[leetcode] PathSum

package leetcode;

/**
* <pre>
* 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,
*               5
*              / \
*             4   8
*            /   / \
*           11  13  4
*          /  \      \
*         7    2      1
* return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
* </pre>
* */
public class PathSum {

    public class TreeNode {
        int      val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }
    }

    public class Solution {
        public boolean hasPathSum(TreeNode root, int sum) {
            if (root == null)
                return false;
            if (root.left == null && root.right == null)
                return root.val == sum;
            return hasPathSum(root.left, sum - root.val)
                    || hasPathSum(root.right, sum - root.val);
        }
    }
}