Seyaua's blog

Codeforces Beta Round #85
By Seyaua, 13 years ago, In English
Hi to everybody from sunny Petrozavodsk!

Today me and my brother sdya prepared a few interesting problems for you. Because of very tight schedule in Petrozavodsk training camp, that includes rafting and watching anime all night long, we didn't have time to write long problem statements. So enjoy unambiguous short statements and you are welcome to invent some legends for them on your own.

Good luck and have fun!

Contest is over! Congratulations to winners!

Division 1:
  1. dolphinigle
  2. ilyakor
  3. marek.cygan
Division 2:
  1. wuzhengkai
  2. jayi
  3. superpear
Editorial.
  • Vote: I like it
  • 0
  • Vote: I do not like it

Comments Comments (81)
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13 years ago, # |
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thanks Seyaua &  sdya for preparing and creating problems.
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13 years ago, # |
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Sounds like a pretty awesome training camp.
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13 years ago, # |
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Just a little mistake "invent some legends for them on you own." Must be "invent some legends for them on your own."
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13 years ago, # |
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Seyaua & sdya, you guys look exactly the same in the pictures ;-)
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13 years ago, # |
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Thanks to problemset I hope enjoy the problems.
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13 years ago, # |
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which anime you guys finished recently ?
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13 years ago, # |
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Man I love these training camps you guys get to attend. I wish I could, but none happens in my part of the world. :( Hopefully some day I'll conduct one, when I am RED. ;)
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13 years ago, # |
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Is the judge dead?
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13 years ago, # |
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what happened with the judge?
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13 years ago, # |
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very slow testing
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13 years ago, # |
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How can I lock my solution?
The "lock" icon disappeared.
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13 years ago, # |
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I like statements :)
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13 years ago, # |
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unrate this round, please...
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  • 13 years ago, # ^ |
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    why? queue testing became normal after 20 min.
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    • 13 years ago, # ^ |
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      20 mins = 40+++ points,, if you know your solution is wrong after a very slow judging..
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  • 13 years ago, # ^ |
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    No, please, NO unrate!
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  • 13 years ago, # ^ |
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    That's a real awkward situation when you get to know that your solution was wrong after 20 minutes of submitting and you are coding the next problem.
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13 years ago, # |
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nice problems :)
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13 years ago, # |
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good short mathematical questions.
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13 years ago, # |
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I wanted to use custom test feature, but it was disabled. :(
Anyway, thanks for the good problems.
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13 years ago, # |
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In problem B i know the size 2n*2n but i didn't notice he give me the input 2n not n
i solved the problem as the input=n so i didn't divide by 2
so just n/2 ----> passed  :( :( :( :(

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13 years ago, # |
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I love these short and challengeable problems.
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13 years ago, # |
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Petya and divisors .... Nice problem  . But unfortunately i wasn't able to solve it. :(
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  • 13 years ago, # ^ |
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    Looks like I am not getting the statement right :-

    For the case 18 4.

    Why is 6 not a solution, it does not divide any of 14,15,16,17 . Or did I miss something miniscule.

    Thanks.
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    • 13 years ago, # ^ |
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      The 4 in "18 4" refers to the four lines above, 
      4 0
3 1
5 2
6 2


      18 has 6 divisors: 1,2,3,6,9,18, and only two of them do not divide 4,3,5,6.
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13 years ago, # |
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Can anybody tell me how testing is done when there are multiple solution for test case, like in todays div2 Problem C.
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  • 13 years ago, # ^ |
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    It checks to see if your solution satisfies the constraints...
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  • 13 years ago, # ^ |
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    Algorithm for checker.

    If solution prints anything and it is correct- AC (it is easy to check 2 conditions)
    If solution prints anything but not correct - WA
    If solution prints -1, and jury prints -1 AC
    If solution prints -1, but jury have answer WA
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  • 13 years ago, # ^ |
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    Testing procedure is not always exactly full comparing of your answer and jury answer.
    Usually authors write special program - checker, that checks your answer, using input and jury output for this test. Moreover, sometimes checker program can be much more difficult then solution.
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13 years ago, # |
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I made a funny mistake, failed my C because I thought that 1<<6 is less than 40 :-)
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13 years ago, # |
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In division 2, C; test 50 looks like that: 2 1 1 and the supposed answer is 0 1. However, in problem it is said that all the numbers should be positive integers, it means 1 or greater. So with n=2, it is impossible to satisfy y=1. My answer was -1 then, but i got WA.
Did I miss something or it is a mistake in author's solution?
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  • 13 years ago, # ^ |
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    No, your answer is 0 1, and the correct one is -1. At least, that's what I see below your solution.
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    • 13 years ago, # ^ |
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      Ah damn, it always confuses me... Sorry for my useless post.
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  • 13 years ago, # ^ |
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    Your answer is not "-1" but "0 1".
    You can see checker message in test protocol.

