With the help of some experienced and respected members of the community (thanks!) there was formulated a rule that allows a third party code to be used under certain conditions. Please read carefully the text.

The following text will go as part of a renewed competition rules. The closest contest will be held already on the updated rules. Thus, there are about two days for further details, if something is unclear.

Solutions and test generators can only use source code completely written by you, with the following two exceptions:

1. the code was written and published/distributed before the start of the round,
2. the code is generated using tools that were written and published/distributed before the start of the round.

Any usage of third-party code should not violate the right holder’s license or copyright. Remember that published code is not always free to use! At the request of the right holder, any code that violates the license or copyright may be considered as violating the rules.

All the changes in the code from exceptions 1) and/or 2) must be made solely by you.

If there are any doubts about the time of publication, possible collaboration etc., a participant will have to prove his/her complete innocence by presenting compelling and satisfactory evidence.

Currently, the only reliable proof is the presence of code on the Internet and the presence of the used edition in the cache of well-known search engines.

For example, this rule accepts the use of the code from the website http://e-maxx.ru/ if the code was written and published/distributed before the start of the round. With the help of search engine caches, it can be easily shown that such code doesn't violate the rules. Similarly, it is permissible to use the code from a book/article that was published before the contest. On the other hand, using team reference code (for example, prepared for ACM-ICPC World Finals) is not allowed if there is no reliable and objective way to prove that the code was written before the contest.

This rule doesn't loosen the rules about prohibiting of communication, discussion, or any other form of communication between the contestants on any topics about the problems during the round.

Hello everyone!

We invite you to participate at Codeforces Round #198, scheduled Friday, 30 August at 7:30 PM MSK. The authors of the problems are me and Linh (ll931110). We are also the authors of the Codeforces Round 191 (Div. 2). Last time, we received positive feedback for the round. We hope this round will be at least as good as the previous one.

Linh brought to you D2-C/D1-A and D2-E/D1-C. I wrote the rest of the tasks. We hope you'll spend more time writing on the paper and thinking than typing on the PC. In addition, all tasks don't require too complicated algorithms. Instead, all require some creativity, hard working and patience. BTWs, the main character of the round will be Iahub, as in the previous one.

I'd like to thank to DamianS, Gerald and Aksenov239 for testing the round. Without them, my job would have been certainly harder. Also, thanks to Delinur for translating the tasks and to MikeMirzayanov for the amazing Codeforces platform and Polygon system.

We wish everyone high rating and to have fun!

UPD1 The score distribution will be dynamic in both divisions. For more information please look here. The problems are sorted in our expected order of difficulty.

UPD2 Thanks for everyone who participated. I hope you fount problems interesting. Also, I think my prevision that you'll think more than write was correct :)

Congratulations to the winners.

Division 1

1. yeputons
2. KADR
3. ftiasch
4. Myth5
5. huzecong
6. R_R_
7. Gabaum
8. James
9. ifsmirnov
10. niyaznigmatul

Special congratulations to Igor_Kudryashov, the only person who solved D1-E!

Division 2

1. Azat_Yusupov
2. angel_of_monkey
3. molamola.
4. iseriohn
5. Mato_No1
6. silver__bullet
7. TheDude
8. Nero
9. khuebeo
10. uc-nuts

UPD3 The editorial has been finished. I'm waiting for your feedback / questions.

Hello, Codeforces.

Today at 19:30 moscow time, Codeforces Round #197 will take place.

Authors of this round are me and Gerald. I'd like to thank the following people for their contribution: Delinur for translation of the statements and MikeMirzayanov for creation and supportion of Codeforces.

The score for problems: 500 — 1000 — 1500 — 2000 — 3000.

Good luck!

UPD: To make the announcement more interestiong and thrilling we decided to add a horse joke and a photo, taken during the preparation of the round.

Q: What did the teacher say when the horse walked into the class?
A: Why the long face?

