LeetCode 115 Distinct Subsequences - Problem Statement

Solve Distinct Subsequences from LeetCode. Given strings $s$ and $t$, count distinct subsequences of $s$ that equal $t$. This is counting DP. $dp[i][j]$ = ways to form $t[0..j-1]$ from $s[0..i-1]$.

If characters match, you can use it or skip it. If they don't match, you must skip. For $s$ = 'rabbbit' and $t$ = 'rabbit', there are $3$ ways to choose which extra 'b' to drop.