Java--算法--二叉树

1. 二叉树的基本介绍：
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      1. package com.model.tree;
         
         import java.util.ArrayDeque;
         import java.util.Deque;
         
         /**
          * @Description:测试类
          * @Author: 张紫韩
          * @Crete 2021/8/17 21:50
          * 树的遍历
          */
         public class TreeDemo02 {
             public static void main(String[] args) {
                 TreeNode root = new TreeNode(0);
                 TreeNode left = new TreeNode(1);
                 TreeNode right = new TreeNode(2);
                 TreeNode  left_left = new TreeNode(3);
                 TreeNode right_right = new TreeNode(4);
                 root.left=left;
                 root.right=right;
                 left.left=left_left;
                 right.right=right_right;
         //        preOrder(root);
         //        midOrder(root);
         //        postOrder(root);
                 sequenceOrder(root);
         
             }
         // 层序遍历
             public static void sequenceOrder(TreeNode root){
                 if (root==null){
                     return;
                 }
                 Deque<TreeNode> deque=new ArrayDeque<>();
                 deque.add(root);
                 while (!deque.isEmpty()){
                     TreeNode cur = deque.pop();
                     System.out.println(cur);
                     if (cur.left!=null){
                         deque.add(cur.left);
                     }
                     if (cur.right!=null){
                         deque.add(cur.right);
                     }
                 }
             }
         
         
         //    先序遍历方式
             public static void preOrder(TreeNode root){
                 if (root==null){
                     return;
                 }
                 System.out.println(root);
                 preOrder(root.left);
                 preOrder(root.right);
             }
         
             public static void midOrder(TreeNode root){
                 if (root==null){
                     return;
                 }
                 midOrder(root.left);
                 System.out.println(root);
                 midOrder(root.right);
             }
             public static void postOrder(TreeNode root){
                 if (root==null){
                     return;
                 }
                 postOrder(root.left);
                 postOrder(root.right);
                 System.out.println(root);
             }
         }

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