Leetcode--Path Sum

Problem Description:

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.
分析：利用递归的思想，一旦出现结果就返回。
代码如下：

/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
bool hasPathSum(TreeNode *root, int sum) {
bool left=false,right=false;
if(!root) return false;
if(!root->left&&!root->right&&root->val==sum)
return true;
else
{
left=hasPathSum(root->left,sum-root->val);
right=hasPathSum(root->right,sum-root->val);
if(left||right)
return true;
else
return false;
}
}
};