C++实现双向链表

#include<iostream>
using namespace std;
class DblList;

class DblListNode
{

    friend class DblList;
public:
    int data;
    DblListNode *llink,*rlink;
};

class DblList
{
public:
    DblList()
    {
        first=new DblListNode();
        first->llink=first->rlink=first;
    }
    void Insert(DblListNode*,DblListNode*);
    void Delete(DblListNode*);
//private:
public:
    DblListNode *first;
};

void DblList::Insert(DblListNode *p,DblListNode *x)//p表示新插入的节点插入x节点的右边
{
    p->llink=x;
    p->rlink=x->rlink;
    x->rlink->llink=p;
    x->rlink=p;
}
void DblList::Delete(DblListNode *x)
{

    if(x==first)
        cout<<"cant"<<endl;
    else{
        x->llink->rlink=x->rlink;
        x->rlink->llink=x->llink;
        delete x;
    }
}

int main()
{
    cout<<"ok"<<endl;
    DblList intList;
    DblListNode *node1,*node2,*node3,*node4,*node5;
    node1=new DblListNode();//创建的时候用new，那么就可以用deldete删除，否则报错
     node2=new DblListNode();
      node3=new DblListNode();
       node4=new DblListNode();
        node5=new DblListNode();
    node1->data=10;
    node2->data=20;
    node3->data=30;
    node4->data=40;
    node5->data=50;
    intList.Insert(node1,intList.first);//指针所以加&
    intList.Insert(node2,intList.first);
    intList.Insert(node3,intList.first);
    intList.Insert(node4,intList.first);
    intList.Insert(node5,intList.first);
    cout<<intList.first->rlink->data<<endl;
    cout<<intList.first->rlink->rlink->data<<endl;
    cout<<intList.first->rlink->rlink->rlink->data<<endl;

    intList.Delete(node4);
     cout<<intList.first->rlink->data<<endl;
    cout<<intList.first->rlink->rlink->data<<endl;
    cout<<intList.first->rlink->rlink->rlink->data<<endl;
    return 0;
}