Hi everyone!

I would like to invite you to my second Codeforces round, which I have created with my friends Ashishgup and Vivek1998299.

With that said, I bring to your attention our new Codeforces Round #548 (Div. 2) that will take place on Mar/21/2019 18:35 (Moscow time). If your rating is less than 2100, this round will be rated for you; otherwise, you can participate out of competition.

I would like to thank Ashishgup and Vivek1998299 for their help with preparing problems and _kun_ for coordinating our round. I would also like to thank MikeMirzayanov for the awesome Codeforces and Polygon platforms.

You will be given 6 problems and 2 hours to solve them. Scoring distribution will be announced later.

Good luck! :D

UPD1: Shortly after the contest, we'll be on the community Discord server to discuss the tasks.

Hello, Codeforces!

I am pleased to invite you to Codeforces Round #547 (Div. 3), which will start on Mar/19/2019 17:35 (Moscow time). Everyone whose current rating is strictly less than 1600 is invited to participate officially. All others can take part out of the competition.

It so happened that the schedule of this month is not replete with rounds (coordinators, we hope for you!). Therefore I decided to partially correct the situation. All the problems of this round were invented and prepared by me on the last day of Hello Muscat Programming Bootcamp 2019 and on flights from Muscat to St. Petersburg. I even specially noted the time for preparation: for the current moment (the problems are ready for testing) I spent about 6 hours on their preparation, including inventing some of the problems. I really like working on problems, this is something at the intersection of creativity and programming. I really hope you enjoy the result of my work.

I am in Oman while writing the problems for the round.

The round will be hosted by rules of educational rounds (extended 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. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over. You will be given 6-8 problems for 2 hours to solve them.

Note that the penalty for incorrect submissions 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 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.

I hope a little later a list of thanks to testers will appear instead of this paragraph. So far I only plan to give the round to testing. Many thanks to the testers ivan100sic, KrK, Benq, I_love_Tanya_Romanova, nhho! UPD: And extra thanks to more testers Pavs, PikMike, Narts, anon20016, Stresshoover, Ivan19981305.

Good luck on the round
— MikeMirzayanov

Hello!

We supported the rendering of LaTeX-formulas with MathJax in new posts and comments. Now the formulas will be as beautiful as in problem statements. Drawback: they are displayed not immediately, but redrawn after the page is displayed. Old posts and comments are displayed in the old way (already a lot of old content, backward compatibility is very important). Note that if you edit old post, it will still be displayed in the old style.

Here are some example: $$$1 \le n \le 10^{12}$$$,  $$$c = \sqrt{a^2+b^2}$$$,  $$$i\hbar\frac{\partial}{\partial t}\left|\Psi(t)\right>=H\left|\Psi(t)\right>$$$.

Hi, Codeforces!

I`m glad to invite everybody to the #546 Codeforces round, which will be held on Monday, March 11, 2019 at 19:35. The round will be rated for all participants from the second division (with rating below than 2100). As usually, we will be glad to see participants from the first division out of competition!

Problems for the round have been proposed by Fedor osaaateiasavtnl. Ushakov, Stepan IbragiMMamilov Stepkin, Alexey usertab34 Roze, Denis Denisson Shpakovskij and Alexander Ralsei Gladkov.

The round have been prepared by us, Dmitry DmitryGrigorev Grigoryev, Fedor osaaateiasavtnl. Ushakov, Semyon cookiedoth Savkin and Dmitry TheWayISteppedOutTheCar Piskalov.

We'd like to give thanks to Ildar 300iq Gainullin for excellent coordination of the round, Grigoriy V--gLaSsH0ldEr593--V Reznikov, Alexey Aleks5d Upirvitsky and Mohammed mohammedehab2002 Ehab for testing and to Mike MikeMirzayanov Mirzayanov as well for his unbelievable Codeforces and Polygon platforms.

You will receive 5 problems and 2 hours for solving it. During the round you will be helping for an extraordinary girl Nastya, who is studying in an usual school in Byteland.

Score distribution will be announced, traditionally, closer to the start of the contest.

Please, read all the tasks. Good luck!

UPD Score distribution is standart — 500-1000-1500-2000-2500

We're looking forward your participation.

UPD2 Thank you for your participation in the contest!

