ACM-数据结构-二叉搜索树（C++实现）

近日研习《计算机算法》，一点点弄明白了二叉搜索树。

/*
@header      BSTree
@abstract    BSTree
@discussion  Insert,delete,search and order
@author      WalterBright,2016
*/

#include <iostream>
using namespace std;
template <class Type>
class BSTree;           //模板类作为友元类需提前声明
template <class Type>
class TreeNode{
public:
    friend class BSTree<Type>;
private:
    TreeNode *lChild;
    TreeNode *rChild;
    Type data;
};

template <class Type>
class BSTree{
public:
    BSTree(){
        tree=NULL;
    }
    ~BSTree(){
        delete tree;
    }
    TreeNode<Type>* Search(Type x);
    TreeNode<Type>* ISearch(Type x);
    void Insert(Type x);
    void Delete(Type x);
    void InOrder();        //中序遍历
    void PreOrder();       //先序遍历
    void PostOrder();      //后序遍历 （等价于先搜索右时的先序的反序）
private:
    TreeNode<Type> *tree;
    TreeNode<Type>* Search(TreeNode<Type> *t,Type x);
    void Delete(TreeNode<Type> *t,Type x);
    void Visit(TreeNode<Type> *t);
    void InOrder(TreeNode<Type> *t);
    void PreOrder(TreeNode<Type> *t);
    void PostOrder(TreeNode<Type> *t);
};
template <typename Type>
TreeNode<Type>* BSTree<Type>::Search(Type x){
    return Search(tree,x);
}
template <typename Type>
TreeNode<Type>* BSTree<Type>::Search(TreeNode<Type> *t,Type x){
    bool found=false;
    while(t&&!found){
        if(x==t->data){
            found=true;
        }
        else if(x<t->data){
            t=t->lChild;
        }
        else{
            t=t->rChild;
        }
    }
    if(found){
        return t;
    }
    else{
        return NULL;
    }
}

template <typename Type>
void BSTree<Type>::Visit(TreeNode<Type> *t){
    cout<<t->data<<‘ ‘;
}

template <typename Type>
void BSTree<Type>::Insert(Type x){
    bool found=false;
    TreeNode<Type> *p=tree,*q; //q是p的父节点
    while((p)&&(!found)){
        q=p;          //保证了p接下来往下走
        if(x==p->data){
            found=true;
        }
        else if(x<p->data){
            p=p->lChild;
        }
        else{
            p=p->rChild;
        }
    }
    if(!found){
        p=new TreeNode<Type>;
        p->lChild=p->rChild=NULL;
        p->data=x;
        if(tree){
            if(x<q->data){
                q->lChild=p;
            }
            else{
                q->rChild=p;
            }
        }
        else{
            tree=p;
        }
    }
}

template <typename Type>
void BSTree<Type>::Delete(Type x){
    Delete(tree,x);
}

template <typename Type>
void BSTree<Type>::Delete(TreeNode<Type> *t,Type x){
    bool found=false;
    TreeNode<Type> *p=t,*q;
    while((p)&&(!found)){
        if(x==p->data){
            found=true;
            break;
        }
        q=p;
        if(x<p->data){
            p=p->lChild;
        }
        else{
            p=p->rChild;
        }
    }
    if(found){         //用指针的引用可以节省代码量？
            if(p->lChild==NULL&&p->rChild==NULL){  //删除叶子
                if(x<=q->data){
                    q->lChild=NULL;
                }
                else{
                    q->rChild=NULL;
                }
                p=NULL;
            }
            else if(p->lChild==NULL){  //删除只包含右节点的节点
                if(x<=q->data){
                    q->lChild=p->rChild;
                }
                else{
                    q->rChild=p->rChild;
                }
                p=NULL;
            }
            else if(p->rChild==NULL){   //删除只包含左节点的节点
                if(x<=q->data){
                    q->lChild=p->lChild;
                }
                else{
                    q->rChild=p->lChild;
                }
                p=NULL;
            }
            else{                      //迭代删除
                q=p;
                p=p->lChild;
                while(p->rChild){
                    p=p->rChild;
                }
                x=(q->data)=(p->data);
                q=q->lChild;
                Delete(q,x);
            }

    }
}

template <typename Type>
void BSTree<Type>::InOrder(){
    InOrder(tree);
    cout<<endl;
}

template <typename Type>
void BSTree<Type>::PreOrder(){
    PreOrder(tree);
    cout<<endl;
}

template <typename Type>
void BSTree<Type>::PostOrder(){
    PostOrder(tree);
    cout<<endl;
}

template <typename Type>
void BSTree<Type>::InOrder(TreeNode<Type> *t){
    if(t){
        InOrder(t->lChild);
        Visit(t);
        InOrder(t->rChild);
    }
}

template <typename Type>
void BSTree<Type>::PreOrder(TreeNode<Type> *t){
    if(t){
        Visit(t);
        PreOrder(t->lChild);
        PreOrder(t->rChild);
    }
}

template <typename Type>
void BSTree<Type>::PostOrder(TreeNode<Type> *t){
    if(t){
        PostOrder(t->lChild);
        PostOrder(t->rChild);
        Visit(t);
    }
}

int main(){
    BSTree<int> bst1;
    bst1.Insert(80);/*              80          */
    bst1.Insert(90);/*             /  \         */
    bst1.Insert(60);/*            60  90        */
    bst1.Insert(70);/*           /  \           */
    bst1.Insert(20);/*          20  70          */
    bst1.Insert(10);/*         /  \             */
    bst1.Insert(40);/*        10  40            */
    bst1.Insert(30);/*           /  \           */
    bst1.Insert(50);/*          30  50          */
    bst1.InOrder();
    bst1.PreOrder();
    bst1.PostOrder();
    cout<<endl;

    bool s1=bst1.Search(40);cout<<s1<<endl;
    bool s2=bst1.Search(55);cout<<s2<<endl;

    bst1.InOrder();
    bst1.Delete(30);
    bst1.InOrder();
    return 0;
}