Hello everyone!

Codeforces Round #167 will take place on Wednesday, February 13th at 19:30 MSK. This is my fourth Codeforces round and I hope not the last.

I'd like to thank Seyaua, sdya and Gerald for helping me to prepare the round. Special thanks to Delinur for translation of all problem statements into English.

Problems’ point values will be standard in both divisions.

I strongly recommend you to read ALL the problems.

Gl & hf ! :)

Contest is over. Congratulations to div1 winners:
1). tmt514
2). tourist
3). scott_wu
4). rng_58
5). dreamoon_love_AA

and div2 winners:
1). yefllower
2). Harlos
3). pseudopodia

You can view tutorial here.

Good day, friends)

Soon is coming regular Codeforces round #166 for Div.2 participants. Traditionally the others can take part out of the competition.

And again the problems were prepared by the group of authors: Pavel Kholkin (HolkinPV), Nikolay Kuznetsov (NALP), Rakhov Artem (RAD) and Gerald Agapov (Gerald). Traditionally thanks to Michael Mirzayanov (MikeMirzayanov) for Codeforces and Polygon systems and Mary Belova (Delinur) for translating the problems.

UPD: Score distribution will be not standard a little bit — 500, 1000, 1500, 2000, 3000.

We wish everyone good luck, successful hacks and high rating)

UPD2: the contest is over, we hope you enjoy it)

Congratulations to winners:

1) xrvpud221
2) xyz111
3) nanoha
4) wyx528
5) GuyUpLion

UPD3: the editorial is published, you can find it here

Bayan has published the schedule of the upcoming finals of their contest: http://en.bayancontest.ir/post/Contest-schedule

The contest should be quite compact: just two days and everything in the same hotel. All participants has to register themselves on Friday, February 15. Actually, the schedule does not say "February 15", it just says "Friday". Participants of the onsite event have got email invitations to Tehran for February 14-17, so let's assume we are talking about 15th of February, 2013. Speaking about dates, I have to mention that it's right now the year 1391 in Iranian Solar Hijri calendar. The New year is celebrated on March equinox, that's why the Sun is mentioned in the calendar name.

The contest will be held next day, on Saturday. All events should take place in the Parsian Azadi Hotel, which is located at the very north of the city next to Alborz mountains. Looks quite fascinating:

As far as I know, the Bayan Contest team has not communicated any transportation details to foreign participants. I checked out how you can get from the IKA airport to the hotel. One can take a bus to the subway station, cross the city in metro, exit near the Embassy of Russian Federation (Swiss Embassy is also nearby) and take a taxi. Here are the details: https://maps.google.com/maps/ms?msid=203576579397348428033.0004d54f4678ed65db970&msa=0 — please beware, this is not the official information, it's just my idea on getting around in Tehran.

UPD. All the participants will be welcomed and picked up at Imam Khomeini Airport by Bayan staffs, and will be transported to the hotel afterwards.

Hi everybody!

Have you spent the January as efficiently as we have? Here's a small list of innovations the users can see:

• Now not only the red coders can become coaches. The coders with a yellow handle are now accepted as well, provided that they have taken part in an official Codeforces round no earlier than 6 months ago and have taken part in at least 30 rated Codeforces contests. This innovation roughly doubles the number of potential coaches. So we invite you to check out your new role in the Gym!
• Now it’s absolutely easy to add a Polygon contest to the Trainings. All you need to do is to copy the data from contest.xml from the Polygon system contest interface to contest.xml in the sandbox folder in the Gym (use FTP).
• We’ve added protection against losing data in the Codeforces and Polygon projects’ forms. Now the textareas have a semitransparent ‘Drafts’ button in the upper right corner. You can use it to view or choose some previous versions of the text. The text is saving to drafts automatically. Now if the browser crashes unexpectedly or if you lose the session, that’s not a problem as you will be able to recover your text from the drafts.
• We’ve done some work on introducing the testing message shift from the system to the browser. You can see it on the Status page.The work hasn’t been completed yet and still has some issues, but on the whole it’s a functional system.
• We’ve updated the testlib to 0.8.7: we've boosted the performance of the ensure() function, the readStrictDouble stopped classify more-than-20-digit numbers as invalid, we’ve fixed some compilation warnings and fixed the compilation for some exotic cases.
• The Polygon system has better performance for problems with large manual tests.
• The contest and problem statements in the Polygon system now have reasonable URLs.
• We’ve fixed some bugs caused by cases in some old problems when the standard checker updates automatically, but testlib doesn’t. As a result, the checker cannot be used in such a problem, as it does not compile with the outdated testlib.h. Just in case, we’ve introduced the autoupdate feature for testlib, now updating it is going to be really easy.
• One more Polygon improvement. If a solution is marked as Main or Correct in the Polygon system, but it gets OK on a test in more than half of the time limit, then such situation gets highlighted in the invocations. Similarly, the system highlights the situation when a TL-solution gets TL, but it gets an OK in the double time limit.
• The problem descriptor in the Polygon system got attribute for the sample (example) tests. Now test element has attribute sample="true" value, if it is the test from the statement. This attribute is optional, it its absence is equivalent to sample="false".
• The compilers on judge servers have been updated to modern versions.

Hello everyone!

Codeforces round #165 will start today at 19:30 in Moscow time. It will be a round held in both divisions, the first one after a long two-week break for Div I participants. :)

This time the problems were prepared by me, Evgeny Vihrov (gen), and Krisjanis Prusis (cfk). Apart from competing together in ACM ICPC this year, we are also colleagues in a project that involves much algorithmic thinking. Actually, some of the contest problems were born during the work on this project.

