Path Sum 深度搜索

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.

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/**
* 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) {

if(root==NULL)        //路不通
return false;
if(sum-root->val==0 && root->left==NULL && root->right==NULL)    //结束条件
return true;
if(hasPathSum(root->left,sum-root->val))
return true;
else
return hasPathSum(root->right,sum-root->val);
}
};