Good day to everybody!

The next round for the participants of the second division will be held at September 22, 2015 at 19:30 MSK. Traditionally, the members of the first division may take part in the contest out of competition.

I (Vladislav Vishnevski) and igdor99(Igor Doroshev) are the authors of the round. We would like to please Zlobober (Maxim Akhmedov) for the assistance in the preparation of tasks, Delinur(Maria Belova) for translating statements into English, MikeMirzayanov(Mike Mirzayanov) for remarkable systems Codeforces and Polygon, as well as our friends daksenik(Dmitry Aksenik) and irevt(Ivan Revt) for their assistance in the round preparation. This is our first round, and, we hope, it won't be the last one!

You will be proposed 5 tasks and 2 hours for their solution.

The protagonist of the round is the parrot Kefa, who likes money and restaurants.

Good luck and high rating!

UPD: The scores — 750-1250-1500-2000-2500.

UPD: Editorial!

Hello, everyone! Codeforces Round #320 will be held at Sep/16/2015 18:00 MSK. Note that round starts in the unusual time!

The problems are from tmt514, Shik, drazil, and me(dreamoon_love_AA). Also we want to thank Zlobober for helping us preparing the round, AlexFetisov and winger for testing this round , Delinur for translating the statement into Russian, and MikeMirzayanov for Codeforces and Polygon.

This is my second time organizing a problemset for a Codeforces round (my previous round: #292). In my previous round all problems were provided by me. But I think that if problems are provided by more people, then the contest will be more interesting! So I asked my friends to help me this time. Hope everybody can have fun during the round!

Participants in each division will be given six tasks and two and a half hours for solving them (the last four problems in Div. 2 are as same as as the first four problems in Div. 1). Scoring system will be announced later closer to the start of the round.

Bayan is an Iranian software company working on large-scale web applications. It doesn't only develop the search engine, but also it holds an annual open competition Bayan Programming Contest with an on-site round in Tehran. The on-site round of 2015 became an international event with many strong participants.

Bayan has supported Codeforces on our Codeforces 5-year crowdfunding program. Thank you Bayan! This round is in your honor!

UPD 1: Due to technical reasons the round starts at 18:15 Moscow time.

UPD 2: The round will use the dynamic scoring with 250 points step.

UPD 3: Problems are ordered according to their supposed difficulty.

UPD 4: Winners!

Div1:

1) Um_nik

2) Egor

3) Endagorion

Div2:

1) EmaxxMaster

2) gongy

3) Irisviel_von_Einzber

UPD5: link of Editorial

Updated on 07/12 for the last time

• Postmortem -- explains a lot of stuff and it might help you decide if there's any point in watching this
• Twitch stream -- original livestream
• YT mirror -- because for some reason a lot of people wanted it

If you have any feedback (bad or good, doesn't matter as long as it's constructive), I'll be more than happy to hear it. Especially since I might do more of these (just not that long).

Updated on 27/11, because it got into "recent actions"

The stream will happen 28/11 Saturday 9:15 AM GMT+1 to 29/11 Sunday 10:15 AM GMT+1

The address for the stream is http://www.twitch.tv/fakepsyho — yes, I mailed with the support and coding on twitch is now perfectly fine. Also, the stream contains all of the essential information, so I'm not duplicating it here.

Also, I'm using this mic, so don't worry about sound quality ;)

Edits:

0) For people who are confused about who took my handle. This guy.

1) I thought I should make it a little bit more clear: I really want to hear what you would like to see. There are no stupid ideas. Want me to eat 0.5kg burger? Want me to play IWBTG? Want me to do push-ups (pls no)? It's entirely up to you what I will talk about. I'm giving free upvotes for every suggestion ;) My goal is to make it interesting for everyone (i.e. across all of the skill levels), so don't be afraid to suggest something that you may feel is very basic.

Short version:

• I will participate unofficially in M24, I don't want to break my streak of winning three 24h contests in a row ;)

• I will do the livestream with full commentary (and most probably with full code although it may not happen due to security risks)

• Since this is for you (across all the skill levels), I need to know what you'd like to see!

Longer version:

Since twitch was born, I thought about doing an educational livestream with solving some problems. The two biggest obstacles are: I wanted to do the livestream during the onsite contest (otherwise there's no thrill, and the conditions are artificial, so even educational values suffers). Unfortunately, this means that the contest would require the participants to have no internet connection. The other thing is that, doing the contest without commentary (and without interacting with chat) is quite boring. If I had participated, this would really hurt my performance. So, this really only works when I'm not 100% focused on winning. Unofficial participation in Marathon24 is a rare occasion to fulfill both of those requirements.

