Please subscribe to the official Codeforces channel in Telegram via the link: https://t.me/codeforces_official. ×

P___'s blog

By P___, history, 9 months ago, In English,

Hi,

Since nobody has mentioned this SRM, I do that here:

Time.

I am not the author, just want to increase the number of participants.

Thanks!

 
 
 
 
  • Vote: I like it  
  • +70
  • Vote: I do not like it  

»
9 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Can anyone tell me what can be done when the applet says "A connection to the server cannot be established" when I try to login? I tried autodetect, it doesn't work. It was working well a few weeks back.

»
9 months ago, # |
Rev. 2   Vote: I like it +11 Vote: I do not like it

Thank you so much for posting this! I always miss SRMs, and finally get to compete in one. GLHF everyone!

»
9 months ago, # |
  Vote: I like it +38 Vote: I do not like it

Does anyone have proved solution for 1000?

»
9 months ago, # |
  Vote: I like it 0 Vote: I do not like it

How to solve medium? (I have O(k3) with small constant which gets AC in 1.6s)

  • »
    »
    9 months ago, # ^ |
    Rev. 5   Vote: I like it +21 Vote: I do not like it

    upi is an expected sum of heights of nodes in tree with i nodes.

    dpi is an expected sum of length of paths in tree with i nodes.

    by linearity of expectation.

    Similary, because sum of length is sum of length in both subtrees and sum of length of paths going through root.

»
9 months ago, # |
  Vote: I like it +25 Vote: I do not like it

About Div1 Hard.

My solution was to look at only Pareto-optimal choices. First, we sort the friends by decreasing number of bits set. After that, we recursively pick or kick them in that order. The single important check which makes it run faster than like 2568 is as follows: if we kick a friend X, we also have to kick all further friends which have a subset of X's skills (otherwise, the choice wouldn't be Pareto-optimal).

In practice run, this takes <100ms on all the given tests. Can someone please either construct a test where this becomes slow, or prove a reasonable asymptotic bound for the number of Pareto-optimal choices?

  • »
    »
    9 months ago, # ^ |
    Rev. 3   Vote: I like it +13 Vote: I do not like it

    What about all (C(8, 4)) masks with 4 bits? Then it will be like 708?

    • »
      »
      »
      9 months ago, # ^ |
        Vote: I like it +10 Vote: I do not like it

      Challenge succeeded :) .

      A pity you were not in my room.

      • »
        »
        »
        »
        9 months ago, # ^ |
          Vote: I like it +16 Vote: I do not like it

        I wanted to challenge you with this exact test..

        However, I was so stupid that I did not know paste in TC is ctrl+v (while in macOS is it command + v). :P

  • »
    »
    9 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    On all vectors with 4 1-bits out of 8 it will be 708 / 8! ≈ 1010

»
9 months ago, # |
  Vote: I like it 0 Vote: I do not like it

can someone explain how to solve "div1 easy"? making second tree by removing edge from first tree.

»
9 months ago, # |
  Vote: I like it +1 Vote: I do not like it

how to solve div2b