Hi again, Codeforces!

fishy15, flamestorm, ScarletS, saarang and I are glad to invite you to our second Constructiveforces round, Codeforces Round 836 (Div. 2), which will be held on Nov/25/2022 18:35 (Moscow time). The round will be rated for participants with rating lower than 2100.

Please note the unusual time!

We'd especially like to thank:

• errorgorn and KAN, for their fantastic coordination and translation of the round!

• MikeMirzayanov, for creating the amazing Codeforces and Polygon platforms!

• Our testers dorijanlendvaj, PurpleCrayon, Ari, atodo, maomao90, prvocislo, nor, AlperenT, phattd, KrowSavcik, idk321, SlavicG, tenth, Nahian9696, Beacon, nyaruhodo, _Vanilla_, MEX1, Awesome3.14, JuanPabloAmezcua, anishde85, coder_sounak, jampm, Codula, ak2006, IAmTheHazard, and bakekaga for testing the round, catching any mistakes and providing lots of valuable feedback! We tried to get a large range of testers with different coding experiences so that everybody enjoys the round.

• And you, the contestant, for taking part in and hopefully enjoying our contest!

You will have 2 hours to work on (and solve!) 6 problems. At most one of the problems will be interactive. Make sure to read this blog and familiarize yourself with these types of problems before the round! You are highly encouraged to read all the problems ;).

The scoring distribution is $$$500-1000-1500-1750-2250-3000$$$.

Good luck, and see you on the scoreboard!

UPD1: Thanks to ak2006 for making video editorials for some of the problems.

UPD2: Editorial is out!

UPD3: Congrats to the winners:

Div. 1 + 2:

1. jiangly
2. SSRS_
3. kotatsugame [tie]
4. Maksim1744 [tie]
5. March_7th

Div. 2:

1. March_7th
2. is_this_Furry
3. puffins
4. DongXuelian
5. ouqI

Hello Codeforces!

mesanu, flamestorm, MikeMirzayanov and I are glad to invite you to Codeforces Round 835 (Div. 4)! It starts on Nov/21/2022 17:35 (Moscow time).

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.

We would like to thank:

• RedstoneGamer22, tibinyte, haochenkang, badlad, qwexd, nyaruhodo, Phantom_Performer, tolbi, AlperenT, Bakry, prvocislo, Gheal, keta_tsimakuridze, KrowSavcik, BucketPotato, pashka, MikeMirzayanov for testing the round!

• Max_Calincu, TimDee, MikeMirzayanov for helping with Russian translations!

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

Good luck!

UPD: Editorial is posted.

Hello, Codeforces!

Members of team EZEC are glad to invite you to participate in Pinely Round 1 (Div. 1 + Div. 2), which will start on Nov/20/2022 17:35 (Moscow time). You will be given 7 problems, one of which has a subtask, and 2 hours and 30 minutes to solve them. The round will be rated for everyone. It is greatly recommended to read all the problems.

There is at least one interactive problem, so please see the guide of interactive problems if you are unfamiliar with it.

We would also like to thank:

• Our red sun orzdevinwang, the youngest TOP10 coder in history, for illuminating our path.
• Our great emperor antontrygubO_o for cooperating and coordinating with us to make this round happen. He saved the round by contributing his problem when a problem was found similar to an existing problem.
• Our authors for providing great ideas (both rejected and accepted): orzdevinwang, dXqwq , Forever_Pursuit, SpaceJellyfish, unputdownable, RedreamMer, pigstd. Without them, the round couldn't have been prepared so quickly.
• Our testers for high-quality testing and valuable advices: Ecrade_, cmll02, Redcrown, mtw, jqdai0815, pocafup, ieeqwq, Mooos, Justcyl, do_while_true, Ari, ffao, InternetPerson10, feecIe6418, __ZMF__, dingdingsb, PubabaOnO, lqx2005, myee, louhao088088, LinkZelda, Inversentropir-36, KagamineRin, zaozao_zmx1, Promisenxt, Tom66, RedLycoris, DearMargaret, Lynkcat, zeliboba, Kostroma, iwalainz, zemen, MELNIKOFF_OLEG, AndreySergunin, _overrated_, nick.sh, oleg_smirnov2001, kokokostya, lxyb, halin.george, Endagorion, I_love_myself, SSerxhs, LMOliver, George1123, Um_nik, 244mhq, apeiya.
• MikeMirzayanov for the great systems Codeforces and Polygon.

Fun facts:

• Anton reviewed 18 problems in total.
• This is the 13th round of EZEC. Here are some previous rounds: Round 11 on Luogu, Round 12 on nowcoder.
• The team has an anime character EZEC-chan (the girl in the image), hope you like it :3
• orzdevinwang found a better solution of F the day before the contest.

This round is made possible with the support of Pinely!

Pinely is a privately owned & funded algorithmic trading firm, our main focus is set on high frequency and ultra low latency trading.

