Solution: Count the Number of Good Subsequences
Explore how to count the number of good subsequences in a string, where each character appears with equal frequency. Understand the use of dynamic programming and binomial coefficients to compute combinations efficiently, while managing large input sizes. This lesson guides you through calculating factorials and modular inverses to avoid recomputation, helping you solve this combinatorial problem within optimal time and space complexity.
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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 ...