By paladin8, 6 years ago, In English,

Hey everyone,

There are no CodeForces rounds coming up, so I thought I would set up a training round in the new Gym. The problems are from our local contest which I helped organize last October. We used it to select our team for the ACM-ICPC. There is a large range of problem difficulties, so I am sure everyone will have interesting problems to solve.

It will be held on Saturday, 1/28 at 8am Moscow time (4-hour contest) in the CodeForces Gym. I hope you enjoy the problems!

Update: The contest is over. Thanks for participating! If you didn't, please check out the problems anyway :) Feel free to discuss the problems in the comments below; I can outline solutions but I don't have a formal editorial.

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By MikeMirzayanov, 6 years ago, translation, In English,

Not so long ago in the English Wikipedia has been added to the article about Petr Mitrichev (Petr). Currently, there is a discussion of this article for removal due to the lack of significance. Here is a quote from the discussion: "I don't see how Petr is notable in Wikipedia standards. What makes him different from the hundreds or maybe even thousands of others who are on a similar level as him at competitive programming?".

By the way, there is the article about Reid Barton, the outstanding contestant from US. Who is more valuable for the history?

It would be nice if those who is familiar with the rules of Wikipedia, added to the discussion to support Petr.

By the way, the article actually seems incomplete and not disclosing the success of Peter. Maybe someone will undertake to improve?


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By witua, 6 years ago, translation, In English,


Tomorrow, January, 22-nd at 11:00 o'clock (Moscow timezone), will have place Codeforces Round #104! The problemsetter will be me, Herasymiv Vitaliy (witua). Thanks a lot to Artem Rakhov (RAD) for help in praparing the problems and Maria Belova (Delinur) for problems translation.

I hope you will like this round.

See you tomorrow!

Points destribution today is:

DIV1: 500-1000-1500-2500-2500

DIV2: 500-1000-1500-2000-2500

Thanks to all, and here are the results:

Division 1:

  1. tourist
  2. dzhulgakov
  3. kuniavski
  4. wuzhengkai
  5. shangjingbo
  6. ilyakor
  7. Gerald
Division 2:

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By Hohol, 6 years ago, translation, In English,

Hi there. I invite you to participate in my first contest. It will take place in Codeforces::Gym at 19:30 (Moscow timezone — UTC+4).

Problems are rather easy, so it will be more interesting for div2 participants.

Warning: now statements are only in russian. But later we will translate all our trains in english, so everybody will be able to run them in virtual contest mode.

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By MikeMirzayanov, 6 years ago, translation, In English,

Today we open a new project Codeforces::Gym, it will be started on January 19, 08:00AM. 30 minutes later, оn Thursday, January, 19, 2012 08:30 (UTC) the testing training contest will be started. The duration of the training is 3 hours. We invite you to join us! As all the trainings in Codeforces::Gym it will be held according ACM-ICPC rules.

As it will be a training, we will use problems from some programming contest (thank you, authors!). Please do not take part in the training, if you've seen these problems. Do not spoil training to other members. Thank you for your understanding.

Please use the official project tracker to report about bugs and feature requests.

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By Gerald, 6 years ago, translation, In English,

Good day, friends!

Today another Codeforces round for Div2 participants will be. As the last Div2 only round, this round has been prepared by a team of three people: NALPPolichka and Gerald. Traditionally, we express our gratitude for their help to Artem Rakhov (RAD) Maria Belova(Delinurand Mike Mirzayanov (MikeMirzayanov).

Score distribution: 500-1000-1500-2000-2500

Good luck and have fun of solving problems! :)

UPD: Problem analysis

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By MikeMirzayanov, 6 years ago, translation, In English,

We've made it! Or in any case, we are at least very close to it.

On January 19, 2012 at 12:00 we open a sub-project called "Gym". In short, its goal is to enable the Codeforces coders not only to participate in competitions and discuss them, but also to train and coach easily.

