层次遍历二叉树

 

import java.util.ArrayList; import java.util.List;import java.util.Queue;import java.util.concurrent.LinkedBlockingDeque;/**public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;     public TreeNode(int val) {        this.val = val;     } }*/public class Solution {     public ArrayList
     
       PrintFromTopToBottom(TreeNode root) {        List
      
        list = new ArrayList
       
        ();         if(root==null)            return (ArrayList
        
         ) list;        Queue
         
           queue = new LinkedBlockingDeque
          
           (); queue.add(root); while(queue.size()>0){ TreeNode node05 = queue.poll(); list.add(node05.val); if(node05.left!=null) queue.add(node05.left); if(node05.right!=null) queue.add(node05.right); } return (ArrayList
           
            ) list; }}