Solution: Count the Number of Good Subsequences
Explore how to count the number of good subsequences in a string by applying dynamic programming and mathematical combinations. This lesson guides you through calculating character frequencies, using factorials and modular inverses, and optimizing with binomial coefficients. Understand the algorithm and time-space complexity to effectively solve this class of coding interview problems.
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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 ...