Variation of Atcoder Beginner Contest Problem — Make it Palindrome

Revision en1, by bihariforces, 2023-04-05 21:35:36

We have a variation of this, find sum of $$$F(x)$$$ for every subsequence of a string, and should be better than $$$O(N^2)$$$.

I can only think of $$$O(N^2)$$$ approach which involves finding individual contribution of every unequal pair of characters, can we optimize this?

Tags combinatorics, palindrome, optimization


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en1 English bihariforces 2023-04-05 21:35:36 384 Initial revision (published)