尾插法链表

不使用循环，采用头尾指针，不带有头结点，我这里只是简易的输出，并没有写专用的迭代器。

#include <iostream>

using namespace std;

template<class T> class MyList;

template<class T>
class ListNode
{
    friend class MyList<T>;
private:
    T data;
    ListNode *Link;
    ListNode(const T &thedata){data = thedata; Link=0;}
    ListNode(){}
};

template<class T>
class MyList
{
public:
    MyList(){first = new ListNode<T>;first->Link=NULL;tail=first;}
    ~MyList(){MakeEmpty();}
    void MakeEmpty();
    bool IsEmpty();
    void Insert(const T &);
    void Delete(const T &);
    void Invert();
    void Concatenate(MyList<T>);
    void Show();
private:
    ListNode<T> *first;
    ListNode<T> *tail;
};

template<class T>
bool MyList<T>::IsEmpty()
{
    return first == 0;
}

template<class T>
void MyList<T>::MakeEmpty()
{
    ListNode<T> *p=first;
    while(first)
    {
        p = first;
        first = first->Link;
        delete p;
    }
}

template<class T>
void MyList<T>::Insert(const T &x)
{
    ListNode<T> *newNode = new ListNode<T>(x);
    newNode->Link=tail->Link;
    tail->Link = newNode;
    tail = newNode;
}

template<class T>
void MyList<T>::Delete(const T &k)
{
    if(IsEmpty()) return;
    ListNode<T> *previous=0;
    ListNode<T> *current;
    for(current=first;current&&current->data!=k;
        previous=current,current=current->Link);
    if(current)
    {
        if(previous) previous->Link=current->Link;
        else first->Link=tail;
        delete current;
    }
}

template<class T>
void MyList<T>::Invert()
{
    ListNode<T> *p=first->Link, *q=0;
    while(p)
    {
        ListNode<T> *r = q; q = p;
        p = p->Link;
        q->Link = r;
    }
    first->Link = q;
}

template<class T>
void MyList<T>::Concatenate(MyList<T> List2)
{
    if(!first) {first = List2.first;}
    if(List2.first)
    {
        ListNode<T> *p;
        for(p=first; p->Link; p=p->Link);
        p->Link = List2.first->Link;
    }
}


template<class T>
void MyList<T>::Show()
{
    ListNode<T> *current;
    for(current=first->Link; current; current=current->Link)
    {
        cout << current->data;
        if(current->Link) cout << "->";
    }
    cout << endl;
}

int main()
{
    MyList<int> intlist;
    intlist.Insert(5);
    intlist.Insert(15);
    intlist.Insert(25);
    intlist.Insert(35);
    intlist.Invert();
    MyList<int> intlist2;
    intlist2.Insert(45);
    intlist.Concatenate(intlist2);
    intlist.Show();
    intlist.Delete(35);
    intlist.Delete(25);
    intlist.Delete(15);
    intlist.Delete(6);

    intlist.Show();
//    cout << "Hello world!" << endl;
    return 0;
}