LeetCode： Path Sum 2

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22, 
              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

This is a very elegant Solution: 

 1 class Solution {
 2 public:
 3     vector<vector<int> > solSet;
 4     vector<int> sol;
 5     void solve(TreeNode* root, int sum){
 6         if ( (root->left==NULL) && (root->right==NULL) && (sum-root->val==0) ) { 
 7             sol.push_back(root->val); 
 8             solSet.push_back(sol);      
 9             return;    
10         }
11         sol.push_back(root->val);
12         if (root->left !=NULL){
13             solve(root->left, sum-root->val);
14             sol.pop_back();        //记住需要pop_back
15         }
16         if (root->right!=NULL){
17         solve(root->right, sum-root->val);    
18         sol.pop_back();
19         }
20          
21     }
22      
23  
24     vector<vector<int> > pathSum(TreeNode *root, int sum) {
25         // Start typing your C/C++ solution below
26         // DO NOT write int main() function
27         sol.clear();
28         solSet.clear();
29         if (root==NULL) {return solSet;}
30         solve(root, sum);
31         return solSet;
32     }
33 };

This problem deserved  to be rehacking 

posted @ 2014-03-31 21:29  andyqee  阅读(193)  评论(0)  编辑  收藏  举报