二叉查找树

 /* 主题：二叉查找树
* 作者：PhoenixZq
* 邮箱：zhouqiang312@126.com
* 开发语言：C++
* 开发环境：VC++ 6.0

* 时间：2010.12.10
*/

//BinarySearchTree.h
#ifndef BINARYSEARCHTREE_H
#define BINARYSEARCHTREE_H
#include <iostream>
typedef int T;
//template <class T>
class BinarySearchTree{
private:
    struct BinaryNode{
        T elem;
        BinaryNode *left;
        BinaryNode *right;

        BinaryNode(const T & theElem,BinaryNode *lt,BinaryNode *rt)
            :elem(theElem),left(lt),right(rt) {}
    };

public:
    BinaryNode *root;
    BinarySearchTree(BinaryNode *r = NULL):root(r){}//默认构造函数
    BinarySearchTree(const BinarySearchTree &rhs)//拷贝构造函数
        :root(rhs.root){}
    const BinarySearchTree & operator=(const BinarySearchTree & rhs){
        if(this != &rhs){
            makeEmpty(root);
            root = clone(rhs.root);
    }
        return *this;
    }
    ~BinarySearchTree(){
        makeEmpty(root);
    }

    BinaryNode * clone(BinaryNode * t)const{
        if(t == NULL)
            return NULL;
        return new BinaryNode(t->elem,clone(t->left),clone(t->right));
    }
    void insert(const T & x,BinaryNode * & t);
    void remove(const T & x,BinaryNode * & t);
    const T findMin(BinaryNode *t)const;
    const T findMax(BinaryNode *t)const;
    bool contains(const T & x,BinaryNode *t)const;
    void makeEmpty(BinaryNode * & t);
    void printTree(BinaryNode *t)const;
//    void makeEmpty();


/*    const T & findMin() const;
    const T & findMax() const;
    bool contains(const T & x) const;
    bool isEmpty() const;
    void printTree() const;
    void makeEmpty();
    void insert(const T & x);
    void remove(const T & x);
*/
};

#endif

#include "BinarySearchTree.h"
#include <iostream>
using namespace std;

void BinarySearchTree::makeEmpty(BinaryNode * & t){
    if(t != NULL){
        makeEmpty(t->left);
        makeEmpty(t->right);
        delete t;
    }
    t = NULL;
}

bool BinarySearchTree::contains(const T & x,BinaryNode *t)const{
    if(t == NULL) return false;
    else if(x < t->elem) 
        return contains(x,t->left);
    else if(x > t->elem)
        return contains(x,t->right);
    else return true;
}
//递归findMin
const T BinarySearchTree::findMin(BinaryNode *t)const{
    if(t == NULL) return NULL;
    if(t->left == NULL) return t->elem;
    return findMin(t->left);
}
//非递归findMax
//template <class T>
const T BinarySearchTree::findMax(BinaryNode *t)const{
    if(t != NULL)
        while(t->right != NULL)
            t = t->right;
    return t->elem;
}

//template <class T>
void BinarySearchTree::insert(const T & x,BinaryNode * & t){
    if(t == NULL) 
        t = new BinaryNode(x,NULL,NULL);
    else if(x < t->elem)
        insert(x,t->left);
    else if(x > t->elem)
        insert(x,t->right);
    else
        ;
}

//template <class T>
void BinarySearchTree::remove(const T & x,BinaryNode * & t){
    if(t == NULL)
        return ;
    if(x < t->elem)
        remove(x,t->left);
    else if(x > t->elem)
        remove(x,t->right);
    else if(t->left != NULL && t->right != NULL){
        t->elem = findMin(t->right);
        remove(t->elem,t->right);
    }
    else{
        BinaryNode *oldNode = t;
        t=(t->left != NULL) ? t->left:t->right;
        delete oldNode;
    }
}

void BinarySearchTree::printTree(BinaryNode *t)const{
    if(t != NULL){
        printTree(t->left);
        cout << t->elem << " ";
        printTree(t->right);
    }
}

int main(){
    BinarySearchTree BST;
    T data;
    int choice;
    while(true){
        system("cls");
        cout << "\n\n\n                              ---主界面---\n\n\n";
        cout << "                 1. 插入操作                  2. 删除操作\n";
        cout << "                 3. 查找操作                  4. 寻找最大值\n";
        cout << "                 5. 寻找最小值                6. 打印树\n";
        cout << "                 0. 退出\n";
        cout << " 请选择操作: ";
        cin >> choice;
        switch(choice){
        case 0:
            return 0;
        case 1:
            system("cls");
            cout << "请输入要插入的元素: " ;
            cin >> data;
            BST.insert(data,BST.root);
            break;
        case 2:
            system("cls");
            cout << "请输入要删除的元素: ";
            cin >> data;
            BST.remove(data,BST.root);break;
        case 3:
            system("cls");
            cout << "请输入要查找的元素: ";
            cin >> data;
            BST.contains(data,BST.root);break;
        case 4:
            system("cls");
            cout << "寻找最大值: ";
            BST.findMax(BST.root);break;
        case 5:
            system("cls");
            cout << "寻找最小值: ";
            BST.findMax(BST.root);break;
        case 6:
            system("cls");
            cout << "打印出树: ";
            BST.printTree(BST.root);system("pause");break;
        }    
    }
    return 0;
}

存在问题：

1.没能把root设置为私有；

2.插入节点操作之前没有创建二叉树.