Interleaving String

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.
For example,
Given:
s1 = "aabcc",
s2 = "dbbca",
When s3 = "aadbbcbcac", return true.
When s3 = "aadbbbaccc", return false.
Solution:
1. public class Solution {
2. public boolean isInterleave(String s1, String s2, String s3) {
3. int n1 = s1.length(), n2 = s2.length(), n3 = s3.length();
4. 5. if (n1 + n2 != n3)
6. return false;
7. 8. boolean[][] dp = new boolean[n1 + 1][n2 + 1];
9. 10. dp[0][0] = true;
11. 12. // first row
13. for (int j = 1; j <= n2; j++) {
14. dp[0][j] = (s2.charAt(j - 1) == s3.charAt(j - 1)) && dp[0][j - 1];
15. }
16. 17. // first col
18. for (int i = 1; i <= n1; i++) {
19. dp[i][0] = (s1.charAt(i - 1) == s3.charAt(i - 1)) && dp[i - 1][0];
20. }
21. 22. // others
23. for (int i = 1; i <= n1; i++) {
24. for (int j = 1; j <= n2; j++) {
25. dp[i][j] = ((s1.charAt(i - 1) == s3.charAt(i + j - 1)) && dp[i - 1][j]) ||
26. ((s2.charAt(j - 1) == s3.charAt(i + j - 1)) && dp[i][j - 1]);
27. }
28. }
29. 30. return dp[n1][n2];
31. }
32. }