# Leetcode 112. Path Sum

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

``````/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     struct TreeNode *left;
*     struct TreeNode *right;
* };
*/
bool hasSum(struct TreeNode* root, int sum,int pathsum)
{
if(root->left==NULL&&root->right==NULL)
{
if(pathsum+root->val==sum)return true;
else return false;
}
bool pathleft=false,pathright=false;
if(root->left!=NULL)
pathleft=hasSum(root->left,sum,pathsum+root->val);
if(root->right!=NULL)
pathright=hasSum(root->right,sum,pathsum+root->val);
if(pathleft||pathright)
return true;
else
return false;
}
bool hasPathSum(struct TreeNode* root, int sum) {
if(root==NULL)return false;
return hasSum(root,sum,0);
}
``````