Hello Codeforces!

On Oct/29/2021 17:35 (Moscow time) Educational Codeforces Round 116 (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, Roman Roms Glazov 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:

Hello once again, Codeforces!

We are excited to anounce, the "Hello" Bootcamp series is back. After postponing the 2020 event due to Covid-19, this year's bootcamp will take place online, making it more accessible and affordable for competitive programmers worldwide.

Divisions

Our mission is to make competitive programming accessible to everyone. To help us achieve this mission, we are making our bootcamps available to teams of different skill levels – separated by two divisions of difficulty:

Division B: Designed to help teams prepare for the next season of ICPC regional competitions.

Division C: Designed for newcomers to the world of ICPC competitive programming.

We are inviting all of you to join us online, from 4 to 12 of December 2021 for 8 days of intense programming.

আবার চলে এসেছি! (That's Bengali for "I am back! (in Terminator mode)")

I am super excited to invite you to participate in Codeforces Round #752 (Div. 1) and Codeforces Round #752 (Div. 2) which will be held on Oct/30/2021 17:35 (Moscow time). This round is rated for both divisions.

You will be given $$$6$$$ problems in each division and $$$2$$$ hours to solve them. All the problems are authored and prepared by me.

I would like to thank -

• antontrygubO_o for his breathtaking(literally) coordination of the round. no funny text this time
• Alpha_Q, Anachor and antontrygubO_o for putting up with my dumb ranting and helping with the problems.
• Um_nik, gamegame, kefaa2, dorijanlendvaj, upobir, _Ash__, Anachor, Arg_007, Alpha_Q, steinum, Tasdid, t17, imAnik, Alfeh, Aritra741, SajidZakaria, YoyOyoYOy000y000, SlowDecay, ijxjdjd, flamestorm, ovis96, chctxdy68, and Urvuk3 for testing the round.
• dorijanlendvaj for providing a test case which will potentially prevent few wrong solutions from getting AC.
• The great MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• You, for existing and participating in the round. Also, thanks for giving your best and not quitting. You will eventually be happy . Just hold right there.

The statements are short and directly ask you what to do and I have tried to make the pretests strong. I highly encourage you to read all the problems.

Solve problems and help the poor! Yes, you heard it right, this time you can help the world by just solving problems. I will donate money based on the solve count of each problem by the following measure:

Div2A - 0.005 USD
Div2B - 0.005 USD
Div2C/Div1A - 0.005 USD
Div2D/Div1B - 0.01 USD
Div2E/Div1C - 0.04 USD
Div2F/Div1D - 0.2 USD
Div1E - 2 USD
Div1F - 4 USD

The total estimated money is half of what I will get from Codeforces for this contest(but you can make it more by just solving more problems!). I am a student, so pardon me if that's too little.

Also, did you know that you can still upvote my The Ultimate Topic List blog and make it to the top?

Finally, I would like to dedicate this contest to me! I want to thank me for believing in me, for doing all this hard work, for trying to do more right than wrong. I want to thank me for just being me at all times.

Score distribution:
Div.1: $$$750-1000-1750-2500- 3500-3750$$$.
Div.2: $$$500-1000-1750-2000-2750-3500$$$.

Good Luck! Love you .

Hi everybody,

This Sunday there will be a XIX Moscow Team Olympiad, high school students competition based in Moscow that is an elimination contest for All-Russian Team Olympiad. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Open Olympiad, Moscow Olympiad for Young Students and Metropolises Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583, 594, 622, 626, 657, 680, 704, 707, 727).

The round will be held at Oct/25/2021 09:35 (Moscow time) and will last for 2 hours. Note the unusual time of the round. Each division will have 6 problems. The round will be held according to the Codeforces rules and will be rated for both divisions.

We kindly ask all the community members that are going to participate in the competition to show sportsmanship by not trying to cheat in any manner, in particular, by trying to figure out problem statements from the onsite participants. If you end up knowing some of the problems of Moscow Team Olympiad (by participating in it, from some of the onsite contestants or in any other way), please do not participate in the round. We also ask onsite contestants to not discuss problems in public. Failure to comply with any of the rules above may result in a disqualification.

