 2023 Post World Finals Online ICPC Challenge, powered by Huawei starting on May 6, 2024 at 15:00 UTC and ending on May 20, 2024 at 14:59 UTC.

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.

2023 Post World Finals Online ICPC Challenge powered by Huawei:

Start: May 6, 2024 15:00 UTC

Finish: May 20, 2024 14:59 UTC

We hope you'll enjoy this complex 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!

Back from the dead, we'd like to invite you to the online mirror of the Helvetic Coding Contest, Switzerland open championship! You can find past mirror from 2019, 2018, 2017, and 2016.

The Helvetic Coding Contest used to be held yearly at EPFL. This year, the Polympiads association is bringing it back alive! The contest itself took place on April the 13th, but the online mirror is scheduled on Saturday, 4th of May, 09:05 Swiss time. The duration is 4:30.

Rules:

• you can participate in teams or individually with a single computer (1-3 people),

• standard ACM-ICPC rules (no hacking),

• the contest is not rated,

• if you have participated in the onsite contest, please do not participate in the mirror.

Contrary to what the mirror's date might lead you to believe, this year's theme is Harry Potter. It features 7 series of 3 related tasks with increasing difficulty (easy/medium/hard). Note that we do not guarantee that all problems are solvable using python.

Thanks a lot to:

• Petr, Charbel, ScarletS, 3EVEHAR_KOAVA, AdrienVannson, bjornargh, and zehnsechs for setting and/or coordinating the problemsetting,

• matrix for preparing the technical setup of the contest

• paula, Macdu, McLovinn as well as problemsetters for testing the contest,

• All of Polympiads committee and on the day staff for making the contest possible,

• MikeMirzayanov for creating the amazing Codeforces and Polygon platforms!

UPDATE: Editorial is out, also available as a PDF. Thanks all for participating!

UPDATE 2: Congratulations to the winners who solved all 21 subtasks:

1. thinking: Ormlis, Mangooste
2. Captain take me!: crazy_sea, A_zjzj, 275307894a
3. japan406364961: Nyaan, kotatsugame, risujiroh
4. Qingyu Fan Club: xinyoudui, GapGapGap, InfiniteStarlight
5. Idea Generators Club: tedi_2.0, Denisov, Valera_Grinenko
6. 244mhq
7. jiangly

UPDATE 3: Also huge congratulations to the winners of the onsite round (no prewritten code or Internet access was allowed, so the conditions were a bit different):

1. Felt smart (might un-participate later) — 20 subtasks
2. Nameless Silly Moon — 18 subtasks
3. ***IsEvil? — 17 subtasks
4. Breakfast Master Toaster — 16 subtasks
5. Hairy Stofler — 16 subtasks
6. thethingswedoforpizza — 15 subtasks
7. huchibuchi — 15 subtasks

We hope you enjoyed the problems, please share your thoughts in comments!

Hello everyone,

FBI and SashaT9 are very exited to invite you to Codeforces Round 943 (Div. 3)! It starts on May/02/2024 17:45 (Moscow time).

The format of the event will be like any Div. 3 rounds:

• 6-8 tasks;
• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points);
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests.

Only trusted participants of the third division will be included in the official standings table. This is a forced 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 (or you are a newcomer/unrated), then the round will be rated for you.

We would like to thank:

• MikeMirzayanov for creating Codeforces and Polygon;
• Vladosiya for coordinating the round;
• feeder1, Umanity, Do_not_make_friends, Ryougi-Shiki, MAKMED1337, EyadBT, purinliang, waipoli, ksu_, _Dragon_, royhahayayaha, OAleksa, AlphaMale06, perekopska.d, Acanikolic73, Sheikh_Sady for testing the round and making it better.

Good luck and have fun!

UPD: Editorial.

久别无恙, Codeforces!

We are glad to invite you to take part in Codeforces Round 942 (Div. 1) and Codeforces Round 942 (Div. 2), which will start on Apr/30/2024 17:35 (Moscow time). You will be given 6 problems and 2 hours and 30 minutes to solve them in both divisions. Some problems will be divided into two subtasks.

The problems were authored and prepared by N_z__, wyrqwq, yinhy09 and me rui_er.

We would like to thank:

• TheScrasse for his perfect coordination.
• Alexdat2000 for Russian translation.
• negative1, tzl_Dedicatus545 and lelml for providing some rejected problem proposals and discussing problems with us.
• peti1234 and A_G for LGM testing.
• 10circle, le0n, Clein.qwq, AC-Automation, LMydd0225 and prvocislo for red testing.
• Survivor_winner, _rey, lvkaiyi0811, heaksicn, fishy15, FzArK, Error_Yuan, golions and jamesbamber for orange testing.
• zplqwq, StudyingFather, htetgm, carnation13, purp4ever and Tricopter for violet purple testing.
• tianbincheng, dxbt, LaMatematica14, OgradL, newb_programmer, joaozao, ssshanto, Quinx and 1egend for blue testing.
• lzqy__, stalkkk_19, madsere and Alenygam for cyan testing.
• Amirben for green testing.
• acoatoitgs for gray testing.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

• You

  for participating in this round.

Score distribution:

• Div. 2: 500 — 750 — 1500 — (1000 + 1500) — 2500 — 3500
• Div. 1: 750 — (500 + 750) — 1250 — 1750 — (1750 + 1000) — 3500

We hope you'll like the problemset!

UPD: Congrats to the winners!

Div. 2:

1. 3_m
2. RinaRin
3. eightniko
4. liumohan
5. golomb

Div. 1:

1. tourist
2. jiangly
3. jqdai0815
4. gamegame
5. Kevin114514

Editorial is out.