Solution: Count the Number of Good Subsequences
Explore how to count the number of good subsequences in a string by applying dynamic programming and binomial coefficient calculations. Understand how to use factorial precomputation and modular inverses to efficiently compute combinations. This lesson helps you grasp the solution strategy, optimize with memoization, and analyze time and space complexity to handle constraints effectively.
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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 ...