【41】102. 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         vector<vector<int>> res;
14         if(!root) return res;
15         queue<TreeNode*> q;
16         q.push(root);
17         while(!q.empty()){
18             int size = q.size();
19             vector<int> level;
20             //level.clear();
21             for(int i = 0; i < size; i++){
22                 //vector<int> level;
23                 TreeNode* tmp = q.front();
24                 q.pop();
25                 level.push_back(tmp -> val);
26                 if(tmp -> left){
27                     q.push(tmp -> left);
28                 }
29                 if(tmp -> right){
30                     q.push(tmp -> right);
31                 }
32             }
33             res.push_back(level);
34         }
35         return res;
36     }
37 };