Hello!

Welcome to Codeforces Round 850 (Div. 1, based on VK Cup 2022 - Final Round) and Codeforces Round 850 (Div. 2, based on VK Cup 2022 - Final Round) that will start on Feb/05/2023 15:05 (Moscow time). Both rounds will be rated.

This round is a mirror of VK Cup 2022 Final — annual programming championship for Russian-speaking competitors organized by VK. VK Cup started in 2012 and has grown to be a five-track competition in competitive programming, Mobile, ML, Go, and JavaScript.

All the problems of Div. 1 round are authored and prepared by me, while KAN authored and prepared two problems for Div. 2. Thanks to errorgorn, irkstepanov, qwerty787788, Merkurev, IgorI, PavelKunyavskiy, izban, Alexdat2000, ashmelev, Akulyat, mike_live, Ekler, Kalashnikov for making this round better.

You will be given 6 problems and 3 hours to solve them.

UPD: Editorial

Congratulations to the winners:

1. ksun48
2. maroonrk
3. QuietBeautifulThoughts
4. Mr_Eight
5. ecnerwala

Hello Codeforces!

flamestorm, SlavicG, MikeMirzayanov and I want to invite you to Codeforces Round 849 (Div. 4).

It starts on 03.02.2023 17:35 (Московское время).

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 behaviour. 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.

Many thanks to the testers: _Vanilla_, badlad, Gheal, Phantom_Performer, Beacon, Nihad_Nabelsi, prvocislo, keta_tsimakuridze, Bakry, RedstoneGamer22, tibinyte, KrowSavcik, haochenkang, myvaluska, sandry24, BucketPotato, Vladosiya, pashka.

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

Good Luck!

UPD: Editorial is posted.

Hello, Codeforces!

adnan_toky and I are super thrilled to invite everyone to participate in Codeforces Round 848 (Div. 2), which will be held on 01.02.2023 17:35 (Московское время).

This round is rated for the participants with ratings strictly lower than 2100. You will be given 6 problems and 2 hours to solve them. All the problems are authored and prepared by adnan_toky and me. To get the 6 problems approved, we needed to propose 12 problems in total .

UPD: Score distribution: $$$500-1000-1250-1750-2250-2750$$$

We would like to thank:

• darkkcyan for incredible coordination and help with the problem preparation
• Alexdat2000 for the Russian translations and precious help regarding the statements and limits
• KAN for upgrading the quality of statements
• Gary2005, awoo, Huah, feecle6418, vinfat, marvinthang, Psychotic_D, tolbi, Black_Be4rD, Hasnaine_, tanus_era, thisIsMorningstar, __FaRiA_eFa__, masood_, Ryu204, badlad, TomiokapEace and ayhan23 for testing this round and providing valuable feedbacks
• MikeMirzayanov for the amazing Codeforces and Polygon platforms
• You, for participating in this round

This is our first round! We've tried our best to make the round enjoyable. It is greatly recommended to read all the problems.

We are looking forward to your participation. Good luck to everyone .

UPD2: Congratulations to the winners!

Overall:
1. jiangly
2. SSRS_
3. Geothermal
4. BurnedChicken
5. Ormlis

Div. 2:
1. CoCl2_6H2O
2. Joyemang
3. gqh_cpp
4. rainboy
5. NoMentalPowerLeft

UPD3: Editorial is out

Greetings, CodeForces!

jiangtaizhe001, qzhwlzy and I rsj are more than excited to invite you to participate in TypeDB Forces 2023 (Div. 1 + Div. 2, Rated, Prizes!), which starts on Jan/29/2023 17:35 (Moscow time).

The round is open and rated for everyone. You are given 9 problems, no subtasks or interactive problems, and you have 3 hours to solve them. It is recommended to read all problems. The statements were made as briefly and clearly as we could. Enjoy the contest!

UPD: Score distribution: $$$500-1000-1750-2000-2250-2500-3250-3500-3750$$$

Sincere thanks to:

• 74TrAkToR, for a long-term, tough and perfect coordination.
• qzhwlzy, for writing and polishing statements and tutorials, and sparky ideas.
• jiangtaizhe001, for helping me a lot in preparation.
• 275307894a and A_zjzj, for providing wonderful problems and solutions.
• carnation13, willy108, NemanjaSo2005 and EverlastingEternity for great suggestions to the problems.
• NemanjaSo2005, EverlastingEternity, plagues, WGYHMFkZyA02, xiongyushun, dorijanlendvaj, AlexLuchianov, Gary2005, SSerxhs, RUSH_D_CAT, Lavine, Kieray, Alice114514, Atziluth, Depth_First_Search, OdtreePrincess, A_zjzj, _WD_, 275307894a, Electric_Field, carnation13, Hanriver, some_idiot, willy108, gamegame, Pointy, Huah, ShmilyTY, njupt_lyy, E_huan, p_b_p_b, jjjjssss6, HolyK, -skyline- and Isla81920, for testing the contest and providing useful feedback.
• MikeMirzayanov, for the great systems Codeforces and Polygon.

