Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
For example:
Given the below binary tree and sum = 22,
1. 5
2. / \
3. 4 8
4. / / \
5. 11 13 4
6. / \ \
7. 7 2 1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
Solution:
1. /*
2. * Definition for a binary tree node.
3. * public class TreeNode {
4. * int val;
5. * TreeNode left;
6. * TreeNode right;
7. * TreeNode(int x) { val = x; }
8. * }
9. /
10. public class Solution {
11. public boolean hasPathSum(TreeNode root, int sum) {
12. if (root == null)
13. return false;
14. 15. if (root.left == null && root.right == null && root.val == sum)
16. return true;
17. 18. return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
19. }
20. }