337A - Puzzles

First, let's sort the numbers f[i] in ascending order. Now assume that the smallest jigsaw puzzle which the teacher purchases consists of f[k] pieces. Obviously, she should buy the smallest n puzzles which are of size f[k] or greater to minimize the difference. These are the puzzles f[k], f[k+1], ..., f[k+n-1] (this is not correct when f[i] are not distinct and f[k]=f[k-1], but such cases can be skipped). The difference between the greatest and the least size of the puzzles in such set is f[k+n-1]-f[k].

To choose the optimal f[k], we can test every k between 1 and m-n and pick the one producing the least difference. The full algorithm is as follows:

read(n, m, f[1..m])
sort(f[1..m])
best = INFINITY
for k = 1 to m-n
  best = min(best, f[k+n-1] - f[k])
print best

Hello everyone!

Codeforces Round #196 will begin in several hours (August 16, 20:00MSK).

You will mostly have to deal with Manao's problems, which this time range from watching movies and taking quizzes to treebuilding and battling evil undead.

I'd like to thank the following people for their contribution to this round's preparation: the Codeforces problem coordinator Gerald; Seyaua, who tested the problems; Delinur, who translated the problem statements into English; and Aksenov239, who proof-read the statements.

The points distribution in both divisons will be standard.

By the way, Sammarize mentioned he was probably the eldest author of a Codeforces round in the Russian version of his latest round's announcement. Since I'm even older, now I am holding the title ;)

The contest is over, I really hope that enjoyed it. The standings: Div1, Div2. Congratulations to top performers in Div1:

1. tourist
2. ilyakor
3. al13n
4. aa2985759
5. rng_58

Congratulations to the winner of Div2, Ruthles, too!

The problem analysis is here.

Hello!

Soon (on August 9 at 19:30 MSK) you are lucky to participate in Codeforces Round #195 for Div. 2 participants. Traditionally, Div. 1 participants can take part out of the competition.

Problems have been prepared by me. I want to thank Gerald Agapov (Gerald) for help in preparation of this round, Eugene Sobolev (Seyaua), Vitaly Aksenov (Aksenov239) and Sergey Sukhov (Serega) for testing of problems, Alexander Ignatyev (aiMR) for testing of problems and for translation of tutorial, Michael Mirzayanov (MikeMirzayanov) for marvelous Codeforces and Polygon systems, Mary Belova (Delinur) for translation of statements.

We wish everyone good luck and high rating!

UPD: English tutorial

UPD: Congratulations for winners:

1. Triolossus_3
2. WHITE2302
3. PM2.5

Separately, I want to congratulate Egor Kulikov (Egor) — the only person who had passed the all problems!

Hello everyone!

The second round of MemSQL start[c]up will take place on August, 3rd, 10:00am PDT. There will be two contests running simultaneously, one for people who participate onsite, and one for everybody else who advanced to the round two. Both rounds share the problemset and are rated based on the combined scoreboard.

Onsite participants will have special prizes for first three places. All onsite participants as well as the top 100 in the online contest will receive a start[c]up t-shirt.

People who have not advanced to the round two can participate in the round unofficially. Unofficial participation will be rated.

The contest will be 3 hours long, and will feature 6 problems. The score distribution is 500-1000-1000-2000-2500-3000.

The problem set has been developed by MemSQL engineers pieguy, nika, exod40, SkidanovAlex and dolphinigle.

Good luck and happy coding!

UPDATE: Editorial is up!

Hi everyone!

For three years ABBYY Cup finalists have been meeting for ABBYY Open Day at the ABBYY Moscow office (Headquarters) in summer. This year hasn’t been an exception. As an organizer I will tell you about ABBYY Open Day 2013 which took place on July 17th.

It should be noted that it was rainy all the days before the contest day. We were very concerned: we have announced the entertainment which was strongly depending on the weather. Evidently the Universe wanted to see the outdoor part of the Open Day and decided not to spoil the weather by rain. The day began with breakfast and watching a funny video with a promising name “The truth about ABBYY”.

