二分搜索树删除最大元素最小元素

package tree;

import java.util.*;

//具有可比性的泛型
public class BST<E extends Comparable> {
    
    
    private class Node {
    
    
        public E e;
        private Node left;
        private Node right;

        public Node(E e) {
    
    
            this.e = e;
            left = null;
            right = null;
        }
    }

    private Node root;
    private int size;

    public BST() {
    
    
        root = null;
        size = 0;
    }

    public int size() {
    
    
        return size;
    }

    public boolean isEmpty() {
    
    
        return size == 0;
    }

    //    向二分搜索树中添加新的元素
//    public void add(E e){
    
    
//        if (root == null){
    
    
//            root = new Node(e);
//            size++;
//        }else {
    
    
//            add(root, e);
//        }
//    }
    //向以node为根的二分搜索树中插入元素 递归算法
//    private void  add(Node node,E e){
    
    
//        if(e.equals(node.e))
//            return;
//        else if (e.compareTo(node.e)<0&&node.left==null){
    
    
//            node.left = new Node(e);
//            size++;
//            return;
//        }
//        else if (e.compareTo(node.e)>0&&node.right==null){
    
    
//            node.right = new Node(e);
//            size++;
//            return;
//        }
//        if (e.compareTo(node.e)<0){
    
    
//            add(node.left,e);
//        }else
//            add(node.right,e);
//    }
    public void add(E e) {
    
    
        root = add(root, e);
    }

    private Node add(Node node, E e) {
    
    
        if (node == null) {
    
    
            size++;
            return new Node(e);
        }
        if (e.compareTo(node.e) < 0) {
    
    
            node.left = add(node.left, e);
        } else if (e.compareTo(node.e) > 0) {
    
    
            node.right = add(node.right, e);
        }
        return node;
    }

    // 是否包含某个节点
    public boolean contains(E e) {
    
    
        return contains(root, e);
    }

    private boolean contains(Node node, E e) {
    
    
        if (node == null) {
    
    
            return false;
        }
        if (e.compareTo(node.e) == 0) {
    
    
            return true;
        } else if (e.compareTo(node.e) < 0) {
    
    
            return contains(node.left, e);
        } else {
    
    
            return contains(node.right, e);
        }
    }

    //遍历
    //先序遍历根左右
    public void proOrder(){
    
    
        preOrder(root);
    }
    private void preOrder(Node node){
    
    
        if (node==null){
    
    
            return;
        }
        System.out.println(node.e);
        preOrder(node.left);
        preOrder(node.right);
    }
    //遍历
    //先序遍历根左右 非递归算法
    public void proOrderNR() {
    
    
        Stack<Node> stack = new Stack<>();
        stack.push(root);
        while (!stack.isEmpty()) {
    
    
            Node cur = stack.pop();
            System.out.println(cur.e);

            if (cur.right!=null){
    
    
                stack.push(cur.right);
            if (cur.left!=null)
                stack.push(cur.left);
            }
        }
    }

    //中序遍历
    public void inOrder() {
    
    
        inOrder(root);
    }

    private void inOrder(Node node) {
    
    
        if (node == null)
            return;
        inOrder(node.left);
        System.out.println(node.e);
        inOrder(node.right);
    }

    //后续遍历
    public void postOrder() {
    
    
        postOrder(root);
    }

    private void postOrder(Node node) {
    
    
        if (node == null) {
    
    
            return;
        }
        postOrder(node.left);
        postOrder(node.right);
        System.out.println(node.e);

    }

    //查找二分搜索树的最小值（向左走，最后一个左子树）
    public E minimum(){
    
    
        if (size == 0)
            throw new IllegalArgumentException("BST is empty");
        return minimum(root).e;
    }

    private Node minimum(Node node) {
    
    
        if (node.left ==null){
    
    
            return node;
        }

        return minimum(node.left);
    }
    //查找二分搜索树的最大值（向右走，最后一个右子树）
    public E maxmum(){
    
    
        if (size==0)
            throw new IllegalArgumentException("BST is empty");
        return maxmum(root).e;
    }

    private Node maxmum(Node node) {
    
    
        if (node.right==null)
            return node;
        return maxmum(node.right);
    }

    //删除二分搜索树的最小值，返回最小值
    public E removeMin(){
    
    
        E ret=minimum();
        removeMin(root);
        return ret;
    }

//最小节点删除之后，将其右节点添加到删除的位置
    private Node removeMin(Node node) {
    
    
        if (node.left==null){
    
    
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

//删除最大值
    public E removeMax(){
    
    
        E ret = maxmum();
        removeMax(root);
        return ret;
    }

    private Node removeMax(Node node) {
    
    
        if (node.right==null){
    
    
            Node leftNode = node.left;
            node.left=null;
            size--;
            return leftNode;
        }
        node.right = removeMax(node.right);
        return node;
    }


    @Override
    public String toString() {
    
    
        StringBuilder stringBuilder = new StringBuilder();
        generateBSTString(root, 0, stringBuilder);
        return stringBuilder.toString();
    }

    //    以node为根节点，深度为depth描述二叉树的字符串
    private void generateBSTString(Node node, int depth, StringBuilder stringBuilder) {
    
    
        if (node == null) {
    
    
            stringBuilder.append(generateBSTString(depth) + "null\n");
            return;
        }
        stringBuilder.append(generateBSTString(depth) + node.e + "\n");
        generateBSTString(node.left, depth + 1, stringBuilder);
        generateBSTString(node.right, depth + 1, stringBuilder);
    }

    private String generateBSTString(int depth) {
    
    
        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < depth; i++) {
    
    
            stringBuilder.append("--");
        }
        return stringBuilder.toString();
    }
    //层序遍历（广度）
    public void levelOrder(){
    
    
        Queue<Node> queue = new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()){
    
    
            Node cur = queue.remove();
            System.out.println(cur.e);

            if (cur.left!=null){
    
    
                queue.add(cur.left);
            }
            if (cur.right!=null){
    
    
                queue.add(cur.right);
            }
        }
    }
    public static void main(String[] args) {
    
    

        BST<Integer> bst = new BST<>();
        Random random = new Random();
        int n = 1000;
        for (int i = 0; i < n; i++) {
    
    
            bst.add(random.nextInt(10000));
        }
        ArrayList<Integer> nums = new ArrayList<>();
        while (!bst.isEmpty()){
    
    
            nums.add(bst.removeMin());
        }
        System.out.println(nums);

        for (int i = 1; i < nums.size(); i++) {
    
    
            if (nums.get(i-1)>nums.get(i))
                throw new IllegalArgumentException("Error");
        }
        System.out.println("removeMin test completed");


        ArrayList<Integer> nums1 = new ArrayList<>();
        while (!bst.isEmpty()){
    
    
            nums1.add(bst.removeMax());
        }
        System.out.println(nums);

        for (int i = 1; i < nums1.size(); i++) {
    
    
            if (nums.get(i-1)<nums1.get(i))
                throw new IllegalArgumentException("Error");
        }
        System.out.println("removeMin test completed");
    }
}