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/*

Author: Annie Kim, anniekim.pku@gmail.com

Date: Apr 6, 2013

Update: Jul 26, 2013

Problem: Path Sum

Difficulty: easy

Source: http://www.leetcode.com/onlinejudge

Notes:

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.

Solution: Recursion.

*/

/**

* 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) {

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);

}

}