Solution: Count the Number of Good Subsequences
Explore how to count good subsequences in a string where each character appears equally often. Understand the use of combinatorial calculations, factorial precomputation, and modular arithmetic with dynamic programming to efficiently solve this problem. Gain insight into handling character frequencies and applying the binomial coefficient in algorithm design.
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Statement
Count and return the number of good subsequences in the given string s. You may return the modulo
A subsequence is a sequence formed from another sequence by deleting some or no elements while keeping the order of the remaining elements unchanged.
A good subsequence is a subsequence of a string if it is not empty and the frequency of each character is the same.
Constraints:
s.lengthswill only contain ...