Thanks to Vaticle's sponsership, winners will receive awesome prizes!

Cash and Swag Prizes

• 1st place: 500 Euros
• 2nd place: 250 Euros
• 3rd place: 100 Euros
• Top 50: TypeDB hoodie, t-shirt and stickers
• Random 50 of 51-250: TypeDB t-shirt and stickers

About Vaticle & TypeDB

Vaticle is a team of people driven to empower engineers to solve complex problems. We are the creators of the strongly-typed database, TypeDB, and its query language, TypeQL. You can find out more about our work from another announcement post, interview post, our website and GitHub pages. You can also apply directly to our team using the button below:

UPD1: Editorial

UPD2: Congratulations to the winners:

• ko_osaga
• tourist
• Radewoosh
• Benq
• ecnerwala

Hello! Codeforces Round 847 (Div. 3) will start at Jan/27/2023 17:35 (Moscow time). You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

You will be given 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round is 10 minutes.

Remember 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)
• 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, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of our work. Problems have been created and written by ITMO University team: MikeMirzayanov, myav, Gol_D, Aris, Gornak40, senjougaharin and Vladosiya. Also this time, molney suggested one of the tasks.

We would like to thank: alwyn, morasha3, csegura, BledDest, stevenkplus, Darko, Coki628, Crutch, Qwerty1232, Jostic11, liouzhou_101, Jeffin, AW_Flister, glebustim, yorky, mango_lassi, 74TrAkToR, ErrorDeveloper, Be_dos, MODDI, Vercingetorix for testing the contest and valuable feedback. List of testers will be updated.

Good luck!

UPD: Editorial

Hello, Codeforces!

IzhtskiyTimofey, qualdoom and I are glad to invite everyone to participate in Codeforces Round 846 (Div. 2), which will take place in Jan/25/2023 17:35 (Moscow time).

This round will be rated for the participants with rating lower than 0x834 (i.e. 2100). Participants with a higher rating can take part in the round unofficially.

You will have 7 tasks and 2 hours to solve them.

One of the problems will be interactive. Make sure to read this blog and familiarize yourself with these types of problems before the round!

I want to sincerely thank everyone who provided invaluable help in preparing the round and made it many times better:

• 74TrAkToR for rejection of 10+ tasks an idea for a problem, help in preparing the round and excellent coordination!

• KAN for upgrading the quality of statements.

• blobugh, maomao90, maks_matiupatenko, loggerr, vdv09, alex.kudryashov, FynjyBath, alexey.shchepin, Alcabel, induk_v_tsiane, Siberian, polosatic, FedShat and tryharder for testing the round and useful feedback!

• MikeMirzayanov for Codeforces and Polygon platforms!

• You for participating in this round.

This is our first official round on Codeforces. We sincerely hope to your participation. We hope that you will like the proposed tasks!

The score will be announced closer to the start of the round.

We wish you good luck and have a good time! See you in the round!

UPD: Scoring distribution: $$$500-1000-1250-1500-1750-2000-2500$$$

UPD: Round is unrated. We're sorry — it's our fault.

UPD: Tutorial and comment about task C Once again, we apologize for the inconvenience caused.

Hello, everyone!

We look forward to our upcoming competition — TypeDB Forces 2023 (Div. 1 + Div. 2, Rated, Prizes!), which will take place on Jan/29/2023 17:35 (Moscow time). In the meantime, you can learn a little more about us.

We’re from Vaticle, and we’re the creators of TypeDB & TypeQL. All members of our team are unique and talented, and today we want to introduce you to one of them.

How would you introduce yourself?

I'm Krishnan, I grew up in India and spent a little too much time on the internet and fiddling with my (underpowered) PC. After completing my Bachelor's degree, I spent a year as a software engineer working on a huge data lake, the next as a research fellow trying to permute thread executions to force out concurrency bugs, a year doing a masters with a focus on the old-style AI (and logic-programming). After a short-lived attempt at a Ph.D., I'm now at Vaticle working on the automated reasoning built into our database.

When did you start Competitive Programming?

