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Solution: Distinct Subsequences

Explore a dynamic programming method to determine the number of distinct subsequences in one string that match another string exactly. This lesson guides you through a space-optimized 1D DP solution implemented in C++, emphasizing the logic behind recursive dependencies and iteration order. By mastering this approach, you will understand how to efficiently solve subsequence matching problems with reduced memory usage and clear steps for implementation.

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 ...