java数据结构-二叉排序树(删除只有一个子节点的节点，删除有两个节点的节点)

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package com.demo4;

public class Node {
    int value;
    Node left;
    Node right;
    public Node(int value){
        this.value = value;
    }

    public void add(Node node) {
        if(node == null){
            return;
        }
        if(node.value > this.value){
            if(this.right == null){
                this.right = node;
            }
            else{
                this.right.add(node);
            }
        }
        if(node.value < this.value){
            if(this.left == null){
                this.left = node;
            }
            else{
                this.left.add(node);
            }
        }
    }

    public void middleshow(Node node) {
        if(node == null){
            return;
        }
        middleshow(node.left);
        System.out.println(node.value);
        middleshow(node.right);
    }

    public Node search(int value) {
        if(this.value == value){
            return this;
        }
        else if(value < this.value){
            if(this.left == null) {
                return null;
            }
            return left.search(value);
        }
        else{
            if(this.right == null){
                return null;
            }
            return right.search(value);
        }
    }

    public Node searchParent(int value) {
        if((this.left != null && this.left.value == value) || (this.right != null && this.right.value == value)){
            return this;
        }
        else{
            if(this.value > value && this.left != null){
                return this.left.searchParent(value);
            }
            else if(this.right != null){
                return this.right.searchParent(value);
            }
            else{
                return null;
            }
        }
    }
}

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package com.demo4;

public class BinarySearchTree {
    Node root;
    public void add(Node node){
        if(root == null){
            root = node;
        }
        else{
            root.add(node);
        }
    }
    public void middleshow(){
        if(root == null){
            System.out.println("This tree is Empty.");
            return;
        }
        else{
            root.middleshow(root);
        }
    }
    public Node search(int value){
        if(root == null) return null;
        else{
            return root.search(value);
        }
    }
    public Node searchParent(int value){
        if(root == null) return null;
        else{
            return root.searchParent(value);
        }
    }
    public void delete(int value){
        if(root == null){
            return;
        }

        else{
            Node target = search(value);
            if(target == null){
                return;
            }
            Node parent = searchParent(value);
            if(target.left == null && target.right == null){
                if(parent.left.value == value){
                    parent.left = null;
                }
                else{
                    parent.right = null;
                }
            }//有两个子节点
            else if(target.left != null && target.right != null){
                int min = deleteMin(target.right);
                target.value = min;
            }
            else {
                if(target.left != null){
                    if(parent.left.value == value){
                        parent.left = target.left;
                    }
                    else{
                        parent.right = target.left;
                    }
                }
                else{
                    if(parent.right.value == value){
                        parent.right = target.right;
                    }
                    else{
                        parent.left = target.right;
                    }
                }
            }

        }


    }

    private int deleteMin(Node node) {
        Node target = node;
        while (target.left != null){
            target = node.left;
        }
        delete(target.value);
        return target.value;
    }
}

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public class testBST {
    public static void main(String[] args) {
        int [] arr = new int[] {7,3,10,12,5,1,9};
        BinarySearchTree bst = new BinarySearchTree();
        for(int i : arr){
            bst.add(new Node(i));
        }
        System.out.println(bst.root.value);
        bst.delete(bst.root.value);
        System.out.println("**************************************************删除后");
        System.out.println(bst.root.value);