二叉树的深度优先、广度优先遍历实现

递归深度优先：

  1 package xh_algorithm.chapter03;
  2 
  3 import java.util.Arrays;
  4 import java.util.LinkedList;
  5 
  6 /**
  7  * @author zsh
  8  * @site qqzsh.top
  9  * @create 2019-08-15 10:28
 10  * @description 二叉树的遍历
 11  * 递归实现
 12  */
 13 public class Main1 {
 14 
 15     /**
 16      * 创建二叉树
 17      * @param inputList 输入序列
 18      * @return
 19      */
 20     public static TreeNode createBinaryTree(LinkedList<Integer> inputList){
 21         TreeNode node = null;
 22         if (inputList == null || inputList.isEmpty()){
 23             return null;
 24         }
 25         Integer date = inputList.removeFirst();
 26         if (date != null){
 27             node = new TreeNode(date);
 28             node.leftChild = createBinaryTree(inputList);
 29             node.rightChild = createBinaryTree(inputList);
 30         }
 31         return node;
 32     }
 33 
 34     /**
 35      * 二叉树的前序遍历
 36      * @param node 二叉树节点
 37      */
 38     static void preOrderTraveral(TreeNode node){
 39         if (node == null){
 40             return;
 41         }
 42         //根左右
 43         System.out.println(node.data);
 44         preOrderTraveral(node.leftChild);
 45         preOrderTraveral(node.rightChild);
 46     }
 47 
 48     /**
 49      * 二叉树的中序遍历
 50      * @param node 二叉树节点
 51      */
 52     static void inOrderTreveral(TreeNode node){
 53         if (node == null){
 54             return;
 55         }
 56         //左根右
 57         inOrderTreveral(node.leftChild);
 58         System.out.println(node.data);
 59         inOrderTreveral(node.rightChild);
 60     }
 61 
 62     /**
 63      * 二叉树的后序遍历
 64      * @param node 二叉树节点
 65      */
 66     static void postOrderTreveral(TreeNode node){
 67         if (node == null){
 68             return;
 69         }
 70         //左右根
 71         postOrderTreveral(node.leftChild);
 72         postOrderTreveral(node.rightChild);
 73         System.out.println(node.data);
 74     }
 75 
 76     public static void main(String[] args) {
 77         LinkedList<Integer> inputList = new LinkedList<>(Arrays.asList(new Integer[]{
 78             3,2,9,null,null,10,null,null,8,null,4
 79         }));
 80         TreeNode treeNode = createBinaryTree(inputList);
 81         System.out.println("前序遍历");
 82         preOrderTraveral(treeNode);
 83         System.out.println("中序遍历");
 84         inOrderTreveral(treeNode);
 85         System.out.println("后序遍历");
 86         postOrderTreveral(treeNode);
 87     }
 88 }
 89 
 90 /**
 91  * 二叉树节点
 92  */
 93 class TreeNode{
 94     int data;
 95     TreeNode leftChild;
 96     TreeNode rightChild;
 97 
 98     public TreeNode(int data) {
 99         this.data = data;
100     }
101 }

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