Path Sum

 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class  {
    public boolean hasPathSum(TreeNode root, int sum) {
        if (root == null) return false;
        if (root.left == null && root.right == null) 
            return sum == root.val;
        return hasPathSum(root.left, sum-root.val) || hasPathSum(root.right,sum-root.val);
    }
}