In this contest you will get to know a legendary hero Emuskald of many talents and help him complete his ingenious ideas. The problems cover a multitude of algorithmic concepts, so as always we hope that each participant will find a problem that matches his taste.

Big thanks to Gerald Agapov (Gerald) for help during the preparation of this contest, to Maria Belova (Delinur) for problem statement translation and also to Mikhail Mirzayanov (MikeMirzayanov) for the excellent contest-making platform for Codeforces — Polygon.

We wish you an exciting round!

UPD1: Score distribution:

DivII: 500 1500 1500 2000 2500

DivI: 500 1000 1500 2000 2500

UPD2: Congratulations to the winners!

Div I

1. PavelKunyavskiy
2. Egor
3. tourist
4. rng_58
5. tomasz.kociumaka

Div II

1. woxihuanni
2. mnbvmar
3. QLSpirit_011
4. PraveenDhinwa
5. leviathan

UPD3: Tutorial is available.

Hello everyone!

The Codeforces Round #164 for Div.2 participants will start in several hours. Traditionally, the other participants can take part out of competition.

The hero of today's problems is Manao, which has been straining Georgian fellow programmers' minds for several years already. He made it to Codeforces pages thanks to Gerald and Delinur, who have assisted me in round preparation. The problems were also tested by Seyaua, sdya and Aksenov239.

The scoring system will be a little unusual: 500-1000-1500-2500-2500.

Good luck :)

UPD: The contest is over, congratulations to the winners:

1. first_love

2. dianbei_10

3. yefllower

4. dpij

5. cenbo

You can find the tutorial here.

Hello everybody)

Today is coming regular Codeforces round #163 for Div.2 participants. Traditionally the others can take part out of the competition.

The problems were prepared by authors: Rakhov Artem (RAD), Kudryashov Igor (Igor_Kudryashov), Pavel Kholkin (HolkinPV) and Gerald Agapov (Gerald). Traditionally thanks to Michael Mirzayanov (MikeMirzayanov) for Codeforces system and Mary Belova (Delinur) for translating the problems.

UPD: It is decided to use dynamic scoring system. The problems will be sorted from low difficulty to high by authors' opinion.

We wish everyone good luck and high rating)

UPD2: the contest is over, hope you enjoy it)

Congratulations to winners:

1) Aharon

2) marcoskwkm

3) ChaosLogic

4) Imsbuno

5) Conny

UPD3: the editorial can be found here)

Hello everyone,

I'd like to invite everyone to participate in a 5-hours Gym contest (both teams and individual participants can join) which will be held this Thursday, January 24th at 04:00 PM MSK (GMT+4), check for other time zones here: http://timeanddate.com/worldclock/fixedtime.html?day=24&month=1&year=2013&hour=16&min=0&sec=0&p1=166 (The registration will be opened 6 hours before the contest)

We will use the problems from the last ACM Arab Collegiate Programming Contest 2012 (English statements only), and the actual contest scoreboard will be merged into the Gym's scoreboard. Please don't participate if you already solved or read the problems. Hopefully the problems will be interesting for both Div1 and Div2 coders.

We encourage you to participate in teams to simulate the actual contest.

I'd like to mention that we used Polygon to prepare the problems for the actual contest, which is an amazing system and helped us a lot. Many thanks to Mike Mirzayanov and the whole team.

Edit 1: The registration is opened now, you can register here: http://codeforces.com/gyms

Thanks, Ahmed Aly

Hello!

I'm Squirrel Liss. I became the hero of today's contest. The writers of the contest are snuke, hogloid, DEGwer, and rng_58. I'd like to thank Gerald for helping preparation, Delinur for translation, and MikeMirzayanov for the Codeforces system. The point values will be standard: 500-1000-1500-2000-2500 for both divisions.

I will encounter many difficulties about stones, nuts, and sequences... Please help me!

Since 07:30 PM MSK is late here, the contest will be moved to 05:00 PM MSK. Please check the schedule in your time zone in timeanddate.com: http://timeanddate.com/worldclock/fixedtime.html?iso=20130120T22&p1=248&ah=2

UPD: Announced the detail of the contest.

The top five contestants in div1 were:

• 1: Petr
• 2: AleX
• 3: scott_wu
• 4: Zhukov_Dmitry
• 5: al13n

And in div2:

• 1: kesongyu
• 2: Moor
• 3: Qwaz
• 4: tsunayoshi
• 5: step5

Congratulations!

Also congratulations al13n and Komaki for solving div1 E problem.

The authors were

• D2 A: rng_58
• D2 B: snuke
• D1 A/D2 C: DEGwer
• D1 B/D2 D: DEGwer
• D1 C/D2 E: hogloid
• D1 D: rng_58
• D1 E: snuke

UPD: Tutorial was added here.

Hello everybody)

Today is coming regular Codeforces round #161 for Div.2 participants. Traditionally the others can take part out of the competition.

The problems were prepared by authors: Pavel Kholkin (HolkinPV), Nikolay Kuznetsov (NALP) and Gerald Agapov (Gerald). Traditionally thanks to Michael Mirzayanov (MikeMirzayanov) for Codeforces system and Mary Belova (Delinur) for translating the problems. Also thanks to Rakhov Artem (RAD) and Vitaly Aksenov (Aksenov239) for their help.

UPD: Today it is decided to use dynamic scoring system. But the problems will be sorted from low difficulty to high by authors' opinion!

We wish everyone good luck, successful hacks and high rating!

UPD2: the contest is over) hope you enoy it

Congratulations to winners:

1) poao900
2) persianpars
3) Sert
4) valentin.harsan10
5) MeinKraft

UPD3: the tutorial is published, you can find it here