MciprianM's blog

By MciprianM, 15 years ago, In English
Today I participated in the first rated event on the codeforces site.

I got blue and I was promoted a lieutenant.  All I did was solve three problems(A, B and C). I could have solved four, but I misinterpreted problem D's statement. I thought it asks us to find the minimal number of increasing subsequences and I don't know how to find that(yet).By the way if you know how to solve it leave a comment. As an example the answer for 1 2 10 4 5 11 9 is 2, that is 1 2 4 5 9 and 10 11.

I'm still struggling to find a O(n2) algo for the probability problem E. I saw that many had O(2n) DP so I will try to check that out too. I'm not too good at probabilities so it will take me a while until I will crack it.

I can't wait for round 17!!!
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15 years ago, # |
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Well, you have overestimated problem D. All you need - "dumb" simulating of walking through log file, keeping in your memory time of the last message and total count of messages appeared at this time in a row (we need to do this for the case, when more than 10 messages appearing on the same hour and minute -> so they can't be assigned to one day).

For your case "1 2 10 4 5 11 9" answer will be 3, we've got (1 2 10), (4 5 11) and (9).

For problem E DP is really good, especially if we don't get WA on double precision =)

  • 15 years ago, # ^ |
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    I have thought more on problem E and I now think that an O(n2) algorithm might not exist on problem E. I told you I'm not that good at probabilities.