Problems are prepared by LHiC, cdkrot, isaf27, AlesyaIvanova, Tikhon228, voidmax, fedoseev.timofey, KiKoS, NiceClock, 4eT_llpuyHblJl, vintage_Vlad_Makeev and Daria Krokhina under my supervision with great help of GlebsHP, meshanya, Endagorion, Zlobober and Helen Andreeva.

Thanks to adedalic and KAN for the round coordination and verifying statement of original olympiad, adedalic and GlebsHP for statement translation, and also thanks for MikeMirzayanov for systems codeforces and polygon, which was used to prepare problems of this olympiad.

Also thanks to napstablook and Anti-Light for providing an additional problems that helped to create (I hope) a balanced problem set for the round

Good luck everybody!

UPD1: Thanks to Um_nik, PurpleCrayon, LHiC, VladaMG98, JovanB, TadijaSebez, AlanSkarica, Markadiusz, algorithm16, jurichhh8 for testing.

UPD2: Scoring distribution:

Div.1: 500 — 1250 — 2000 — 2250 — 2250 — 3000

Div.2: 500 — 1000 — 1500 — 2250 — 3000 — 3250

UPD3: Editorial

UPD4: Winners!

Div. 1:

1. djq_cpp
2. ksun48
3. maroonrk
4. ko_osaga
5. Radewoosh

Div. 2:

1. zero4338
2. C2020jzm
3. SYDevil
4. CQBZ_PPL
5. just_ice

Hello, Codeforces!

74TrAkToR and I are glad to invite you to our Codeforces Round #750 (Div. 2), which will be held at Oct/24/2021 13:05 (Moscow time). Notice the unusual time of the round. The round will be rated for all the participants with rating strictly less than 2100. At the time of the round the CheReKOSH olympiad will be held, where the problems from this round will be used!

We would like to thank everyone who helped us a lot with round preparation.

• Our coordinators KAN and isaf27 for excellent coordination of the round.
• Our testers Um_nik, Denisson, TadijaSebez, ijxjdjd, Mr.Robot_28, flamestorm, romanasa, hu_tao, QuangBuiYT, m371 for high-quality testing and helpful notes.
• MikeMirzayanov for amazing Codeforces and Polygon platforms.

On the round you will be asked to help characters from animated series Luntik and his friends. You will be given 7 problems, one of which has two subtasks. You will have 2 hours 30 minutes to solve them.

UPD: Score distribution: $$$500-750-1500-1750-2500-(2000+1500)-3250$$$.

UPD2: Editorial

UPD3: Congratulations to the winners!

Div. 2:

1. int65536

2. hehezhouyyds

3. trunkty

4. m3owp1mp

5. Chtholly-Nota-Seniorious

Div. 1 + Div. 2:

1. SSRS_

2. emthrm

3. int65536

4. turmax

5. hehezhouyyds

We wish everyone good luck!

Hi all!

This weekend, at Oct/17/2021 14:05 (Moscow time) we will hold Codeforces Round #749 (Div. 1 + Div. 2, based on Technocup 2022 Elimination Round 1). It is based on the problems of Technocup 2022 Elimination Round 1 that will be held at the same time.

Note the unusual start time of the contest.

Technocup is a major olympiad for Russian-speaking high-school students, so if you fall into this category, please register at Technocup website and take part in the Elimination Round.

The Div. 1 + Div.2 edition is open and rated for everyone. Register and enjoy the contests!

The problems were written and prepared by Tlatoani, golions, rabaiBomkarBittalBang, qlf9, and me. We would like to express our thanks for antontrygubO_o, isaf27, and KAN for reviewing our problems and being great coordinators!

Huge thanks to the following users for testing our round: kefaa2, AmShZ, dorijanlendvaj, Keshi, czhang2718, 2020akadaver, Magikarp1, Richw818, quantum8, RayLee234, I_Love_YrNameCouldBeHere, Qualified, 1-gon, smax, m371, kassutta, namanbansal013, HackerMonk, Ari, PurpleCrayon, FieryPhoenix, Jellyman102, bWayne, Omkar, Aleks5d, Makcum888

And as usual, thanks to MikeMirzayanov for the great Codeforces and Polygon platforms.

