Solution: Count the Number of Good Subsequences
Explore how to calculate the number of good subsequences in a string by applying dynamic programming and binomial coefficients. Understand how to use factorials and modular inverses to optimize calculations and exclude invalid empty subsequences. This lesson helps you implement an efficient algorithm while analyzing the 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 ...