Привет! В 01.08.2022 17:35 (Московское время) начнётся Codeforces Round 811 (Div. 3) — очередной Codeforces раунд для третьего дивизиона. В этом раунде будет 6-8 задач, которые подобраны по сложности так, чтобы составить интересное соревнование для участников с рейтингами до 1600. Однако все желающие, чей рейтинг 1600 и выше могут зарегистрироваться на раунд вне конкурса.

Раунд пройдет по правилам образовательных раундов. Таким образом, во время раунда задачи будут тестироваться на предварительных тестах, а после раунда будет 12-ти часовая фаза открытых взломов. Мы постарались сделать приличные тесты — так же как и вы, мы будем расстроены, если у многих будут падать решения после окончания контеста.

Вам будет предложено 6-8 задач и 2 часа 15 минут на их решение.

Штраф за неверную попытку в этом раунде (и последующих Div. 3 раундах) будет равняться 10 минутам.

Напоминаем, что в таблицу официальных результатов попадут только достоверные участники третьего дивизиона. Как написано по ссылке — это вынужденная мера для борьбы с неспортивным поведением. Для квалификации в качестве достоверного участника третьего дивизиона надо:

• принять участие не менее чем в пяти рейтинговых раундах (и решить в каждом из них хотя бы одну задачу),
• не иметь в рейтинге точку 1900 или выше.

Независимо от того являетесь вы достоверными участниками третьего дивизиона или нет, если ваш рейтинг менее 1600, то раунд для вас будет рейтинговым.

Спасибо MikeMirzayanov за платформы, помощь с идеями для задач и координацией нашей работы. Задачи были придуманы и написаны командой Университета ИТМО: MikeMirzayanov, myav, Gol_D, Aris, senjougaharin, мной Vladosiya.

Также большое спасибо yorky, Jostic11, turmax, oversolver, ivanz, antonis.white, molney, KerakTelor, andrey.starodubtsev, Ahmad45123, myway, sofiaasta, Muhammad98 за тестирование раунда и весьма полезные замечания.

Всем удачи!

UPD: Разбор

Hello, Codeforces!

A wonderful summer holiday! After College Entrance Examination, we are extremely delighted to invite you to our second round, CodeTON Round 2 (Div. 1 + Div. 2, Rated, Prizes!), which will be held on Jul/31/2022 17:05 (Moscow time). Note the unusual start time of the round.You are given 8 problems and 2.5 hours to solve them.

All problems were written and prepared by Cirno_9baka, CoupDeGrace, Sugar_fan, ODT, Yakumo_Ran, farmerj, MagicalFlower, izlyforever, kuangbin, mejiamejia, ugly2333 and me.

Task statements and editorials will also be available in Chinese (Simplified) and Chinese (Traditional) after the contest.

We are sincerely thankful for the help provided by:

• 3.141592653, emorgan, errorgorn, SevenDawns, prabowo, why_no_girlfriend, valeriu, arvindr9, ExplodingFreeze, Huah, chenkuowen, plagues, antontrygubO_o, lych123, YunQian, magnus.hegdahl, Bench0310, Roundgod, njupt_lyy, null_awe, aniervs, Savior-of-Cross, dorijanlendvaj, Suiseiseki, dannyboy20031204, Lucina, ChthollyNotaSeniorious, JianfengZhu, aaaaawa, leukocyte, RiverHamster, -skyline-, Nanako, Nezzar, I.Gleb, glebustim, Y25t, gisp_zjz, Mitsukasa_Ayase, ustze, Vladithur, IIIIndex, Acfboy, 127.0.0.1, tibinyte, i_wyxkk_ak, TML104, spookywooky, 4qqqq, CSP_Sept, marzipan, efimovpaul, Erkhemkhuu, ak2006, NeuraXmy, RomkaRS, bpaT_Kapaca, sus, snowysecret, 755352046, IgorI, and Kieray for testing and good advice

• 74TrAkToR for his excellent round coordination and help with preparation

• MikeMirzayanov for great systems Codeforces and Polygon

• MinakoKojima, Ynoi, Suiseiseki for proposing problems that didn't been used in the final version of the round.

• Nanako, absi2011, Nezzar, QAQAutoMaton, rgnerdplayer for helping prepare the problems.

• magnus.hegdahl for strengthening the data of one problem (but because the problem was too hard, we removed it)

• emorgan for reviewing the statements

• dannyboy20031204 for traditional chinese statement and editorial

• You, for participating!

This is our second round! Great efforts have been put in during the past year. We are sincerely looking forward to your participation and we hope everyone will enjoy it. Besides, this round is sponsored, which indicates that everyone has an opportunity to get the prize!

