Recently I returned from the Workshop and wanna share my impressions.

The post will be divided into several parts depending on an aspect I am covering in it.

(original)

Hello everyone!

CF round #333 (both divisions) is going to take place today. The authors of this round are me and Baklazan.

By total coincidence, I'm the author of even-indexed problems and Baklazan the author of odd-indexed problems. Now I'm going to let you wonder if it's 0-based or 1-based :D.

As usual, thanks to GlebsHP for his help (in particular, helping us not overkill the problems), MikeMirzayanov for CF and Polygon, Delinur for problem statement translations and our testers: misof, Mimino, AlexFetisov and winger.

I wish good results and rating changes to those who earn it, as well as a zero-sum rating update to everyone.

Score distribution:

Div. 2: 500-1000-1500-2250-2250

Div. 1: 500-1250-1250-2000-2500

Winrars:

Div. 1

1. jqdai0815

2. JoeyWheeler

3. rng_58

4. PavelKunyavskiy

5. mnbvmar

Div. 2

1. liuyibo

2. Mi_Sawa

3. HeartBeats

4. marian.darius

5. EasyRed29

(homogeneous colours :D)

Hi, Codeforces.

I am happy to say that Codeforces Round #332 (Div.2) will take place November 20th at 19:35 MSK. This is my second Codefocres round and I hope not the last.

Thanks a lot to Dmitry Rozhkov (rui-de) for solving these problems, also thanks to Vlad Vishvevski (Vladik) for cool pictures. I'd like to thank Gleb Evstropov (GlebsHP) for help in round preparation. And, as usual, big thanks to Maria Belova (Delinur) for statement translation and to MikeMirzayanov for such great systems as Codeforces and Polygon.

The duration of the contest is two hours. What about tasks, it's not a secret that you can find Spongebob's pineapple and a restaurant with strange name "Crasti Crabs", cosy beach and Jellyfish Meadows on the bottom of the ocean. Spongebob and his friends need in your help, help them!

I strongly recommend you to read all the problems and, probably, you will find something right for you.

As usual, scoring distribution will be announced later.

UPD: Score distribution — 500 — 1000 — 1500 — 2000 — 3000.

Editorial.

Div. 2 Winners

jerjerismygf

rakhashov.maksat

jeremy624lolz

Div. 1 Winners

MrDindows

anta

ngfam_kongu

Congratulations!

Hello, Codeforces!

I am happy to announce Codeforces Round #331 (Div. 2)! The round will be held on November 15th at 7:35 MSK. Div. 1 users can participate out of contest.

The problem set was prepared by me (Girishvar Venkat) and jaina (Jeffrey Zhang). I sincerely thank GlebsHP (Gleb Evstropov) for helping with the preparations of the contest. I also thank thesilione (Bili Sun) for testing this round.

The hero for this round will be Wilbur the pig, after my good friend wilbs43 (Wilbur Li).

Scoring will be 500-1000-1500-2250-2500.

Hope you enjoy this round and wish you high rating!

UPD: Contest is over. Here is a link to editorial: Editorial.

UPD2: Congratulations to all the winners! Results:

Div. 1:

1. tourist

2. DBradac

3. ztxz16

4. V--o_o--V

5. waterfalls

Div. 2:

1. Ichiban

2. Antoniuk

3. thjchph4trjnh

4. halyavin

5. Rafiki53

Hope you all enjoyed this contest! Thanks for participating!

UPD3: Ratings updated.

Educational Codeforces Round 1 is over. During 24 hours after coding phase many of you tried to hack other's solutions. And it were many successful hacks!

It was 573 successful hacks, made by 101 hackers. Here are most effective:

Thank you! Now I'm pretty sure that tests of this problems are really complete. Moreover hacks shown that writer's tests are often incomplete. In short, it seems it was really good idea to make open hacks phase.

I'd like to crowdsource editorial for such rounds. Please, write in comments if your are ready to write/improve a editorial for problems C-F. For sure, you should solve problem to help with editorial.

Please, write in comments your feedback. It is very important for us to get it. Thanks!

Hi all!

On September 13, a qualification contest for ACM ICPC was held in Samara SAU. We always put our contests to Codeforces Gyms, so this Saturday, November 14, 11.00 MSK everyone will be able to enjoy it.

The contest will be held at Codeforces Gyms, it will be unrated and will last for 5 hours. The problems were prepared by craus and Shlakoblock.

And here is the full list of our previous contests:

• 2012, V Samara Regional Intercollegiate Programming Contest
• 2012, Samara SAU ACM ICPC Quarterfinal Qualification Contest
• 2013, VI Samara Regional Intercollegiate Programming Contest
• 2013, Samara SAU ACM ICPC Quarterfinal Qualification Contest
• 2014, VII Samara Regional Intercollegiate Programming Contest
• 2014, Samara SAU ACM ICPC Quarterfinal Qualification Contest
• 2015, VIII Samara Regional Intercollegiate Programming Contest

Hi, Codeforces!

