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Solution: Distinct Subsequences

Explore how to use dynamic programming to count distinct subsequences of one string that equal another. This lesson guides you through implementing a space-efficient one-dimensional DP solution in C++, focusing on string indexing and recursive reasoning to optimize both time and memory usage.

Statement

Given two strings, s and t, determine how many distinct subsequences of s match t exactly.

Note: A subsequence is formed by deleting zero or more characters from s without changing the relative order of the remaining characters.

You may assume the result will always fit within a 3232-bit signed integer.

Constraints:

  • 11 \leq s.length, t.length 1000\leq 1000 ...