Path Sum Total Accepted: 50216 Total Submissions: 168425

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题目来自于leetcode

https://leetcode.com/problems/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.

              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.

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

Path Sum Total Accepted: 50216 Total Submissions: 168425

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原文地址：http://blog.csdn.net/zhouyelihua/article/details/45173373