Solution: Count the Number of Good Subsequences
Explore how to count the number of good subsequences in a string by applying dynamic programming and combinatorial techniques. Understand factorials, modular inverses, and the use of binomial coefficients to efficiently calculate valid subsequences while excluding empty ones.
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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 ...