微软算法100题16 按层遍历二叉树
第16 题：
题目（微软）：
输入一颗二元树，从上往下按层打印树的每个结点，同一层中按照从左往右的顺序打印。
例如输入
8
/ \
6 10
/ \ / \
5 7 9 11
输出8 6 10 5 7 9 11
思路：遇到这种按层执行或者按次序执行的动作，一般会联想到队列
1 package com.rui.microsoft; 2 3 import java.util.ArrayDeque; 4 import java.util.Deque; 5 6 public class Test16_TraverseTreeHorizontal { 7 8 public static void main(String[] args) { 9 Node node4 = new Node(4); 10 Node node3 = new Node(3); 11 Node node5 = new Node(5); 12 Node node2 = new Node(2); 13 14 node4.left = node3; 15 node4.right = node5; 16 node3.left = node2; 17 18 Test16_TraverseTreeHorizontal.traverse(node4); 19 } 20 21 public static void traverse(Node node){ 22 Node head = node; 23 24 if(null == head) return; 25 //leaf 26 if(null == head.left && null == head.right){ 27 System.out.println(head.value); 28 return; 29 } 30 31 //Non-leaf 32 Deque<Node> queue = new ArrayDeque<Node>(); 33 queue.offer(head); 34 35 while(!queue.isEmpty()){ 36 Node n = queue.poll(); 37 System.out.println(n.value); 38 Node left = n.left; 39 Node right = n.right; 40 if(null != left)queue.offer(left); 41 if(null != right)queue.offer(right); 42 } 43 44 } 45 46 static class Node{ 47 int value; 48 Node left; 49 Node right; 50 Node(int v){ 51 this.value = v; 52 } 53 } 54 }
