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tzc___wk's blog

By tzc___wk, history, 2 months ago, In English,

You're given $$$n$$$ integers $$$a_1,a_2,\dots,a_n$$$, you need to count the number of ways to choose some of them (no duplicate) to make the sum equal to $$$S$$$. Print the answer in modulo $$$10^9+7$$$. How to solve this problem in polynomial time?

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By tzc___wk, history, 4 months ago, In English,

I'm recently thinking of a problem. Given a sequence $$$a$$$, find the value of $$$\sum_{l=1}^n \sum_{r=l+1}^n lis(a[l...r])$$$. Where $$$lis(a)=$$$ the longest non-decreasing sequence of $$$a$$$ and $$$n$$$ is the length of $$$a$$$. $$$n$$$ is large to $$$10^5$$$ and $$$a_i$$$ is extremely small, only $$$20$$$? I can't think of a solution. Can anyone help me? Please.

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By tzc___wk, history, 5 months ago, In English,

Is it a bug or it is done intentially? Two contests with similar title make me feel nervous.

MikeMirzayanov Vovuh please give a response after reading this blog.

UPD: the contest name has already been undated.

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