ayush693's blog

How To approach this DP problem
By ayush693, history, 3 years ago, In English

I am not getting any idea how to approach this problem Please help https://codeforces.com/problemset/problem/234/C

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3 years ago, # |
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I used two-dimensional dp: dp[i][0] — if we continue negative sequence at index i dp[i][1] — if we continue positive sequence at index i

"state" is the number of changes needed to maintain a positive or negative sequence. Depending on the first element of the array we set base cases. Also, the last element of the sequence must be positive.

112223468

I prefer suffix-prefix sollution.

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    3 years ago, # ^ |
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    In fact, you don't even need dp. You need need to count the number of less than or equal to 0 and greater than or equal to 0s. The rest is unnecessary, and it's total possible without DP.

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      3 years ago, # ^ |
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      I also prefer this solution, but the author asked for dp approach.

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