Solution: Count the Number of Good Subsequences
Understand how to count the number of good subsequences in a given string by applying dynamic programming techniques, factorial computations, and modular inverses. This lesson guides you through calculating combinations efficiently to solve this common coding interview problem. You will learn to implement the solution step-by-step, analyze its time and space complexity, and reinforce your grasp of optimization strategies for algorithmic challenges.
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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 ...