Good luck!

UPD1: Here is the score distribution:

500-750-1250-1750-2000-2750-3500-(2250+2750)

UPD2:Tutorial is available.

UPD3: Simplified Chinese tutorial is available.

UPD4: Traditional Chinese tutorial is available.

UPD5: Congratulations to the winners

1. tourist
2. jiangly
3. ksun48
4. Rewinding
5. djq_cpp
6. maroonrk
7. cnnfls_csy
8. he_____hezhou
9. 353cerega
10. WYZFL
11. ecnerwala

UPD6: Simplified Chinese statement is available.(please download it and open it with edge)

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 2.

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

Since July, 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 2 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 2 and hope you enjoy the contest!

Hello, Codeforces.

I have wanted for a long time and now, finally, I sat down and did it.

Many of you are familiar with my Testlib project. This is a library that helps you develop problems if you are using C++. In the case of problems for Codeforces rounds, its use is mandatory. It seems to me that it is almost a de facto standard for preparing materials for completely different olympiads and competitions.

The history of С++-Testlib is almost lost in centuries, I published the first version in 2005.

Nowadays, making edits to Testlib has become tricky. The code grown to thousands of lines, also it has too long a history. This increases the likelihood of accidentally changing some aspect of behavior, which will jeopardize the holding of a Codeforces round or another important competition. In short, making a bug in this code or changing behavior anywhere is highly discouraged.

So I recently took the plunge and wrote some tests for Testlib. Here's what tests can do now:

• check that all cpp files in the repository are compiled (test test-000_compile-all-cpp)
• check the plausibility of the behavior of a simple sval.cpp validator on a series of files (test-001_run-sval test)
• check the plausibility of the behavior of the two checkers fcmp.cpp and wcmp.cpp on a series of files (test test-002_run-fcmp-wcmp)
• check that the behavior of the random number generator has not changed (test test-003_run-rnd)
• check the behavior of some functions and the behavior of InStream and opt in a series of unit tests (test test-004_use-test.h)

More good news. All this was automated through GitHub Actions. Tests are automatically run on any push or pull request.

I am the coordinator of Round #810. I will be brief and clear.

The div1E problem was copied by one of the two authors, it was not a coincidence.

For this reason, the div1 part of the round is unrated. Div2 stays rated.

Sometimes known problems appear in a contest, it happened to me as an author and to any problem setter who has organized many contests. This is never a reason to make a round unrated. Today something different happened, the problem was deliberately copied and the author did not tell anything to anybody (not even to the other author). Codeforces (and me personally) condemns this behavior.

A final personal remark: I feel sad. Please future authors: do not copy problems. It's a waste of everyone's time.

Hello Codeforces!

We are glad to invite you to our Codeforces Round Codeforces Round 810 (Div. 1) and Codeforces Round 810 (Div. 2) which will be held on 24.07.2022 17:35 (Московское время). This round will be rated for participants of both divisions. Participants in each division will be offered 5 problems and 2 hours to solve them. The two divisions will share 3 problems.

The problems are prepared by me and zxyoi. We hope that everyone will enjoy this round!

We are sincerely thankful for the help provided by:

• dario2994 for his marvelous coordination of this round,

• wyyxhjth for providing feedback on our early ideas,

• flukehn,FairyWinx,Pinkyhead,Vladithur,naman1601,dorijanlendvaj,c337134154,STommydx,LeoRiether,hxu10,Warriors_fsy,idxcalcal,jiaangk_,yakamoto,kiwiHM,Joyemang,forxen for testing our round and giving detailed feedback,

• FairyWinx for finding that one of our problems is coincident with a well-known problem (We replaced it),

• Vladithur for polishing our statements,

• KAN for his great help to our round,

• MikeMirzayanov for the amazing Codeforces and Polygon platforms!

We tried our best to have detailed, clear, and short statements. I think that anyone can find some interesting problems in this contest. We suggest to read all the statements.

The score distribution will be announced later.

Wish you good luck and high rating!

UPD

For some reason, we have removed one of our problems. So now participants in each division will be offered 5 problems and 2 hours to solve them.

The score distribution is:

Div2: $$$500-1000-1500-2000-3000$$$

Div1: $$$500-1000-1750-2000-2750$$$

We have some more testers now, let's thank them!

UPD2

We adjusted our score distribution slightly.

UPD3: the Div. 1 part of the round is declared unrated.

UPD4

Sorry for the late editorial.

