自定义二叉查找树基本操作

/**
 * @desc: 自定义二叉查找树： 插入键值对，根据key查找元素值，删除节点，取最大（小）的元素值，
 *                           前序（中序，后序，层次）遍历，树的高度
 * @author: 毛会懂
 * @create: 2021-01-05 14:11:00
 **/
public class MyBinaryFindTree<K extends Comparable<K>,V> {
    //头结点
    private Node root;
    //元素个数
    private Integer size;

    public MyBinaryFindTree() {
        this.root = null;
        size = 0;
    }

    //插入元素
    public void put(K key, V value){
        root = put(root,key,value);
    }

    //根据key，获取元素
    public V get(K key){
        return get(root,key);
    }

    //删除元素
    public void delete(K key){
         delete(root,key);
    }

    //元素的个数
    public Integer size(){
        return size;
    }

    //获取最大值
    public V getMax(){
        return getMax(root);
    }

    //获取最小值
    public V getMin(){
        return getMin(root);
    }

    //前序遍历
    public Queue<Node> getPreList(){
        Queue<Node> queue = new LinkedList<>();
        getPreList(root,queue);
        return queue;
    }

    //中序遍历
    public Queue<Node> getMidList(){
        Queue<Node> queue = new ArrayBlockingQueue<>(30);
        getMidList(root,queue);
        return queue;
    }

    //后序遍历
    public Queue<Node> getAfterList(){
        Queue<Node> queue = new ArrayDeque<>();
        getAfterList(root,queue);
        return queue;
    }

    //层次遍历
    public Queue<Node> getLayerList(){
        Queue<Node> queue = new ArrayDeque<>();
        Queue<Node> temp = new ArrayDeque<>();
        temp.add(root);
        while (!temp.isEmpty()){
            //取队头的元素
            Node element = temp.poll();
            queue.add(element);
            if(element.left != null){
                temp.add(element.left);
            }
            if(element.right != null){
                temp.add(element.right);
            }
        }
        return queue;
    }

    //树的最大深度
    public Integer getTop(){
        return getTop(root);
    }

    private Node put(Node node,K key,V value){
        if(node == null){
            node = new Node(key,value,null,null);
            size++;
            return node;
        }
        if(key.compareTo(node.key) < 0){
            //插入的结点小于当前结点，则继续查找左节点
            node.left = put(node.left,key,value);
        }else if(key.compareTo(node.key) > 0){
            //插入的结点大于当前结点，则继续查找右节点
            node.right = put(node.right,key,value);
        }else{
            //插入的结点等于当前结点， 则值替换
            node.value = value;
        }
        return node;
    }

    private V get(Node node,K key){
        if(node == null){
            return null;
        }
        if(key.compareTo(node.key) < 0){
            //查找的key在左节点
            return get(node.left,key);
        }else if(key.compareTo(node.key) > 0){
            //查找的key在右节点
            return get(node.right,key);
        }else{
            return node.value;
        }
    }

    private Node delete(Node node,K key){
        if (node == null){
            return null;
        }
        if(key.compareTo(node.key) < 0){
            node.left = delete(node.left,key);
        }else if(key.compareTo(node.key) > 0){
            node.right = delete(node.right,key);
        }else{
            //待删除的结点为当前的node结点。
            size--;
            //如果没有右子树，直接返回左子树
            if(node.right == null){
                return node.left;
            }
            //如果没有左子树，直接返回右子树
            if(node.left == null){
                return node.right;
            }

            //先找此结点右节点最小的结点，它的父结点指向为null。
            Node minNode = node.right;
            while (minNode.left != null){
                minNode = minNode.left;
            }
            //找最小结点的上一个结点
            Node preMinNode = node;
            if(preMinNode.right.left !=null) {
                preMinNode = preMinNode.right;
                while (preMinNode.left.left != null) {
                    preMinNode = preMinNode.left;
                }
            }
            preMinNode.left = null;

            //最小的结点左右结点重新指向 待删结点的左右结点。
            minNode.left = node.left;
            minNode.right = node.right;