Current status:

• If you have any ideas for the setup let me know. I will stream the editor + any possible visualization (pretty much everything that happens on my main screen). I may stream the livecam if people want it for some reason. I'm guessing I will also use some virtual whiteboard for drawing/explaining things. I may set up secondary stream exclusively for visualization (so that people will know how the game looks even if I'm not looking at the visualization). I may set up dropbox so that all of my local files will be synchronized. The last thing may not happen due to security risk (some participating team could download it and it would be hard to detect).

• The stream will be full 24 hours. Probably even longer since I'll start a little earlier. I may also do some pre-finals testing stream, just to be sure to not mess up things during the finals.

• I'm considering using Twitch. I have some experience with using OBS since I started doing some lame speedrunning recently.

• Small disclaimer. I should also add that this is not 100% confirmed yet, but folks behind Marathon24 loved the idea (or they are convincing liars).

The things I can do:

• I want to start at the same time as other competitors will do. The first 15-30 minutes will be reserved time for me (and hopefully viewers too) to read the problem statement.

• For at least first few hours I will focus on the problem in the same way I would in the contest. I will definitely go way slower since I will be explaining all of the stuff I'm doing. I guess I will shift my priorities dynamically, depending on how I perform.

• I could try to do live interviews with some participants. That may be hard to do technically, but it's definitely a possibility. The problem is, people don't really like being hassled during the 24h contests.

• I'm not tied to talking only about M24. For example I could take a 2h break to talk about TC's marathons or stuff like that. It's entirely up to what you want to see.

• You will be able to ask me questions via chat (less reliable) or twitter (more reliable). I'll try to answer them, unless I will be already braindead ;)

So, to sum things up. Livestream. I need your ideas. Also, if you don't want to miss the news follow me on twitter. And don't worry. I don't spam there too much, since I haven't figured what's the point of it ;)

Hey there!

Today at 19.30, Moscow time there will be Codeforces Round #319 and it's strongly disadvised to skip it.

I'm the author of this round, my name is Dima Gorbunov and it's my first round on Codeforces. I really hope you're going to like it and everyone will find a satisfying problem. In order to increase the probability of finding that task, please read all of the problem statements.

As usual, I'd like to thank Zlobober for his invaluable help and his special sense of humour, sankear for coding additional solutions, Delinur for the English statements and MikeMirzayanov for amazing systems Codeforces and Polygon.

You're going to have two hours to solve 5 problems. Good luck!

UPD. The scores in first division are 500-1250-1250-2000-2750.

In second division — 500-1250-1500-2250-2250,

UPD2. Because of large size tests for some of the problems, system testing will be slow (it's possible that it will take several hours). Thanks for your patience!

UPD3. English editorial is also accessible.

UPD4. Winners!

Div1:

1). Marcin_smu

2). mnbvmar

3). I_love_Tanya_Romanova

Div2:

1). latisel

2). wrong_order

3). ntitry826

A special respect to al13n for correct solution of Div1.E during the contest!

Hi Codeforces!

As you already know from previous post, Bubble Cup is a programming competition organized by Microsoft Development Center Serbia for eight year in a row. And the finals is coming!

This year we came up with a wonderful idea to have an online mirror of the finals on Codeforces! We would like to thank MikeMirzayanov and Codeforces team for their work and support in making this happen.

The online competition will be held on 6th of September, Sunday 11-00 AM (Moscow time). The competition will last for five hours and it will run with the standard ACM ICPC rules. This will be a team contest on Codeforces, with teams consisting of up to three people. Amount of problems(7-10) will be anounced later.

Contest was mainly prepared by employees of MDCS (+ special thanks to knightL and Milanin for great help).

This contest will be unrated (mostly because rules of this contest and not usual for Codeforces (and it is first time we organize this kind of mirror).

10 best teams will receive our special T-shirts (each team member) +10 t-shirts will be handed out randomly to other participants of the top 100.

UPD please pay attention to that we updated maximal possible number of people in a team

Post with editorial, results and T-shirts will be posted a bit later

UPD Link to results and editorial post

Hello Codeforces,

In less than a two weeks, finals of 8th edition of Bubble Cup will be held in Belgrade, organized by Microsoft Development Center Serbia.

