链表

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int maxn=1e5+5;
class List; //前视定义,否则友元无法定义
class LinkNode
{
    friend  List; //链表结点类的定义
private:
    LinkNode *link;
    int data;
public:
    LinkNode(const int & item, LinkNode *ptr = NULL)
    {
        data=item;
        link=ptr;
    }
    LinkNode (LinkNode *ptr = NULL)
    {
        link=ptr;
    }
    ~LinkNode() { };
};
class List
{
    //单链表类的定义
private:
    LinkNode *first; //指向首结点的指针
public:
    List ()
    {
        first = new LinkNode ();
    }
    ~List ()
    {
        MakeEmpty();   //析构函数
    }
    void MakeEmpty ( );      //链表置空
    int Remove (int i);     //需要补充的成员函数
    void input(int endTag);
    void output();      //需要补充的成员函数
};

void List:: MakeEmpty ( )
{
    LinkNode *q;
    while ( first->link != NULL )
    {
        q = first->link;
        first->link = q->link;
        delete q;
    }
};
void List :: input (int endTag)
{
    LinkNode  *newnode,*last;
    last=new LinkNode (0);
    first->data=0;
    int val;
    cin>>val;
    while(val!=endTag)
    {
        newnode=new LinkNode (val);
        last->link=newnode;
        last=newnode;
        if(first->data==0)
        {
            first->data=-1;
            first->link=newnode;
        }
        cin>>val;
    }
}
int List :: Remove(int index)
{
    cout<<"remove"<<endl;
    //cout<<first->link<<endl;
    //if(first==NULL)
        //return 0;
    LinkNode  *q=first,*last;
    int cnt=0;
    while(q->link!=NULL&&cnt<index)
    {
        last=q;
        q=q->link;
        cnt=cnt+1;
    }
    if(q->link==NULL&&cnt!=index)
    {
        cout<<"Error!!!"<<endl;
        return -1;
    }
    last->link=q->link;
    return 0;

}
void List :: output()
{
    //cout<<first->link<<endl;
    LinkNode  *q=first,*last;
    //cout<<"答案是"<<endl;
    // cout<<first->data<<" ";
    while(q->link!=NULL)
    {
        q = q->link;
        cout<<q->data<<" ";
    }
    cout<<endl;
}
int main()
{
    List l;
    l.input(0); //0为输入的结束数字
    l.output ();
    int index;
    cin>>index; //要删除的元素的下标，下标从0 开始
    l.Remove(index);
    l.output (); //删除后输出
    l.MakeEmpty();
    return 0;

}