自己实现一个二叉查找树BinarySearchTree

需求

自己实现一个简单的二叉查找树BinarySearchTree

二叉排序树或者是一棵空树，或者是具有下列性质的二叉树：

• 若左子树不空，则左子树上所有结点的值均小于或等于它的根结点的值；
• 若右子树不空，则右子树上所有结点的值均大于或等于它的根结点的值；
• 左、右子树也分别为二叉排序树；

图示

包含功能：

• insert
• remove
• contains
• findMax
• findMin
• toString

代码：

import java.util.NoSuchElementException;import java.util.StringJoiner;public class BinarySearchTree<T extends Comparable<? super T>> {    private BinaryNode<T> root;    public BinarySearchTree() {        root = null;    }    public BinarySearchTree(T[] arr) {        for (T t : arr) {            insert(t);        }    }    public void markEmpty() {        root = null;    }    public boolean isEmpty() {        return root == null;    }    public boolean contains(T t) {        return contains(t, root);    }    public T findMin() {        if (isEmpty())            throw new NoSuchElementException();        return findMin(root).element;    }    public T findMax() {        if (isEmpty())            throw new NoSuchElementException();        return findMax(root).element;    }    public void insert(T t) {        root = insert(t, root);    }    public void remove(T t) {        root = remove(t, root);    }    @Override    public String toString() {        StringJoiner joiner = new StringJoiner(" ", "[", "]");        listAll(this.root, joiner);        return joiner.toString();    }    private void listAll(BinaryNode<T> node, StringJoiner joiner) {        if (node.left != null)            listAll(node.left, joiner);        joiner.add(node.element.toString());        if (node.right != null)            listAll(node.right, joiner);    }    private boolean contains(T t, BinaryNode<T> node) {        if (node == null)            return false;        int compareResult = t.compareTo(node.element);        if (compareResult < 0)            return contains(t, node.left);        else if (compareResult > 0)            return contains(t, node.right);        else            return true;    }    private BinaryNode<T> findMin(BinaryNode<T> node) {        if (node == null)            return null;        if (node.left == null)            return node;        return findMin(node.left);    }    private BinaryNode<T> findMax(BinaryNode<T> node) {        if (node == null)            return null;        while (node.right != null)            node = node.right;        return node;    }    private BinaryNode<T> insert(T t, BinaryNode<T> node) {        if (node == null)            return new BinaryNode<T>(t);        int compareResult = t.compareTo(node.element);        if (compareResult < 0)            node.left = insert(t, node.left);        else if (compareResult > 0)            node.right = insert(t, node.right);        return node;    }    private BinaryNode<T> remove(T t, BinaryNode<T> node) {        if (node == null)            return null;        int compareResult = t.compareTo(node.element);        if (compareResult < 0) {            node.left = remove(t, node.left);        } else if (compareResult > 0) {            node.right = remove(t, node.right);        } else if (node.left != null && node.right != null) {            // two children            node.element = findMin(node.right).element;            node.right = remove(node.element, node.right);        } else {            node = (node.left != null) ? node.left : node.right;        }        return node;    }    private static class BinaryNode<T> {        T element;        BinaryNode<T> left;        BinaryNode<T> right;        public BinaryNode(T element) {            this(element, null, null);        }        public BinaryNode(T element, BinaryNode<T> left, BinaryNode<T> right) {            this.element = element;            this.left = left;            this.right = right;        }    }}