从上往下打印出二叉树的每个结点，同一层的结点按照从左到右的顺序打印

题目：

解答：

首先创建BinaryTreeNode

 1 public class BinaryTreeNode {
 2     int data;
 3     BinaryTreeNode lchind;
 4     BinaryTreeNode rchind;
 5
 6     public BinaryTreeNode(int data) {
 7         this.data = data;
 8         lchind = null;
 9         rchind = null;
10     }
11
12     private int getData() {
13         return data;
14     }
15
16     private BinaryTreeNode getLchildNode() {
17         return lchind;
18     }
19
20     private void setLchildNode(BinaryTreeNode node) {
21         lchind = node;
22     }
23
24     private BinaryTreeNode getRchildNode() {
25         return rchind;
26     }
27
28     private void setRchildNode(BinaryTreeNode node) {
29         rchind = node;
30     }
31 }

接着：

 1 import java.util.*;
 2
 3 public class Solution {
 4
 5     public static void main(String[] args) {
 6         BinaryTreeNode node1=new BinaryTreeNode(8);
 7         BinaryTreeNode node2=new BinaryTreeNode(6);
 8         BinaryTreeNode node3=new BinaryTreeNode(10);
 9         BinaryTreeNode node4=new BinaryTreeNode(5);
10         BinaryTreeNode node5=new BinaryTreeNode(7);
11         BinaryTreeNode node6=new BinaryTreeNode(9);
12         BinaryTreeNode node7=new BinaryTreeNode(11);
13         node1.setLchildNode(node2);node1.setRchildNode(node3);
14         node2.setLchildNode(node4);node2.setRchildNode(node5);
15         node3.setLchildNode(node6);node3.setRchildNode(node7);
16
17         printFromTopToBottom(node1);
18     }
19
20     private static void printFromTopToBottom(BinaryTreeNode root) {
21         if(root == null) {
22             return;
23         }
24
25         Queue<BinaryTreeNode> queue = new LinkedList<BinaryTreeNode>();
26
27         queue.add(root);
28
29         while(!queue.isEmpty()) {
30             BinaryTreeNode node = queue.poll();
31             System.out.println(node.getData());
32
33             if(node.getLchildNode() != null) {
34                 queue.add(node.getLchildNode());
35             }
36
37             if(node.getRchildNode() != null) {
38                 queue.add(node.getRchildNode());
39             }
40         }
41     }
42 }

原文地址：https://www.cnblogs.com/wylwyl/p/10366253.html