We are a team of mathematicians, programmers, engineers and computer scientists driven by the immense passion for knowledge. We constantly face various challenges such as developing strategies for trading, optimizing trading systems to achieve the lowest latency reactions to various market events, saving and processing large volumes of historical data. The work we do requires a high ability to create effective C++ code, algorithmic thinking and mathematical intuition, which attracts winners, awardees and medalists of various competitions in the respective fields such as ICPC, IMC, HITB PRO CTF and Google HashCode etc.

Find out more about us on our website pinely.com or from our employees registered here on CF.

If you want to join our team please send your CV to [email protected] or fill in the form

Top 30 contestants and 10 random contestants placed 31-100 will receive a branded Pinely hoodie :)

The statements were made as briefly and clearly as we could. GLHF!

Scoring distribution: 500 — 1000 — 1250 — 1750 — 1750 — (2500+2000) — 3500

UPD1: Editorial is out. link.

UPD2: Congratulations to the winners:

• tourist
• dorijanlendvaj
• mnbvmar
• fivedemands
• Benq
• jiangly
• maroonrk
• inaFSTream
• hitonanode
• gisp_zjz

Pinely is a privately owned & funded algorithmic trading firm that is growing by leaps and bounds. We are based in Singapore, the Netherlands and Cyprus and our main focus is set on high frequency and ultra low latency trading.

We work in synergy to create a leading-edge & robust technology with the sole aim of exceling and establishing ourselves amongst the top trading companies around the globe. Our core team constantly faces various challenges such as developing strategies for trading, optimizing trading systems to achieve the lowest latency reactions to various market events, saving and processing large volumes of historical data.

We are a team of mathematicians, programmers, engineers and computer scientists, driven by an immense passion for knowledge. The work we do requires a high ability to create effective C++ code, algorithmic thinking and mathematical intuition, which attracts winners, awardees and medalists of various competitions in their respective fields such as ICPC, IMC, HITB PRO CTF and Google HashCode etc.

At Pinely we have a flat organizational structure with a collegial environment and an idea-driven culture to stay ahead of the curve.

Find out more about us on our website pinely.com or from our employees registered here on CF.

If you want to join our team please send your CV on [email protected]

This season we are happy to hold Pinely rounds on Codeforces. The first one will take place this sunday, on Nov/20/2022 17:35 (Moscow time). The round will be rated for all contestants.

Привет! В 18.11.2022 17:35 (Московское время) начнётся Codeforces Round 834 (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 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, Gornak40, senjougaharin и Vladosiya.

Также большое спасибо: mumumucoder, Enkognit, orloffm, TeaTime, ilyamzy, Olympia, moonveil, 74TrAkToR, molney, elseecay, bigDuck, Nickir, Be_dos, OAleksa за тестирование раунда и весьма полезные замечания. Список тестеров будет пополняться.

Всем удачи!

UPD: Разбор

Hello, Codeforces! (or as we say in romanian, "Nu renunţ la tine niciodată")

I am glad to invite everyone to participate in Codeforces Round 833 (Div. 2), which will be held on 12.11.2022 17:35 (Московское время).

This round will be rated for all participants with rating lower than 2100.

You will be given 6 problems and 2 hours to solve them. All of the problems are authored by me.

I would like to thank the following people, without whom this round would not have been possible:

• IgorI for his awesome coordination of the round and for helping me with problem preparation.
• feecle6418, SSerxhs, Gary2005, RUSH_D_CAT, atodo, BucketPotato, andrei_boaca, hochesh, JohnVictor, valeriu, powergee101, mejiamejia, jampm, alin_gb18, sutekine, tibinyte and ansergeyg for testing the round and providing valuable feedback.
• MikeMirzayanov for the great systems Codeforces and Polygon.

Here is the scoring distribution: $$$500−1000−1500−2000−2250-2750$$$

Good luck & have fun!

Edit 1: The round is over, the editorial can be found here.

Edit 2: Congratulations to the winners:

Div 1 + Div 2:

• Um_nik
• Geothermal
• maximumSHOT
• tute7627
• kektus

Div 2:

• KHIN_236807
• XenonKnight
• March_7th
• wiIIiam555
• Jarif_Rahman

Всем привет!

Уже сегодня, 12 ноября 2022 года в 15:00 (по Московскому времени) состоится третья командная интернет-олимпиада сезона 2022-23. Приглашаем вас принять в ней участие! Условия, как и обещалось, будут на Хэллоуинскую тематику.

Олимпиада пройдет в двух номинациях: в базовой и усложненной. Регистрация для двух номинаций общая, не забудьте зарегистрироваться на цикл командных интернет-олимпиад в этом сезоне перед началом олимпиады. Обратите внимание, что для участия в командных олимпиадах нужно зарегистрировать именно команду. Команда может содержать от 1 до 3 человек.

Ссылка на регистрацию команд доступна из данного анонса, а также на основном сайте интернет-олимпиад. Всю дополнительную информацию, а также расписание всех предстоящих командных интернет-олимпиад можно посмотреть на той же страничке.

