Binary tree sort tree is also called binary search number. It is either an empty number or a binary tree with the following properties:

① If the left subtree is not empty, the values of all nodes on the left subtree are smaller than the values of its root nodes;

② If the right subtree is not empty, the values of all nodes on the right subtree are greater than the values of their root nodes;

③ The left and right subtrees are also binary sorting trees

Implementation method:

package com.tongtong.tree;

import java.util.LinkedList;
import java.util.Queue;

/**
 * Implementation of binary sort (search) tree
 */
public class BinaryTree {

    private Node root;
    public BinaryTree(){
        root = null;
    }
    //Insert data into the sort binary tree
    public void insert(int data){
        Node newNode = new Node(data);
        if(root == null){
            root = newNode;
        }else{
            Node current = root;
            Node parent; //Each master node
            while(true){ //Find where to insert
                parent = current;
                if(data < current.data){
                    current = current.left;
                    if(current == null){
                        parent.left = newNode;
                        return;
                    }
                }else{
                    current = current.right;
                    if(current == null){
                        parent.right = newNode;
                        return;
                    }
                }
            }
        }
    }

    //Building a binary tree with numerical input
    public void buildTree(int[] data){
        for(int i=0;i<data.length;i++){
            insert(data[i]);
        }
    }

    //Recursive implementation of middle order traversal method -- > left root right
    public void inOrder(Node localRoot){
        if(localRoot != null){
            inOrder(localRoot.left);
            System.out.print(localRoot.data + " ");
            inOrder(localRoot.right);
        }
    }

    public void inOrder(){
        inOrder(this.root);
    }

    //Recursive implementation of preorder traversal method
    public void preOrder(Node localRoot){
        if(localRoot != null){
            System.out.print(localRoot.data + " ");
            preOrder(localRoot.left);
            preOrder(localRoot.right);
        }
    }

    public void preOrder(){
        preOrder(this.root);
    }

    //Recursive implementation of postorder traversal method -- > left and right roots
    public void postOrder(Node localRoot){
        if(localRoot != null){
            postOrder(localRoot.left);
            postOrder(localRoot.right);
            System.out.print(localRoot.data + " ");
        }
    }

    public void postOrder(){
        postOrder(this.root);
    }

    //level traversal
    public void layerTranverse(){
        if(this.root == null){
            return;
        }

        Queue<Node> q = new LinkedList<Node>();
        q.add(this.root);
        while(!q.isEmpty()){
            Node n = q.poll();
            System.out.print(n.data);
            System.out.print(" ");
            if(n.left != null) q.add(n.left);
            if(n.right != null) q.add(n.right);
        }
    }

    public static void main(String[] args) {
        BinaryTree biTree = new BinaryTree();
        int[] data = {2,8,7,4,9,3,1,6,7,5};
        biTree.buildTree(data);

        System.out.println("Middle order traversal of binary trees========");
        biTree.inOrder();
        System.out.println();
        System.out.println("Preorder traversal of binary trees========");
        biTree.preOrder();
        System.out.println();
        System.out.println("Binary Tree Postorder Traversal ========");
        biTree.postOrder();
        System.out.println();
        System.out.println("level traversal============");
        biTree.layerTranverse();
    }
}