List of the winners of the contest:

Div.2

1. woookje

2. 1021869

3. StasyaCat

4. Hamzqq9

5. ilyausmanov

Div.1 + Div.2

1. kmjp

2. step_by_step

3. TangentDay

4. ..vince

5. hitman623

My frank congratulations for all the winners!

The editorial will be posted very soon. We apologize for delay.

UPD3

The editorial

Hello!

Right now happens the first tour of the Open Olympiad in Informatics, and tomorrow will be the second one. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Team Olympiad, Moscow Olympiad for Young Students and Metropolises Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541)

Open Olympiad consists of the most interesting and hard problems that are proposed my a wide community of authors, so we decided to conduct a Codeforces regular round based on it, which will happen Mar/08/2019 12:05 (Moscow time) and will be based on both days of the Olympiad. Each division will have 6 problems and 2:30 hours to solve them.

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 Open 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 of this competition were prepared by V--gLaSsH0ldEr593--V, isaf27, Flyrise, _kun_, GlebsHP, ch_egor, Zlobober, qoo2p5, grphil, achulkov2, Schemtschik, akvasha, mingaleg, V--o_o--V, wrg0ababd, guided by ch_egor, _kun_, GlebsHP, Zlobober and Helen Andreeva.

Problems for second division were prepared by KAN and MikeMirzayanov, to who we also want to say thanks for the Codeforces and Polygon systems.

Good luck everybody!

UPD: Congratulations to the winners!

Div.1

1. sunset
2. Petr
3. Radewoosh
4. ko_osaga
5. orbitingflea

Div.2

1. appplese
2. al3xstr33t
3. Charlene_Hao
4. ytxytx
5. QDEZ604

The editorial will appear soon

UPD: The editorial

<copy-pasted-part>

Hello! Codeforces Round #544 (Div. 3) will start at Mar/07/2019 18:05 (Moscow time). You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. Probably, participants from the first division will not be at all interested by this problems. And for 1600-1899 the problems will be too easy. However, all of you who wish to take part and have 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. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 6 or 7 (or 8) problems and 2 hours 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 a 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 MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work. Thanks to my good friends Mikhail PikMike Piklyaev, Maksim Ne0n25 Mescheryakov and Ivan BledDest Androsov for help in round preparation and testing the round.

Good luck!

I also would like to say that participants who will submit wrong solutions on purpose and hack them afterwards (example) will not be shown in the hacking leaders table.

</copy-pasted-part>

UPD0: I also would like to thank Stresshoover, dreamoon_love_AA, Nebuchadnezzar and nhho for help in testing the round!

UPD1: Editorial is published!

UPD2:

Congratulations to the winners:

Congratulations to the best hackers:

And finally people who were the first to solve each problem:

The 9th BSUIR Open Programming Championship will be held from March 13 till April 25, 2019 (Minsk, Belarus).

Hello Codeforces!

On Mar/05/2019 18:05 (Moscow time) Educational Codeforces Round 61 (Rated for Div. 2) will start.

This round is organised in collaboration with Hello Muscat Programming Bootcamp and supported by Sberbank, General Partner of the boot camp and one of the largest banking leaders of Eastern Europe, providing thousands of jobs and innovation in the financial industry.

As the Hello Muscat Programming Bootcamp’s General Partner, Sberbank made it possible for students from some of the world’s top universities to attend the bootcamp, by sponsoring their participation. This includes students from Saint-Petersburg State University, Moscow Institute of Physics and Technology (MIPT), Penza State University, National Research Mordovia State University; MRSU, ITMO, Higher School of Economics / Moscow, Volgograd State Technical University, Lobachevsky State University of Nizhni Novgorod, Moscow Aviation Institute, Tyumen industrial University, University of Haifa, Northern (Arctic) Federal University, Saratov State University, Ural Federal University.

Hello Muscat Bootcamp will take place from 9th to 15th of March, and 120 students from 24 universities, including MIPT, Saint Petersburg State University and University of Tokyo will compete and practice side-by-side, smoothing the road towards the April World Finals in Porto.

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 7 problems and 2 hours to solve them.

The problems were invented and prepared by Roman Roms Glazov, Adilbek adedalic Dalabaev, Vladimir Vovuh Petrov, Ivan BledDest Androsov, Maksim Ne0n25 Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all participants!