    In test 50 for your solution message is: "wrong output format All numbers must be positive, but the 1-th isn't (1-based)."
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13 years ago, # |
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Excellent contest like it (though my rating went down)
Can anyone help me with the problem Div1C.....
How the answer for input 4 4 is 12............... 
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  • 13 years ago, # ^ |
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    OXOO
    OOOX
    XOOO
    OOXO

    X - spots, where all the spiders ends up, you can reach an X from any square.
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  • 13 years ago, # ^ |
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    finally spiders at :
     (1,3)
    (2,1)
    (3,4)
    (4,2)

    (numbering starts from1 )
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13 years ago, # |
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This is the first time in my life I've become Blue.

Nice Problem-set.
but I don't know why the judge queue took so much time.

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13 years ago, # |
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I think brief description is cool. With possibly as much mathematical expressions as possible to reduce ambiguity.
Thanks  Seyaua and sdya for problems :)
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  • 13 years ago, # ^ |
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    ya bro...i loved the problem c...nice greedy...and look at the input set man....!!! when you go to check (Y-n+1)^2 here there remains input like 100 1 1... really cool...rare experience\m/
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13 years ago, # |
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Nice short-statements problem set!
Any one else didn't see the n.m<=40 constraint in C DIV-1?
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  • 13 years ago, # ^ |
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    Many didn't see (at least three other persons except me), that's why I personally don't like the round.

    UPD: Yeah, baby, give me more minuses, people never like truth =)
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    • 13 years ago, # ^ |
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      It could have been more clear this way (same meaning):
      The first line contains two space-separated positive non-zero integers n and m (1 ≤ n·m ≤ 40) — the board sizes.
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  • 13 years ago, # ^ |
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    It takes me about 45 minutes to find a solution for 1600 cells and after beind disappointed, I read the problem once again and saw that it is n.m<=40 not n,m<=40
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    • 13 years ago, # ^ |
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      Ohhhhh and I just realized!! I can't believe myself.

      n x m  would have been a lot clearer
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13 years ago, # |
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Finally Petr owns both TC and CF.
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13 years ago, # |
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Is there any way to see on which test case my solution was hacked i.e. the hacker's input during the contest?
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13 years ago, # |
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Can someone please explain the solution of problem E from Div 2? :D
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  • 13 years ago, # ^ |
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    It is basically brute-force but reducing complexity to solvable limits by using memoization/bottom-up DP.
    1.first rotate the grid such that smaller side remains at top, which is of length <= 6. (sqrt(40)).
    2.then try all possible subsets (2^6).
    3.any particular state is given by settled spiders in curr. row and prev row. and the curr row number.
    4.Easy if you have solved similar problems previously.
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13 years ago, # |
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it isn't fair!
the timer should be started as a problem is opened or at least when someone enters the contest area!
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  • 13 years ago, # ^ |
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    But your first submission was only after 34 minutes, when judge has already begun to work properly
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  • 13 years ago, # ^ |
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    I think this is a fair complaint.
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  • 13 years ago, # ^ |
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    As I understood this complain is not related to today's incident, but for CodeForces format as well. But it's the rules - the timer starts at the set time.
    But seriously, I don't get what isn't fair - that's the rules of this competition. It's like arriving late to a rock star concert and complaining afterwards that he started before you arrive. The advantages and disadvantages of particular format (CodeForces/ACM/TopCoder/IOI etc.) is another topic.
    Sorry if I misunderstood your post.
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13 years ago, # |
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yes, but I entered the room 26 minutes after the beginning and it should be 8 nor 34!
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  • 13 years ago, # ^ |
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    Why? This is not TopCoder.
    Here time is calculated like ICPC style, from the beginning of the contest. You can read about this rules in FAQ.
    And anyway, you've missed the time when judge had troubles.
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13 years ago, # |
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Hi! This was a great round, except for some technical issues that we all noticed, but oh well, they didn't really affect anyone's score in my opinion :D When is the editorial going to be available?
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13 years ago, # |
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Editorial eagerly awaited !!
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13 years ago, # |
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The next context is coming soon.But the editorial still isn't available!
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  • 13 years ago, # ^ |
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    Not only the contest (#86), its editorial too!
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13 years ago, # |
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What an elongated "soon" you mentioned. The tutorial isn't available yet! :O
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6 years ago, # |
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?detaR tI sI

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