Educational Codeforces Round #1 will take place on 13 ноября 2015 года в 18:00 MSK for the first and second divisions. You can read about educational rounds here.

The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve five problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.

Educational rounds are (and would) be prepared by me, Edvard Davtyan from Saratov SU Daemons team. Problems was invented by me and MikeMirzayanov. Thanks to my teammate danilka.pro for testing problems and MikeMirzayanov for Codeforces, Polygon and idea of the educational rounds.

I hope you will enjoy the problems. If they will be too simple for you, you are welcome to the second educational round, problems there should be harder.

Good luck and have fun!

UPD: The first phase of round is over. I remind that the results is not final and you can hack any solution during the day.

UPD2: Please use only deterministic generators. For example you should not use srand(time(NULL)) with calling rand() function in C++. Your generator should always generate the same test.

Hi everybody!

First, I invite you to take part in an official Testing Round 12. The fact is, the Codeforces team has made numerous changes to the platform (details are below), and we want to be sure that the basic functionality remained unchanged. This round will have a shortened duration of 1.5 hours, consist of 3 (maybe 4) problems that you might have already seen before. Its purpose is to test the system on the one hand, and on the other hand — to brighten up a Wednesday evening. Of course, the round will be unrated.

Now the main thing. This coming Friday (yes, the 13th of November) Codeforces starts another line of rounds. We called them Educational Rounds. Using my students at the Saratov State University Programmings Competitions Training Center as an example, I regularly notice that even those who have a considerable progress in the results on the rounds often have narrow purview in terms of standard topics and ideas, they are not familiar with many well-known problems and methods. The fact is, the rounds often avoid any folk or classical subjects, thus underdeveloping the purview of young generation of the participants.

We are pleased to announce the start of a series of educational rounds! They will take place with the regularity of a round 2-4 times per month.

Their characteristics are like that:

• The duration is classic — 1.5 — 2.5 hours;
• The goal is rather to practice and to educate, than to compete;
• Not only problems, but also exercises can be used;
• Useful, even well-known ideas will be reused in order to introduce them to a wide range of participants;
• Often the formal text of the statements;
• Unrated (perhaps for now);
• We will try to conduct them in the ACM-ICPC mode (if there are long waiting lists, we may change the approach);
• The results that are obtained after the end of the round, are preliminary;
• After the end of the round will be a 24-hour period of open hacks — any visitor of Codeforces may try to hack any complete solution to a problem of the last round (either from a contest, or from practice), the source code of hacking solution is available (you can copy the text and, for example, stress it);
• All successful hacks from the previous item will be added to the official test set and after as long as 24 hours after the end of the round retesting of all complete solutions will be made;
• Only after the final standings based on improved test data, the results are final;
• The results of a round are calculated separately by division;
• Our ability to process such problems are limited, so actually the test suites from the jury are expected to end up incomplete — we are looking forward to your hacks!

Basically, we will be oriented towards the members of the second division, but often these rounds will be of interest to more experienced participants.

For now preparing problems to these rounds will be concentrated at the Saratov State University Programming Competitions Training Center, most of the work with the problems will be accomplished by Edvard Edvard Davtyan. We wish him good luck, enthusiasm and energy!

See you at the Testing Round 12, and later at the Educational Codeforces Round 1.

Good time of day, Codeforces!

I am glad to announce that this Sunday, 8th November at 19:30 MSK, Codeforces Round #330 for both divisions will take place.

The problemset of the round has been prepared for you with pleasure by Alex fcspartakm Frolov and me, Dan Sagunov. We want to thank the coordinator of Codeforces Gleb GlebsHP Evstropov for his valuable help in problem preparation, Mike MikeMirzayanov Mirzayanov for Codeforces and Polygon systems, Maria Delinur Belova for translating problem statements into English and Vladislav winger Isenbaev and Alex AlexFetisov Fetisov who have tested the round problemset.

Every participant will be given two hours to solve five problems. We have tried to make the round problemset variative and interesting and therefore we strongly recommend to read all the problem statements during the round. Scoring will be announced later as always.

We wish good luck and high rating to everyone!

UPD. We are sorry again for the mistake in Cdiv2/Adiv1 problem: jury's solution is working wrong in odd n case. We are hoping that other problems was (or will be such in upsolving) interesting and useful.

Anyway, let's congratulate the round winners:

First division winners:

1. jcvb
2. 2222
3. KAN

second division winners:

1. Tagrimar
2. fsps60312
3. uhateme

Editorial could be found here.

UPD. Problem Cdiv2/Adiv1 was fixed and now it has the statement and solution which jury meant it to be. Problem has been returned to the contest, so feel free to upsolve it.