UPD5

Congratulate to winners:

Div1

1. nantf

2. ko_osaga

3. Rebelz

4. The_Noble_Brahman_Bison

5. VivaciousAubergine

Div2

1. csyakuoi

2. Linkus

3. yaoxi

4. RGB_ICPC1

5. bajablast

Hi. I'm organizing an online IOI-preparation camp in collaboration with Huawei. Every day will be a 5-hour virtual contest, then my problem analysis, and sometimes a lecture. There will be at least 4 contests and 2 lectures.

We will do some old IOI contests (2013?) from the IOI archive, CEOI (2015-2016?), or maybe JOI/JOISC — to be decided this weekend. I don't want to do recent years like 2021 because most participants already covered it. The example lecture topics are those from Range Queries or Trees in Usaco Guide Platinum.

The camp is free for IOI 2022 participants. For everybody else, the video recordings will be posted on Youtube after the camp. By participating you get the live experience (Discord, asking questions, competing with others, leaderboards).

Dates: 25.07-2.08 (updated)
Time of every analysis/lecture: 14:00 UTC / 16:00 CEST
Price: free for IOI participants, 40 USD for everybody else
Platform: Discord & Codeforces & uj.oz (?)

Big thanks to Huawei UK R&D for sponsoring this camp.

EDIT: I'm now aware of CEOI collision. There's nothing I can do about it :(

Schedule:
25.07 — CEOI 2016 day 1
26.07 — CEOI 2022 day 1 + lecture
27.07 — CEOI 2016 day 2
28.07 — CEOI 2022 day 2
29.07 — lecture + homework
weekend off
1.08 — CEOI 2017 day 1
2.08 — CEOI 2017 day 2

Participants voted to cover CEOI instead of IOI to avoid problems that they already know.

Привет, Codeforces!

В Jul/21/2022 17:35 (Moscow time) состоится Educational Codeforces Round 132 (Rated for Div. 2).

Продолжается серия образовательных раундов в рамках инициативы Harbour.Space University! Подробности о сотрудничестве Harbour.Space University и Codeforces можно прочитать в посте.

Этот раунд будет рейтинговым для участников с рейтингом менее 2100. Соревнование будет проводиться по немного расширенным правилам ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением, равен 10 минутам. После окончания раунда будет период времени длительностью в 12 часов, в течение которого вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования.

Вам будет предложено 6 или 7 задач на 2 часа. Мы надеемся, что вам они покажутся интересными.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Владимир vovuh Петров, Иван BledDest Андросов и Максим Neon Мещеряков. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Удачи в раунде! Успешных решений!

Также от наших друзей и партнёров из Harbour.Space есть сообщение для вас:

ВОЗМОЖНОСТь ДЛЯ РАБОТЫ И УЧЕБЫ В БАНГКОКЕ — B.GRIMM POWER x HARBOUR.SPACE UNIVERSITY

Компания B.GRIMM POWER в сотрудничестве с Harbour.Space University предлагает стипендии для получения степени бакалавра и магистра в области Data Science и опыт работы в одной из ведущих компаний-разработчиков инфраструктуры в Таиланде.

B.Grimm Power PCL (B.Grimm Power) — компания из Таиланда по производству и распределению электроэнергии. B.Grimm Power занимается разработкой, финансированием, строительством и эксплуатацией электростанций. Ассортимент продукции включает в себя солнечную, гидроэнергию, энергию ветра и дизельное топливо.

Мы ищем кандидатов от младшего до среднего звена для работы над решением задач в различных областях, таких как:

• Анализ данных
• Системная интеграция
• ИИ
• Моделирование прогнозирования

Все успешные кандидаты будут иметь право на получение стипендии со стопроцентной оплатой обучения (22.900 евро в год), предоставленную B.GRIMM POWER.

Обязательства:

Обучение: 3 часа в день ‍

За год обучения вы завершите 15 модулей (длительность каждого 3 недели). Ежедневная учебная нагрузка составляет 3 часа, плюс домашнее задание, которое нужно выполнить в свободное время.

Работа: 4+ часа в день ‍

Погрузитесь в профессиональный мир во время обучения. Вы будете учиться у лучших и с первого дня сможете применять свои новые знания на практике.

Требования:

• Опыт работы в отрасли
• Тяга к обучению
• Предпринимательский менталитет
• (Знание тайского языка приветствуется, но не обязательно)

UPD: Разбор опубликован

Hi Codeforces,

We're excited to invite you to Codeforces Round 809 (Div. 2), which will take place at Jul/18/2022 17:35 (Moscow time). All problems were created and prepared by lunchbox, lce4113, and me. It will be rated for all participants with ratings lower than 2100.

