_115.java

package com.fishercoder.solutions;

public class _115 {
    public static class Solution1 {
        public int numDistinct(String s, String t) {
            int m = s.length();
            int n = t.length();
            int[][] dp = new int[m + 1][n + 1];

            char[] schar = s.toCharArray();
            char[] tchar = t.toCharArray();

            for (int i = 0; i <= m; i++) {
                dp[i][0] = 1;
            }

            for (int j = 1; j <= n; j++) {
                dp[0][j] = 0;
            }

            for (int i = 1; i <= m; i++) {
                for (int j = 1; j <= n; j++) {
                    if (schar[i - 1] == tchar[j - 1]) {
                        dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
                    } else {
                        dp[i][j] = dp[i - 1][j];
                    }
                }
            }
            return dp[m][n];
        }
    }
}