Path Sum

每次用递归都怕栈溢出
 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */

10 class Solution {
11 private: map<int,bool> sums;
12 public:
13     bool hasPathSum(TreeNode *root, int sum) {
14         // Start typing your C/C++ solution below
15         // DO NOT write int main() function
16         if(root==NULL)
17         return false;
18         sums.clear();
19         sums[sum] = false;
20         addSum(root,0);
21         return sums[sum];
22     }
23     
24     void addSum(TreeNode *root,int pre)
25     {
26         if(root->left==NULL && root->right==NULL)
27         {
28             sums[pre+root->val] = true;
29         }
30         if(root->left!=NULL)
31         {
32             addSum(root->left,pre+root->val);
33         }
34         if(root->right!=NULL)
35         {
36             addSum(root->right,pre+root->val);
37         }
38     }
39 };