Solution: Count the Number of Good Subsequences
Explore how to count the number of good subsequences in a string by applying dynamic programming techniques. Understand character frequency calculations, binomial coefficients, and the use of factorials with modular inverses to optimize computations. This lesson guides you through implementing an efficient algorithm with a clear explanation of time and space complexities.
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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 ...