[leetcode]Path Sum

简单题。递归。

/**

 * Definition for binary tree

 * public class TreeNode {

 *     int val;

 *     TreeNode left;

 *     TreeNode right;

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

 * }

 */

public class Solution {

    public boolean hasPathSum(TreeNode root, int sum) {

        // Start typing your Java solution below

        // DO NOT write main() function

        if (root == null) {

            return false;

        }

        if (root.left == null && root.right == null) {

            return root.val == sum;

        }

        else {

            return hasPathSum(root.left, sum-root.val) || hasPathSum(root.right, sum-root.val);

        }

    }

}