Solution: Count the Number of Good Subsequences
Explore how to count good subsequences in a string by applying dynamic programming and binomial coefficient calculations. Understand how to use factorials, modular inverses, and frequency counting to compute the number of subsequences where each character appears equally. This lesson helps you develop efficient solutions and grasp core concepts like memoization and iteration for coding interviews.
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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 ...