### HolkinPV's blog

By HolkinPV, 9 years ago, translation,

Welcome dear friends)

We are glad to introduce you regular Codeforces round #113 for Div.2 participants. Everyone can traditionally participate in it.

Problems are prepared by known command of authors: Kholkin Pavel (HolkinPV), Nikolay Kuznetsov (NALP), Artem Rakhov (RAD). Also thanks to Gerald Agapov (Gerald) for his help, Michael Mirzayanov (MikeMirzayanov) for Codeforces system and Mary Belova (Delinur) for translating problems.

In todays contest would be one innovation. Score distribution would be dynamic. More information you can find here)

We hope that todays round would be succesful. We wish you good luck and high rating!

UPD: The contest is over. Hope you enjoy the problems) the editorial is already here)

Congratulations to winners:

• +71

 » 9 years ago, # |   +2 My friend tried to register and got the message "Cannot register user now. Try later or contact the administration.". Why?
•  » » 9 years ago, # ^ |   -9 And I have registered twice.
•  » » 9 years ago, # ^ |   0 help him~~~~~~
 » 9 years ago, # |   0 That wasn't a good idea . At least If you told before I think that would be better . But thank you for your great idea . Hope best for everyone .
 » 9 years ago, # |   0 Can anyone give some hint(s) for problem D? :D
•  » » 9 years ago, # ^ |   -8 A typical DP problem, but you must record the pair during the dp loop.
 » 9 years ago, # |   0 If after the test completed, the number of contestant who can solved the problem change, will it change the problem's score?
•  » » 9 years ago, # ^ |   0 Yes, the problems' score can change after system testing.
 » 9 years ago, # |   0 On the Contest page, both of 114 CF contest are for DIV 1 ?
 » 9 years ago, # |   +6 I was wondering what point distribution the author had thought for the problem set ?
 » 9 years ago, # |   +1 Any tutorials coming?
•  » » 9 years ago, # ^ |   +1 There is Russian one
 » 9 years ago, # |   +3 Please publish the editorial in English, is the second consecutive round that comes only in Russian. If not possible, some better than the google translator.
•  » » 9 years ago, # ^ |   0
 » 9 years ago, # |   -8 Please provide the Editorial in English..otherwise wont get any benefit by mere participation !!
•  » » 9 years ago, # ^ |   0 It's already published. http://codeforces.ru/blog/entry/4173?locale=en
•  » » » 9 years ago, # ^ |   -11 Thanks !! Please explain the approach to Problem E ie Tetrahedron.
•  » » » » 9 years ago, # ^ | ← Rev. 2 →   +1 Okay, the solution is DP. Let's number the vertices A, B, C, D from 0 to 3 instead, and let dp[i] mean how many cyclic paths currently begin and end at i. At first, we only have dp[3] = 1 and dp[0] = dp[1] = dp[2] = 0, and we only are considering paths of length 1. Now, to calculate how many cyclic paths of length n there are, you iterate n times, updating the DP table in the following manner (pseudocode): http://pastebin.com/XyNsyMk6
•  » » » » » 9 years ago, # ^ |   0 Thanks for the great explanation :)
 » 9 years ago, # |   +1 help!help!I got a WA on test #12,my code is [submission:1403496]，the former 11 tests are all passed, Who can help me find out the problem of my code?
•  » » 9 years ago, # ^ |   0 You shouldn't /4 because 3^n is modular (try *(1000000008/4))
•  » » » 9 years ago, # ^ |   +1 Thank you for your help! :)
•  » » 9 years ago, # ^ |   0 In order to divide on 4 by modulo of 1e9+7 you need to multiply by its inverse (found with extended gcd or basing on Fermat's theorem).
•  » » » 9 years ago, # ^ |   +1 :)thanks a lot!