LeetCode学习篇二十三——Path Sum

题目：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.

通过率：32.7% 难度：medium

这道题由于是二叉树，而且是判断根结点到叶节点的和，所以直接对树进行深搜即可，代码如下：

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:

bool search(TreeNode* root, int sum, int t) {
if(root == NULL) return false;
if(root->left == NULL && root->right== NULL)  {
return t+root->val == sum;
}
return search(root->left, sum, t+root->val) || search(root->right, sum, t+root->val);
}

bool hasPathSum(TreeNode* root, int sum) {
return search(root, sum, 0);

}
};