Solution: Count the Number of Good Subsequences
Explore how to count the number of good subsequences in a string by applying dynamic programming and combinatorial techniques. Understand how to efficiently compute factorials and modular inverses to solve this binomial coefficient problem, and learn to exclude the empty subsequence for accurate results. This lesson builds your skill in applying optimization strategies to algorithmic challenges like counting character-based subsequences, helping you tackle similar coding interview questions with confidence.
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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 ...