            //待删除的父结点指向最小的结点。
            node = minNode;

        }
        return node;
    }

    //获取最大值
    private V getMax(Node node){
        if(node == null){
            return null;
        }
        while (node.right != null){
            node = node.right;
        }
        return node.value;
    }

    //获取最小值
    private V getMin(Node node){
        if(node == null){
            return null;
        }
        if(node.left != null){
            return getMin(node.left);
        }else{
            return node.value;
        }
    }

    //前序遍历
    private void getPreList(Node node,Queue<Node> queue){
        if(node == null){
            return;
        }
        queue.add(node);
        getPreList(node.left,queue);
        getPreList(node.right,queue);
    }

    //中序遍历
    private void getMidList(Node node,Queue<Node> queue){
        if(node == null){
            return;
        }
        getMidList(node.left,queue);
        queue.add(node);
        getMidList(node.right,queue);
    }

    //后序遍历
    private void getAfterList(Node node,Queue<Node> queue){
        if(node == null){
            return;
        }
        getAfterList(node.left,queue);
        getAfterList(node.right,queue);
        queue.add(node);
    }

    //树高
    private Integer getTop(Node node){
        if(node == null){
            return 0;
        }
        Integer leftMax = 0;
        Integer rightMax = 0;
        if(node.left != null) {
            leftMax = getTop(node.left);
        }
        if(node.right != null){
            rightMax = getTop(node.right);
        }
        return leftMax > rightMax ? leftMax + 1: rightMax + 1;
    }

    //遍历的时候用到，所以修饰符为public
    public class Node{
        private K key;
        private V value;
        private Node left;
        private Node right;

        public Node(K key, V value, Node left, Node right) {
            this.key = key;
            this.value = value;
            this.left = left;
            this.right = right;
        }

        //遍历的时候用到
        public K getKey(){
            return key;
        }

        //遍历的时候用到
        public V getValue(){
            return value;
        }
    }
}

验证代码：

public class Main {
    //构造二叉查找树，并查找
    public static void main(String[] args) {
        MyBinaryFindTree<Integer,String> myTree = new MyBinaryFindTree<>();
        myTree.put(10,"张10");
        myTree.put(8,"张8");
        myTree.put(15,"张15");
        myTree.put(5,"张5");
        myTree.put(3,"张3");
        myTree.put(6,"张6");
        myTree.put(12,"张12");
        myTree.put(20,"张20");
        myTree.put(4,"张4");
        System.out.println("树的大小=" + myTree.size());
        System.out.println("二叉查找树，查找元素3对应的值：" + myTree.get(3));
        myTree.delete(6);
        System.out.println("树的大小=" + myTree.size());
        System.out.println("最大的值：" + myTree.getMax());
        System.out.println("最小的值：" + myTree.getMin());

        System.out.println("前序遍历：");
        Queue<MyBinaryFindTree<Integer, String>.Node> preList = myTree.getPreList();
        for (MyBinaryFindTree<Integer, String>.Node node : preList){
            System.out.print(node.getValue() +"  ");
        }
        System.out.println("---------");

        System.out.println("中序遍历：");
        Queue<MyBinaryFindTree<Integer, String>.Node> midList = myTree.getMidList();
        for (MyBinaryFindTree<Integer, String>.Node node : midList){
            System.out.print(node.getKey() +"  ");
        }
        System.out.println("---------");

        System.out.println("后序遍历：");
        Queue<MyBinaryFindTree<Integer, String>.Node> afterList = myTree.getAfterList();
        for (MyBinaryFindTree<Integer, String>.Node node : afterList){
            System.out.print(node.getValue() +"  ");
        }
        System.out.println("---------");

        System.out.println("层次遍历：");
        Queue<MyBinaryFindTree<Integer, String>.Node> layerList = myTree.getLayerList();
        for (MyBinaryFindTree<Integer, String>.Node node : layerList){
            System.out.print(node.getKey() +"  ");
        }
        System.out.println("---------");
        System.out.println("树高：" + myTree.getTop());
    }
}