102. 二叉树的层次遍历

 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     {
14         vector<vector<int>> vec;
15         if(root == NULL)
16             return vec;       
17         queue<TreeNode*> que;
18         que.push(root);       
19         while(!que.empty())
20         {
21             int size = que.size();
22             vector<int> vec_temp;           
23             while(size--)
24             {
25                 TreeNode* t = que.front();
26                 vec_temp.push_back(que.front()->val);
27                 que.pop();            
28                 if(t->left)
29                     que.push(t->left);
30                 if(t->right)
31                     que.push(t->right);
32             }
33             vec.push_back(vec_temp);
34         }
35         return vec;
36     }
37 };