Thanks to the people that made this round possible:

• IgorI for coordinating the round, patiently guiding us through the preparation process, and translating all statements to Russian.
• KAN, for guiding and assisting IgorI in the coordination.
• Apple_Method, izhang, lethan3, moo., null_awe, and ezraft for proposing problems that didn't make it to the final version of the round.
• PurpleCrayon for feedback and suggestions in the early stages of the round.
• Our testers, for their time and feedback: EnDeRBeaT, Queue, AlperenT, FairyWinx, ak2006, TheScrasse, sus, SirPh, litesam, asrinivasan007, Igorbunov, Runtime-Terr0r, timreizin, and Aaeria.
• MikeMirzayanov for the excellent platforms Codeforces and Polygon.

You will be given 2 hours to solve 5 problems, one of which will be divided into 2 subtasks. The scoring distribution will be announced later.

UPD: The scoring distribution will be $$$500 - 1000 - 1250 - (1000 + 1250) - 2250$$$.

UPD2: The editorial has been posted at https://codeforces.net/blog/entry/105008.

UPD3: Winners

Official

1. WYZFL
2. c8k
3. tiger1926
4. b6e0
5. iztrax

Everyone

1. tourist
2. SSRS_
3. WYZFL
4. Rubikun
5. noimi

Hello, Codeforces!

Imakf and I are glad to invite you to Codeforces Round #808 (Div. 1) and Codeforces Round #808 (Div. 2), which will take place on Jul/16/2022 17:35 (Moscow time). In both divisions, you will be given 6 problems and 2 hours to solve them all.

We would like to thank:

• Monogon for his 1-year cute coordination and very helpful discussion.
• KAN for the great help with round preparation.
• Wolam for his discussing the problems with us, which helps us to find the solution.
• smg23333 for donating his csgo time to test the problems in advance.
• AliShahali1382, SecondThread, wxhtzdy, taran_1407, Retired_cherry, antontrygubO_o, Tlatoani, errorgorn, hg333, kassutta, timreizin, Taday, Qiulyqwq, dorijanlendvaj, arvindr9, gamegame, EmptySoulist, prabowo, Yakumo_Ran, star_xingchen_c, generic_placeholder_name, 74TrAkToR and Ari for testing the round and their invaluable feedbacks.
• MikeMirzayanov for amazing platform Codeforces and Polygon.
• geranazavr555, KAN, myav and unreal.eugene for translating the statements into Russian.

Score distribution will be announced before the round.

Wish you all wouldn't gain negative ratings in this round! (This is theoretically possible XD)

UPD1: Score distribution is

Div 2: $$$500 - 1000 - 1500 - 1750 - 2250 - 3000$$$

Div 1: $$$500 - 750 - 1250 - 1750 - 2500 - 3250$$$

UPD2: Editorial

UPD3: Congratulations to the winners!

Div 1

1. Isonan
2. djq_cpp
3. tourist
4. jiangly
5. Um_nik

Div. 2

1. _WidowMaker_
2. N193r
3. Ayaka_s_Dog
4. PaiGuChicken
5. NothingOccurred

Hello Codeforces,

We are glad to invite you to Codeforces Round 807 (Div. 2), which will be held on 15.07.2022 16:35 (Московское время). As usual, the round will be rated for participants with ratings lower than 2100, while those who have higher ratings are encouraged to participate unofficially. Please note the unusual start time.

You will be given 6 problems to be solved in 2 hours and 15 minutes. There may or may not be interactive problems, so you are encouraged to prepare in case they do appear by reading this guide.

The round is authored by abc241 and me, while joining us is also inwbearX who contributed significantly to the preparation. This is our first time setting rounds in Codeforces, and it wouldn't be possible if there were no support from the following people.

• errorgorn for fantastic coordination.
• KAN, mtw, geranazavr555, unreal.eugene and MikeMirzayanov for translating the statements into Russian.
• antontrygubO_o, kevinxiehk, mango_lassi, Adam_GS, mtw, Utkarsh.25dec, yz_, thanhchauns2, TLP.39, 36champ, jampm, DeMen100ns, Neothehero, and somerandomaltacc3034 for testing the round.
• MikeMirzayanov for Polygon and Codeforces.

The score distribution is $$$500$$$ — $$$1000$$$ — $$$1250$$$ — $$$1750$$$ — $$$2500$$$ — $$$3000$$$.

We are looking forward to your participation. Good luck and enjoy our round!

Update: the editorial is up!

Update 2: Winners!

Div. 2

1. stemroot
2. UtopianZ
3. WYZFL
4. H_stove
5. myeeye

Div. 1 + Div. 2

1. tourist
2. SSRS_
3. stemroot
4. Um_nik
5. arvindf232