At 10:40 AM the contest started. For me as an organizer this is nice time. There is silence in the room, participants solve problems, I can relax for a moment watching the results and rooting for my favorites. In two hours we got the final standings. In particular, I want to congratulate with great results Mimino, who was the only non-speaking Russian participant. Every ABBYY Open Day cannot take place without the talk about the company. So, after dinner the participants met the CEO of ABBYY Sergey Andreev. Then our technical consultant for Compreno products Alexander Kostuchenko demonstrated achievements of ABBYY R&D in computer linguistics.

We’ve had a tour on the office where the participants managed to see how the working process of programmers is organized. At the end of the official part we’ve had the most pleasant event, the awarding. This year all the winners could get the gift from Smart Beaver himself, the main character of all ABBYY Cup problems. Next the unofficial part of the day began. It was the quest in the centre of Moscow. All the participants divided in teams, got the rules and the tasks and scattered throughout Moscow. In order to find the finish line the teams should have answered all the questions about Moscow sights or they could drop the quest at any time by calling us. However, nobody wanted to give up. Imagine how hard these tasks were for Mimino. We translated the rules especially for him and provided a translator to his team.

At 10 PM the teams started to gather at the finish in one of the Moscow’s anticafe. We have been waiting for them with pizza, salads and Smart Beaver! Our ABBYY Open Day has ended. We are very happy that there are participants who visit us every year. And this year we have had one international participant. It was nice to meet everyone. See you next year!

https://get.google.com/albumarchive/pwa/114842746780416406882/JInSLJ?authkey=Gv1sRgCLPuzoHEm4X_YQ

Good day for all!

I invite you to participiate in the round 194. I'm author of it. It is my fourth round, but three previous ones were a long time ago: Codeforces Beta Round 79 (Div. 1 Only), Codeforces Beta Round 94 (Div. 1 Only), Codeforces Round 110 (Div. 1) (I apologize to the div-2 participants that I have mention only div-1 round, but even one link looks bulky).

This time you will help to boy Gerald cope with his problems as in the Codeforces Beta Round 79 (Div. 1 Only). This time his problems are so serious that he became coordinator of contests on the Codeforces, to be able to throw his problems to you.

I want to thank Gerald for he is great as coordinator. When you are work with him you are fill the everythink is under control. Moreover I want to thank Maria Belova for translation problems statements to the English.

This round will be held in unusual time — 12:30 Moscow Time.

Score distribution is standart: 500 — 1000 — 1500 — 2000 — 2500.

Thanks everyone for participation, welcom to editoral.

Congratulations to winners:
Division 1:
1. KADR
2. RAVEman
3. PavelKunyavskiy
4. Dmitry_Egorov
5. RAD
6. sy2006
7. mmaxio
8. riadwaw
9. niyaznigmatul
10. RomaWhite

Separate note two Ukrainian participiants, who only solve all five problems!

Division 2:
1. IMOiguanas
2. savsmail
3. suyash666
4. AntiForest
5. kang205
6. jschnei
7. littlepanda
8. langdamao
9. 9mmlitswe
10. Renkai

Rah-rah!

We are moving forward to accelerate testing. In fact, when our rounds attract 3500+ registrations, it is hard to test all the submissions on nine computers "Core 2 Duo E6750, 2.66 Ghz, 3Gb".

Computer Science Department of Saratov State U has recently got 20 new computers i5-3470, 8Gb. After a little research it was found that if boost CPU to 3.5Ghz (of course, turning off all sorts of turbo boost and after many hours of stability check), the speed is approximately equal to twice the speed of the old testing machines. This is very convenient as it will in future only to divide all the time constraints in the problems by 2.

We have moved to testing on new computers and we do it in compatibility mode. This means that all the time constraints before the start of the program are divided into 2, the program is executed, and at the end a running time is multiplied by 2. In fact, if you do not use the cut-off by time or some other unsavory stunts, you will not detect any changes.

Old testing machines are switched off now.

To be very precise, the new computers are not so fast as 2x old. That is in compatibility mode it is normal to notice a slight degradation in speed.