You will have 2 hours and 15 minutes to solve 9 problems. The score distribution will be announced very shortly before the contest starts. Good luck to all!

UPD1:

Score distribution: $$$500$$$ — $$$1000$$$ — $$$1500$$$ — $$$1750$$$ — $$$2250$$$ — $$$2750$$$ — $$$3000$$$ — $$$3500$$$ — $$$4000$$$.

UPD2:

Thanks to everyone who participated in the contest! We hope you enjoyed the problems. We apologize for the issues at the beginning of the contest; we hope that you were still able to have a great experience.

Editorial

UPD3:

Congratulations to the winners of Codeforces Round #749 (Div. 1 + Div. 2, based on Technocup 2022 Elimination Round 1)!

1. medium_waxberry
2. fivedemands
3. jiangly
4. peti1234
5. xay5421
6. Um_nik
7. orzdevinwang
8. yosupo
9. SHZhang2
10. tatyam

And a special congratulations to peti1234 for being the only contestant to solve problem I!

Congratulations also to the winners of Technocup 2022 - Elimination Round 1!

1. Ormlis
2. SomethingNew
3. Arayi
4. alexxela12345
5. I_HATE_CONSTRUCTIVES
6. oleh1421
7. Mangooste
8. arbuzick
9. idontwannawin
10. Dasha_Gnedko

Hello, Codeforces.

Please, welcome c++20 support on Codeforces. Yes, it is 64-bit. Thanks to Brecht Sanders: I used his distribution GCC-11.2.0-64 from https://winlibs.com/.

If you have installed PBOX, you can add this compiler with the line pbox install gcc11-64-winlibs. Probably, a good idea is to add C:\Programs\gcc11-64-winlibs\bin into the PATH. More about PBOX you can read here.

I use the compilation command line similar to other GCC installations: g++ -Wall -Wextra -Wconversion -static -DONLINE_JUDGE -Wl,--stack=268435456 -O2 -std=c++20 <source>. The only differences are -std=c++20 and -Wall -Wextra -Wconversion (I plan to use somehow such warnings in Polygon to suggest fixes in uploaded files).

Now you can use c++20 in your solutions. I'm not sure there are many features useful in competitive programming. Probably, I'm wrong. For example, now you can write vector v{vector{1, 2}}; instead of vector<vector<int>> v{vector<int>{1, 2}};. What else is useful? Please, if you are good with modern C++ then write.

You might be interested in looking at such a table. Before implementation, I always test every C++ distribution for the efficiency of reading and writing large amounts of data. For example, the latest GCC compiler from MSYS2 is terribly slow in some cases. I don't want to use it here. Also, it happens that some specifiers like lld or Lf work unexpectedly. In the table by reference, the second line is the added compiler. The columns correspond to different tests. The cell contains the time of the test execution. If I have time, I will someday publish scripts for testing c++ compiler installations.

Bye for now,
— Mike

Hello, Codeforces!

I'm glad to invite you to amazing (we've tried to make it such) Codeforces Round #748 (Div. 3) which will start on Oct/13/2021 17:35 (Moscow time). This round is made by me (MrPaul_TUser), a significant contribution to the round was also made by MikeMirzayanov and BledDest.

The round contains 6-8 problems. The difficulties of the problems are expected 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 1600 or higher, can register for the round 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 tried to make really strong tests — just like you will be surprised if many solutions fail after the contest is over.

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

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) 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 trusted participants of the third division, you must:

• take part in at least two 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 _c_k_r_, Vladosiya, spotless, Yousry, powergee101, ncduy0303, I_Remember_Olya_ashmelev, A_Killer, OlegZubkov, mahade31, arjunsanjeev7, and UpS0lver for testing the round and improving tasks.

Good luck and have fun!

UPD Editorial