CSP2019 problem solution

According to the order of topics to write CSP

Gray code

The answer can recursively find difficult to find, then you can do every time.

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Brackets tree

Simple question, directly engage in a stack and then back to the tree.

Brackets tree nmsl

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Number of trees

Gugu Gu

Emiya family meal today

It is evident that this problem may be the inclusion-exclusion, then you can write a \ (O (mn ^ 3) \) The \ (dp \) .

Then consider that the two-dimensional state can make a difference later, this way it became optimization \ (O (2mn ^ 2) \) , then you can before.

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Divide

\ (\ texttt {__ int128} \) is not yet incense

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The center of gravity of the tree

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