树的层次遍历（Java代码实现）

 1 public class Solution{
 2 class TreeNode {
 3     int val;
 4     TreeNode left;
 5     TreeNode right;
 6     TreeNode(int x) { val = x; }
 7 }
 8 public static void LaywerTraversal(TreeNode root){
 9         if(root==null) return;
10         LinkedList<TreeNode> list = new LinkedList<TreeNode>();  
11         list.add(root);
12         TreeNode currentNode;
13         while(!list.isEmpty()){
14             currentNode=list.poll();
15             System.out.println(currentNode.val);
16             if(currentNode.left!=null){
17                 list.add(currentNode.left);
18             }
19             if(currentNode.right!=null){
20                 list.add(currentNode.right);
21             }
22         }
23     }
24 }