Interleaved Strings

class Solution {
    public boolean isInterleave(String s1, String s2, String s3) {
        int n = s1.length();
        int m = s2.length();
        boolean[][] dp = new boolean[n + 1][m + 1];
        dp[n][m] = true;
        for (int i = n; i >= 0; i--) {
            for (int j = m; j >= 0; j--) {
                if (i < n && s1.charAt(i) == s3.charAt(i + j) && dp[i + 1][j])
                    dp[i][j] = true;
                else if (j < m && s2.charAt(j) == s3.charAt(i + j) && dp[i][j + 1])
                    dp[i][j] = true;
            }
        }
        
        return dp[0][0];
    }
}