Petr's blog

By Petr, 12 years ago, In English

I will be hosting Petr Mitrichev Contest 10 this Saturday (October 27) between 15:30 and 20:30 Moscow time (other timezones: http://timeanddate.com/worldclock/fixedtime.html?msg=Petr+Mitrichev+Contest+10&iso=20121027T1530&p1=166&ah=5 ).

The contest will be held at http://codeforces.me/gyms . Both teams and individual participants can join. The contest itself will be at http://codeforces.me/gym/100110 , but this link will be accessible only after the start of the contest.

There will be 10 problems of varying difficulty (most are quite difficult) for 5 hours. Your solution needs to be correct on all test cases to be accepted (the standard ACM ICPC rules). People will be ranked by the number of solved problems, and by total penalty time in case they're tied on solved problems, so don't be late! :) Note that in each problem you need to read the input from a file and write the output to another file — so don't read from stdin and don't write to stdout! Problem statements will be in English.

Feel free to ask any questions that you might have, and also please tell if there are any issues with the contest system — it's the first time I'm using codeforces.com/gyms .

Registration: http://codeforces.me/gymRegistration/100110

5 minutes before start, good luck everyone!

Solution ideas: http://petr-mitrichev.blogspot.com/2012/10/petr-mitrichev-contest-10-solution-ideas.html

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By Petr, 12 years ago, In English

There will be an online contest called Petr Mitrichev Contest 10. Problems are all mine, previously used in Petrozavodsk trainings for top Russian teams this September but not published elsewhere. The problems are not easy, but they are of different types and thus I hope everyone will find something interesting to solve. Both teams and individual participants can join.

I'm trying to choose the best time and place for the contest. My current proposition is: 15:30 to 20:30 Moscow time this Saturday, October 27 (in other timezones: http://timeanddate.com/worldclock/fixedtime.html?msg=Petr+Mitrichev+Contest+10&iso=20121027T1530&p1=166&ah=5 ). Looking at the contest list at http://clist.by/ and the new Yandex contest site not mentioned there (http://contest.yandex.ru/contest/ContestList.html ), all weekends are very busy, but it looks like IFMO trainings are not attended by many teams this fall and thus overlapping with it is OK.

I understand that the contest ending time in my proposition is 1:30AM in Japan and Korea and 0:30AM in China. People from Japan, Korea and China (and from Asia in general): is that too late? I'd host it earlier but there's a contest on acm.timus.ru that ends at 15:00 Moscow time that was very popular last year (http://acm.timus.ru/monitor.aspx?id=100 ), so I fear many contestants from Asia will take part there.

For the venue, I propose http://codeforces.me/gyms.

Please share your suggestions.

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By Petr, 12 years ago, In English
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By Petr, 12 years ago, In English
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By Petr, 12 years ago, In English

There's a live interview with me, tomek, Onufry Wojtaszczyk and Bartholomew Furrow in 25 minutes: https://plus.google.com/u/0/101571483150813305324/posts/DxaiBoikC8N

UPD. The interview is postponed, I'll write about new date and time :)

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By Petr, 13 years ago, In English

Before systest:

  1. tomek, problems 1 and 2.
  2. Petr, problems 1 and 2.
  3. Jacob, problem 3.
  4. romanandreev, problem 2.
  5. ACRush, problem 2.
  6. tomekkulczynski, problem 2.
  7. jakubr, problem 2.
  8. RAVEman, problem 2.
  9. Somebody, problem 3.
  10. gawry, problem 1.
  11. hos.lyric, problem 1.
  12. ilyakor, problem 2.
  13. iwiwi, problem 3.
  14. Po-Ru Loh, problem 1.
  15. vepifanov, problem 2.
  16. cerealguy, problem 1.
  17. pparys, problem 1.
  18. sdya, problem 1.

After systest:

  1. romanandreev, problem 2.
  2. tomek, problem 1.
  3. ACRush, problem 2.
  4. gawry, problem 1.
  5. hos.lyric, problem 1.
  6. Petr, problem 2.
  7. cerealguy, problem 1.
  8. pparys, problem 1.

Congrats romanandreev!

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By Petr, 13 years ago, translation, In English
Tags tco
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By Petr, 13 years ago, In English
As usual, I'll be doing live commentary on the World Finals on http://petr-mitrichev.blogspot.com/. Here are some pictures to get started.

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By Petr, 14 years ago, In English
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By Petr, 14 years ago, translation, In English
Here's a problem that has appeared at a recent contest: We are given a 7 times 7 field where some of the cells have numbers between 0 and 8, inclusive, and all remaining cells have dots. We want to find such allocation of exactly 10 stars to the cells with dots, at most one star per cell, so that each cell with a number has exactly that number of stars in its 8 adjacent cells. Moreover, we will only consider such 7 times 7 fields where such allocation of 10 stars exists and is unique.

Can you create a testcase for this problem that will kill backtracking solutions? It seems pretty hard to do at such small field, but it is possible!

Here are the official rules of this challenge: http://killbacktrack.appspot.com/rules.jsp.
And here's the website where you can test your testcases, which also keeps a scoreboard: http://killbacktrack.appspot.com/.

I've got a pretty good testcase, but I don't want to reveal it yet :) Please tell if there's some problem or possible improvement to the website.

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By Petr, 15 years ago, In English
You can find my impressions about beta round 2 in my blog: http://petr-mitrichev.blogspot.com/2010/02/codeforces.html

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