C++实现循环链表

practice6.h文件

#ifndef PRACTICE4_H_INCLUDED
#define PRACTICE4_H_INCLUDED

#include<iostream>
//循环链表
template <class Type> class List;//申明友元类的前置声明
template<class Type> class ListIterator;//申明友元类的前置声明
template<class Type>
class ListNode   //节点类
{
 friend class List<Type>;
 friend class ListIterator<Type>;
 private:
  Type data;
  ListNode *link;
  ListNode(Type);  //构造函数
  ListNode() {}
};


template<class Type>
class List
{
    friend class ListIterator<Type>;
 public:
     List(){first=new ListNode<Type>;first->link=first;}; // 一个空的链表  表头 只有一个表头
     void Insert(Type);

     void Delete(Type);

 private:
    ListNode<Type> *first;
};
template<class Type>
class ListIterator
{
public:
    ListIterator(const List<Type>& l):list(l),current(l.first->link){};//构造函数，参数是链表，这个链表的迭代器   初始化链表和指针
    bool NotNull();
    bool NextNotNull();
    Type*First();
    Type*Next();


private:
    const List<Type> &list;//链表 迭代器是哪个链表的
    ListNode<Type> *current;//指针，指向链表里的节点

};

template <class Type>//判断非空
bool ListIterator<Type>::NotNull()
{

    if(current!=list.first)  return true;
    else return false;
}

template <class Type>//判断下一个非空
bool ListIterator<Type>::NextNotNull()
{

    if(current->link!=list.first)  return true;
    else return false;

}

template <class Type>//取first的值
Type*ListIterator<Type>::First()
{

    if(current!=list.first)   return &current->data;
    else return 0;
}

template <class Type>//判断下一个是否为空
Type *ListIterator<Type>::Next()
{

        current=current->link;
        if (current==list.first)  current=current->link;
        return &current->data;
}

template<class Type>//构造函数
ListNode<Type>::ListNode(Type element)
{
    data=element;
    link=0;
}
template <class Type>//插入
void List<Type>::Insert(Type k)
{

    ListNode<Type> *newnode=new ListNode<Type>(k);
    newnode->link=first->link;
    first->link=newnode;

}



template<class Type>//删除节点
void List<Type>::Delete(Type k)
{

    ListNode<Type> *previous=first;//前一个的指针
    ListNode<Type> *current;
    for(current=first->link;(current!=first)&&current->data!=k;
    previous=current,current=current->link)
    {
      ;
    }
    if(current!=first)
    {
        //if(previous) previous->link=current->link;
        //else first=first->link;
        previous->link=current->link;
        delete current;
    }
}





#endif // PRACTICE4_H_INCLUDED

practice3.cpp文件

#include<iostream>
#include "practice6.h"
#include<list>
using namespace std;
int main()
{

    List<int> intList;

    intList.Insert(5);
    intList.Insert(15);

    intList.Insert(25);
    intList.Insert(35);


   // cout<<"这是标准c++stl中的链表和迭代器"<<endl;
    //std::list<int> listIntegers;
   // listIntegers.push_front(5);
   // listIntegers.push_front(15);
   // listIntegers.push_front(25);
   // listIntegers.push_front(35);

   // std::list<int>::iterator i=listIntegers.begin();
    //while(i!=listIntegers.end())
   // {
    //    cout<<*i<<"->";
    //    ++i;

   // }
    //cout<<endl;
    cout<<"这是我的链表和迭代器"<<endl;




//    if(li.NotNull())
//    {
//        cout<<*li.First();
//        while(li.NextNotNull())
//            cout<<"->"<<*li.Next();
//        cout<<endl;
//    }
    cout<<"测试一下循环"<<endl;
    ListIterator<int> iter(intList);
    cout<<*iter.First()<<endl;
    cout<<*iter.Next()<<endl;
    cout<<*iter.Next()<<endl;
    cout<<*iter.Next()<<endl;

    cout<<*iter.Next()<<endl;
    cout<<*iter.Next()<<endl;
    cout<<*iter.Next()<<endl;
    cout<<*iter.Next()<<endl;



    return 0;
}