Distinct Subsequences

1public int numDistinct(String s, String t) {
2    int m = s.length(), n = t.length();
3    int[][] dp = new int[m + 1][n + 1];
4
5    // Base case: empty t has one subsequence in any s
6    for (int i = 0; i <= m; i++) {
7        dp[i][0] = 1;
8    }
9
10    for (int i = 1; i <= m; i++) {
11        for (int j = 1; j <= n; j++) {
12            if (s.charAt(i - 1) == t.charAt(j - 1)) {
13                dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j];
14            } else {
15                dp[i][j] = dp[i - 1][j];
16            }
17        }
18    }
19
20    return dp[m][n];
21}