Congratulations to the winners:

Congratulations to the best hackers:

And finally people who were the first to solve each problem:

UPD: Editorial is out

Hello everyone!

The Final Round of Technocup 2019 starts today, on the March 3, 2019 at 11:00 MSK (08:00 UTC)! To watch live results (only pretests are considered!), follow the link below:

Results of Technocup 2019 Final Round

Congratulations to the winners of Technocup Final Round 2019!

1. Ildar 300iq Gainullin, Russia, Kazan'
2. Semyon cookiedoth Savkin, Russia, Dolgoprudnyy
3. Batyr Batrr Sardarbekov, Kazakhstan, Almaty
4. Alexander scanhex Morozov, Russia, Saint Petersburg
5. Sofia Sonechko Melnyk, Ukraine, Kremenchuk

For those who want to compete on the same problems, we will hold two regular Codeforces Rounds in the evening: one for the first division, and another one for the second. The rounds are starting at Mar/03/2019 18:35 (Moscow time)!

If you are a participant of the official Technocup Finals, you are not allowed to take part in the rounds at evening. We ask participants of the official Finals not to discuss the problems in open media till evening.

Good luck!

The rounds are over. We sincerely apologize for the fail with the mirror rounds, we thought the editorial was only streamed to other sites of the olympiad, not online. You can read MikeMirzayanov's comment about the situation. I hope you enjoyed solving the problems even though they did not affected your rating.

Huge thanks to those people who worked on the problems for you, namely Alexander Golovanov399 Golovanov, Konstantin zemen Semenov, Daria Dashk0 Kolodzey, Mikhail Endagorion Tikhomirov, Ilia irkstepanov Stepanov and Denis Denisson Shpakovskij.

Also thanks to Um_nik, adedalic, demon1999, Roms, _kun_, cyand1317, BledDest and Errichto for testing the problems, arsor for translating some of them into English, and _kun_ and arsijo for their help in conducting the mirror rounds.

Congratulations to the winners of the mirror rounds!

Codeforces Round #543 (Div. 1, based on Technocup 2019 Final Round)

1. Radewoosh
2. LHiC
3. V--gLaSsH0ldEr593--V
4. natsugiri
5. V--o_o--V

Codeforces Round #543 (Div. 2, based on Technocup 2019 Final Round)

1. Diazzz
2. IhateProgramming
3. Kunal.h
4. galloska
5. deep_savani

Microsoft's Quantum Team and Codeforces are excited to invite you to Microsoft Q# Coding Contest — Winter 2019!

The contest will run from March 1 to March 4 and will offer increasingly challenging tasks on superposition, measurement, quantum oracles and unitary transformations.

As a reminder, last weekend we held a warmup round with easier tasks on quantum oracles and unitary transformations; the tasks are available for practice here, and the solutions are explained here. You can brush up on the topics of superposition and measurement in the first Q# contest and its warmup round.

Several useful reminders:

• The contest is unrated :-)
• Solutions are accepted only in Q#.
• Participants are ranked according to the number of correctly solved tasks, with the last correct submission time as a tiebreaker.
• The tasks are grouped by topic, and the tasks within one topic are ordered in approximate order of increasing difficulty. If you find a problem too hard, don't forget to check the next problems in this topic and problems from different topics, they might turn out to be easier.
• Submission verdicts work as follows:
  Wrong Answer means that the solution fails any problem-specific checks (such as leaving the qubits in a state other than expected, using measurements in a task which prohibits them or returning incorrect classical value in measurement tasks) or prints anything to the standard output (using Message or DumpMachine functions);
  Runtime Error means that the solution throws a more general exception (for example, caused by releasing allocated qubits in non-zero state or trying to access array elements outside of array bounds);
  Memory Limit Exceeded means that the solution together with the checker allocated more qubits than it is allowed (the limit is ~15 qubits for problems related to quantum oracles with memory limit 1024MB, and ~25 qubits for other types of problems);
  Time Limit Exceeded works the same way as in classical competitions (your program is too slow), but I have to mention it for the sake of completeness :-)
• Custom Invocation allows you to run Q# code on Codeforces servers; make sure your code has namespace Solution and an operation with a signature operation RunQsharp () : Bool defined in it.
• And finally, the really important stuff: the top 50 ranked participants will receive a Microsoft Quantum T-shirt! Here is a preview: