(leetcode)Binary Tree Level Order Traversal

 1 /**
 2  * Definition for a binary tree node.
 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 public:
12     vector<vector<int>> levelOrder(TreeNode* root) {
13         queue<TreeNode*> que;
14         vector<vector<int>> ret;
15         if(!root) return ret;
16         int cur,next;
17         que.push(root);
18         cur = 1;next = 0;
19         vector<int> tmp;
20         while(!que.empty())
21         {
22             TreeNode* tmpNode;
23             tmpNode = que.front();
24             tmp.push_back(tmpNode->val);
25             que.pop();
26             cur--;
27             if(tmpNode->left) { que.push(tmpNode->left); next++; }
28             if(tmpNode->right) { que.push(tmpNode->right); next++; }
29             if(cur == 0) { cur = next; next = 0; ret.push_back(tmp); tmp.clear(); }
30             
31         }
32         
33         return ret;
34     }
35 };