Probably in my second year of uni. One of my friends decided it would be fun and we just started doing contests. Later on, another friend convinced me to learn a bit more and join his ICPC team. The discussions I had with him were great.

What have you since learned and how has competitive programming impacted your skills?

Everyone reading this knows better than me, but CP has made me a lot better at dissecting a problem better and isolating the crux of it. It also makes you great at coming up with the simplest possible implementation which covers all the (edge) cases. The clarity of thought you need to get an AC is something I would have taken much longer to develop without it.

What is it like working at TypeDB as an Engineer?

The problems you get to work on here at Vaticle are great fun. There's a nice balance of freedom to explore solutions and expectations on output- so you're happy with the state of whatever you're building. It feels like a good time to be at the company because we're stable enough to know what we want to do and have some idea of how we want to do it, but still early enough that you have to define and drive the solution.

Another great thing is the variety of fields we touch on in our work — There's something in it for almost everyone. The query language and type system design, the semantics of the language, the graph traversal algorithm, the storage engine, and its low-level data structures, and the distributed systems aspect to scale it all up. We even have our own IDE (and a very, very cool graph visualizer). You also have to dive into the internals of programming languages, build systems, and cloud infrastructure.

To top it all off, with the group of extremely smart people working here and their varied interests, you have a lot of great (and often tangential) discussions in the meeting room, the lunch table (and the pub). Even so, I think we could do with a few more competitive programmers in the team ;)

What kind of problems are you working on?

The focus of my work is the reasoner (which sits well with my interest in logic programming). The first major piece of work here was the resolution planner – what is the best order to evaluate a recursive query? The discussions with my colleagues were critical to making heads or tails of the problem. It could still use some work though (anyone like decomposing graphs?)

I've since worked on adding arithmetic & aggregate queries into the system — which involved finding the right conceptual model to think about all these in a graph setting. We've had some great discussions on the various database models and how it fits into their systems.

The next chunk of work I look forward to is to tame the reasoner a little more. The current solution is very elegant — it's simple and powerful as a direct result of its simplicity. We just need to add a few missing properties to the resolution procedure to bring it up to the state of the rest of the system.

The data in knowledge graphs tend to be highly interconnected, and we know interconnectedness is a recipe for hard problems.

So, if you already want to become a member of our team, then without delay fill out this form. But, if you need more details about us and our work, we invite you to our website and GitHub pages.

Hello Codeforces!

On Jan/24/2023 17:35 (Moscow time) Educational Codeforces Round 142 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

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, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

Hey, Codeforces!

Preparations are under way for the second “Hello Muscat 2023” ICPC programming bootcamp, the continuation of the “Hello” bootcamp series, organised by Harbour.Space University, in collaboration with PhazeRo, Gutech, UK Oman Digital Club, Leagues of Code, Gutech CS Club and Codeforces!

Quite exciting, isn’t it? Now it's time for you to dive deeper into the competitive programming world with the 8 days intensive Hello Muscat 2023. It will take place in Muscat, Oman and online from March 8th to March 16th, 2023, both participation formats are available. As always, we can’t wait to see you there to learn, practice and compete on the international stage, smoothing your road towards the joined World Finals 2022 and 2023 in Egypt!

Our coaching line-up combines talent and experience, featuring ICPC world champions winners and finalists, as well as legendary names from the field of competitive programming: Mike Mirzayanov MikeMirzayanov, Yahor Dubovik 244mhq, Artem Plotkin Rox, Maksym Oboznyi MaksymOboznyi and Nikolay Budin budalnik.

The Bootcamp will be split into three divisions:

• Division A. Division A will be a mirror of the Petrozavodsk Programming Camp. Suitable for teams who already qualified for the world finals ICPC or are aiming that high.
• Division B. Designed to help teams prepare for the next season of ICPC regional competitions. Appropriate as an introduction for teams and students just getting their foot in the door of the world of ICPC and competitive programming competitions in general.
• Division C. Designed for newcomers to the world of ICPC competitive programming.

Types of participation: On-Site and Online

_We believe that participation in our Bootcamp should be accessible by all teams wherever they are and that is why we made onsite and online types of participation. 20% Early Bird Discount is offered to universities and participants who register and pay before Jan 31st 2023.

• On-site:

Price: 1500 € — 1200 €

What is included: training, contests, access to the recordings of the lectures, accommodation for 9 nights in a 4 star hotel Mysk, breakfast and lunch, transfer from hotel to venue every day, leisure, entertainment and welcome pack.

• Online:

Price: 100 € — 80 €

What is included: training, contests, access to the recordings of the lectures.

Good luck with the round!

UPD: Editorial is out