Продолжительность олимпиады – 5 часов для усложненной номинации и 3 часа для базовой. В базовой номинации вам будет предложено 8 задач вместо 10, некоторые задачи будут на более простые темы и алгоритмы, в некоторых по сравнению с усложненной будут более мягкие ограничения.

Условия появятся на сайте и во вкладке "Файлы" тестирующей системы в момент начала олимпиады. Тестирующая система находится по адресу pcms.itmo.ru. Выбрать базовую или усложненную номинацию можно будет в тестирующей системе на вкладке "Соревнования" перед началом олимпиады. Мы рекомендуем не выбирать базовую номинацию, если у вас уже есть значительный опыт олимпиадного программирования, но конечный выбор остается за вами. Для выбора номинации надо будет либо приписать букву b или a к своему логину, либо просто выбрать номинацию в системе – пожалуйста, прочитайте актуальную информацию про это на главной странице перед началом олимпиады.

Олимпиаду для вас подготовили: Даниил Орешников (doreshnikov), Мария Жогова (Masha237), Владислав Власов (Vladosiya), Даниил Голов (DanGolov), Константин Бац (kbats183), Александр Гордеев (gordeve), Сергей Щербаков (Sergey140146659) и Тимур Гараев (the_timur).

Для связи с жюри можно использовать адрес электронной почты [email protected].

Удачи!

Hello, Codeforces!

The ICPC World Finals Dhaka will begin on November 10, 2022 at 11:00 (UTC+6). This is the culmination of the 2020-2021 ICPC season, and we have over 130 teams competing for the title of ICPC champion. Please join us on the live broadcast for the main event of the year in competitive programming; commentators will include ecnerwala, SecondThread, Egor, and more! There will also be a live mirror for you to solve the problems alongside the contestants!

Some useful links:

• ICPC Homepage
• World Finals Homepage
• World Finals Schedule
• Live Broadcast
• Live Scoreboard
• Contest Mirror/Judge!

All available broadcasts:

Good luck to all teams competing!

Hello, codeforces.

To unveil the full power of Kotlin and JetBrains tools, as well as their advantages in algorithmic problem-solving, we’ve invited two competitive programming stars to match their skills in solving Kotlin problems on stage at the ICPC World Finals.

Andrew ecnerwala He, one of the top competitive programmers in the world, will compete in a match against Kamil Errichto Debowski, Codeforces "Legendary Grandmaster" and Topcoder "Target." The match will be commentated by none other than Roman elizarov Elizarov, Kotlin Lead Language Designer.

You can join the stream on Kotlin by JetBrains youtube channel at Nov/07/2022 07:17 (Moscow time) and view submissions in the special Codeforces round Ecnerwala vs Errichto Kotlin Match. Only ecnerwala and Errichto can participate in the round, while you will be able to join as spectators.

We will reuse some problems from previous Div3 rounds. We mostly used round #748. And also, one problem was from round #627. A lot of thanks to MikeMirzayanov vovuh and MrPaul_TUser.

Good luck to both participants, and thanks to MikeMirzayanov for the great codeforces platform.

Hello, Codeforces! Or, as we like to say in Romania: Nu îmi amintesc să fi adresat întrebări, Codeforces!

I am glad to finally invite you to participate in CodeTON Round 3 (Div. 1 + Div. 2, Rated, Prizes!), which will start on Nov/06/2022 17:35 (Moscow time). You will be given 8 problems and 2 hours and 30 minutes to solve them. It is greatly recommended to read all the problems, statements are short and straight to the point.

I would like to thank:

• Artyom123 for prodigious coordination.

• AquaMoon, mejiamejia, ugly2333, Ecrade_ for huge help in preparation and authoring one of the tasks.

• errorgorn for being a VIP-tester.

• Lemur95, Gheal, Perpetually_Purple, Everule, IacobTudor, andrei_boaca, lucri, AlperenT, Kuroni, prabowo, lis05, Alon-Tanay, jeroenodb, Juve45, denis2111, Brodicico, Fanurie, huangzirui, satyam343, tfg, Sugar_fan, SlavicG, Vladithur,KrowSavcik, kevinxiehk, sharkycode,Alan, TimDee, Rhodoks, dannyboy20031204,TomiokapEace, Qingyu, lxlxl, ChthollyNotaSeniorious,PinkieRabbit, jerryliuhkg, valeriu, Chenyu_Qiu, jampm, izlyforever, njupt_lyy, RUSH_D_CAT,azureAmarantine, Erkhemkhuu, wh030115,ak2006, dorijanlendvaj, spookywooky, arvindf232, absi2011, AlexLorintz for testing the round and providing invaluable feedback.

• freak93 for morning refreshment.

• MikeMirzayanov for great platforms, codeforces and polygon!

Scoring Distribution: 500-750-1250-1750-2250-2500-3250-3500

The editorial has been published here!

And here are our winners!

• Benq
• zh0ukangyang
• WYZFL
• MagicalFlower
• feecIe6418
• QuietBeautifulThoughts
• p_b_p_b
• conqueror_of_tourist
• jiangly
• tourist

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 3.

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 3 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 3 and hope you enjoy the contest!