Unfortunately, there wont be Bubble Run contest this year (which was held last two years for university students in the same tame as BCup, and it was a 24h marathon style contest), but only ACM-style 5 hour long contest for both university and high school teams in the same category. You can read more about contest on the official website, and read tasks and solutions from past years in the booklets. (There are some very interesting tasks, especially from Run contests, so I encourge you all to take a look at them).

Usually, the contest was interesting only to teams from Serbia and it's region, but every year we can see more and more teams from other countries participating in qualifications, and now there will be teams from 7 different countries from Eastern Europe participating in the finals, which is the most I think. Certanly, it will be the toughest Bubble Cup ever, and that's the reason why I'm listing teams here. I hope there will be even more strong teams from other countries next year!

The new cool thing this year will be a BC conference where we will hear talks about competitive programming and maybe something more, from Psyho (Psyho), misof and MikeMirzayanov! (I can't wait for this! :D). Also, there will be a big party after the contest as MDCS celebrates 10 years anniversary.

For teams and guests who will come to the finals: Hope you will enjoy Belgrade and Serbia, and if you want to go to some fun places here, hang out, or maybe even spend few more days in this beautiful city, I'll be glad to help you :) If you have any questions, just post it in the comments, or send me a message. See you soon!

Teams (sorted by bonus penalty time):

Hello Codeforces community!

Codeforces Round #318 (for both divisions) will take place on August, 29 at 19:30 MSK. It is the Thanks-Round devoted to Russian Code Cup. You will be given 5 problems and 2 hours to solve them. Scoring will be announced close to the round. I strongly recommend you to read all problems.

RussianCodeCup is the largest open programming competiton for Russian-speaking participants by Mail.Ru Group. Its history started in 2011. And since the first championship RCC offers great problems and generous prizes. This year finals will be held on September, 19th. Wish good luck to all the finalists! Thank you, RussianCodeCup, for your gift on the 5th anniversary of Codeforces!

I am honoured to be a problem setter for this round. I wouldn't do it alone. I want to thank Zlobober for his great help with problems preparation and MikeMirzayanov (and all people working on Codeforces and Polygon) for this awesome site. It's an amazing place to learn and compete. My big thanks to winger and AlexFetisov for their help with testing a round. And to Delinur for translating statements. As you see, not only a setter creates a round.

It's my first Codeforces round but not my first problems here. You can check out A, C and D from VK Cup 2015 — Round 2. Also you might remember some of my problems in TC rounds. I'm very happy with finally preparing a full round for Codeforces and I hope you will enjoy it. I tried my best to prepare nice and diverse problemset, you will judge it. In all problems you will have to help Limak who is quite unusual bear.

I wish you great fun and no frustrating bugs. Looking forward to seeing you!

UPD: Scoring is 500-1000- 1750 -2000-2500 in div1 and 500-1000-1500-2000- 2750 in div2. Enjoy a round!

UPD: Editorial

UPD: Contest is over. The winners:

Div1:

1. Marcin_smu
2. mnbvmar
3. subscriber
4. LoneFox
5. Shef

Div2:

1. cescmentation_folch (5 problems solved!)
2. fhxb520630 (5 problems solved!)
3. bugCollector
4. Sehnsucht
5. okaduki1

And note from an author. There were some wrong solutions passing. Sorry for that. I tried my best to create strong tests but I failed a bit. Did you like this round? What do you think about problems?

Thanks for participating!

Hi, Codeforces!

Codeforces Round 317 will take place on August, 22 at 19:30 MSK.

The round is prepared by AimFund employees: Kostroma, riadwaw, yarrr, gchebanov, ArtDitel, SirShokoladina and zeliboba.

Scoring system will be static.

Thanks to Mike Mirzayanov(MikeMirzayanov) for brilliant platforms Polygon and Codeforces, problem coordinator Max Akhmedov (Zlobober) and Maria Belova (Delinur) for English translation.

Top 200 div1 participants will be awarded t-shirts. To learn more about AimFund please refer to our previous post.

This round is prepared as part of "5 years" Codeforces program as our present to community. This round is the first Thanks-Round devoted to companies donated significant money.

We wish you good luck and high frequency rating!

P.S: scoring 1 div 750-1250-1500-2000-2750. 2 div 500-1000-1750-2250-2500

P.P.S. Top-20 div2 participants will be awarded t-shirts.

Analysis

P.P.P.S. Dear friends. We are pleased to inform you that t shirts delivery will be under way next week. We hope you will really like them. Our sincere congrats again to you all!