Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

For example:

Given binary tree {3,9,20,#,#,15,7},

3   / \  9  20    /  \   15   7

return its level order traversal as:

[  [3],  [9,20],  [15,7]]

confused what "{1,#,2,3}" means?

Solution:

1 /** 2  * Definition for binary tree 3  * public class TreeNode { 4  *     int val; 5  *     TreeNode left; 6  *     TreeNode right; 7  *     TreeNode(int x) { val = x; } 8  * } 9  */10 public class Solution {11     public List
     
      
       > levelOrder(TreeNode root) {12         List
       
        
         > res = new ArrayList
         
          
           >();13 List
           
             oneRes = new ArrayList
            
             ();14 if (root==null){15 return res;16 }17 18 List
             
               lastLevel = new ArrayList
              
               ();19 lastLevel.add(root);20 oneRes.add(root.val);21 res.add(oneRes);22 List
               
                 curLevel;23 while (lastLevel.size()!=0){24 oneRes = new ArrayList
                
                 ();25 curLevel = new ArrayList
                 
                  ();26 for (int i=0;i