In fact, despite the wide diversity of online judges in the world, a well thought-out training service system does not exist. So, the expectations from this system are:

  1. Collection of online contests, composed mainly of the past official contests.
  2. Opportunity to integrate the final standings of past contests in the online contests to be able to train "against" the official participants.
  3. Opportunity to participate in the training at any time whatsoever, without fear that something breaks down and the server will fall. In short, reliability.
  4. Opportunity to write virtual contests and to solve the problems in a practice mode.
  5. Opportunity to participate both individually and as part of a team.
  6. Opportunity to keep the team while changing the team members.
  7. Opportunity to view various statistics and participation history, the possibility to compile and publish reports on selected participants/contest.
  8. Opportunity for a coach to add an online contest by him/herself, if this contest still does not exist. The process should be simple, reliable and maximally automated. The opportunity to parse the final standings of the past contests. The opportunity to add the attempts of the official participants to an online contest.
  9. Opportunity to view tests or other players' solutions for those who have solved the problem.
  10. Opportunity to find the training to one's taste, i.e. selecting by parameters.

The Codeforces Project:: The training aims to meet all these requirements. Already, nearly everything of the above list is available and whatever is not, will be available.

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By MikeMirzayanov, 6 years ago, translation, In English,

Hi everybody.

This change will not probably be among the most popular ones but nevertheless, vote counting rules and voting rules in general are going to change. Why? There are several reasons. The main is that we decided to give up the +2/-1 strategy that used to favor authors. This balance worked fine in the Coderofces's initial stage of development. However, it now leads to overrating many uninformative posts. Moreover, such rating is not valid. Thus, a positive vote and a negative vote now have the same value and the total rating sign now represents the actual attitude of the community members to the post or a comment.

Also, as Codeforces is a professional community of those who is interested in sports programming, it was decided to consider the participants' professional achievements. Thus, the value of a participant's vote now is delapnds on the participant's authority and the authority is determined by the rating. At this point I have to mention that the participant's authority is not influenced by his/her contribution. The votes' values do not differ dramatically: despite the fact that the red participants are 15+ times less that the blue ones, their votes' values differ less than their numbers.

We've introduced additional fraud detection heuristics (some of them had been used on Codeforces). These new strategies make it impossible to cheat in various ways or carry out a grudge, they make reverse engineering systems more complicated and influence some other stuff now and then. The exact details of the vote counting rules are not disclosed but the main principles are given above.

Of course, the change in vote counting will trigger considerable changes in some participants' contributions. I guess that's the indicator of the character of the votes' distribution and the voters' authority. All votes will be recounted that will lead to change in contribution.


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By goryinyich, 6 years ago, In English,

Hi there!

I'm the author of today's CF round.

During the round you'll again assist far away kingdom citizens in solving their everyday problems.

I want to thank Artem Rakhov for invaluable help during the round preparation, Maria Belova for translation of the problems, Mikhail Mirzayanov for excellent CF system and all participants for not leaving this event without your attention.

More AC verdicts and high rating to all of you! gl & hf

UPD: Round is finished. Congratulations to winners and awardees in both divisions!

3. Egor
6. Coder
8. neal

1. AcFast
2. songlj

UPD: Round editorial is published. Russian version will appear soon.

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By NALP, 6 years ago, translation, In English,

Dear friends!

The next competition - Codeforces Round 101 for participants Div2 will take place through a pair of hours, but the others can traditionally participate out of competition. It has been prepared by a small command of authors: me (NALP), Polina Bondarenko (Polichka) and Gerald Agapov (Gerald). There were Artem Rahov (RAD), Maria Belova (Delinur) and Michael Mirzayanov (MikeMirzayanov) with us as always.

It is a little bit about authors: all of us study at the Saratov State University at faculty of Computer Sciences and Information technology on 4th course. Now in free time from competitions and problems we pass the exams :) I’m a 1/3 part from command Saratov SU#2, and Gerald with Polina - 2/3 from Saratov SU#1. We would like our rounds became kind tradition on Codeforces and you have seen us among authors soon again.

We hope that this problems will be pleasant to all participants and everyone will take the deserved high place in the total table. Today you will help Santa Claus, Elf, Vasya and the other characters. All the similarities to real people are casual :)

The points on problems are distributed today in this way: 500-1000-2000-2000-2500

UPD: You can read the tutorial here.

UPD: Thanks all for participation! The round has turn out difficult enough and only one person among all participants (including Div. 1) has solved all offered problems - akim239. Our congratulations for him!!

UPD: our congratulations for Top-10 participants in competition:
3. frp
6. hex539
7. not
10. ggbuaa

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