C++实现的链表类实例

#include <iostream>
using namespace std;
class linklist
{
  private:
     struct node
     {
      int data;
      node *link;
     }*p;
  public:
     linklist();
     void append( int num );
     void add_as_first( int num );
     void addafter( int c, int num );
     void del( int num );
     void display();
     int count();
     ~linklist();
};
linklist::linklist()
{
   p=NULL;
}
void linklist::append(int num)
{
  node *q,*t;
  if( p == NULL )
  {
   p = new node;
   p->data = num;
   p->link = NULL;
  }
  else
  {
   q = p;
   while( q->link != NULL )
      q = q->link;
   t = new node;
   t->data = num;
   t->link = NULL;
   q->link = t;
  }
}
void linklist::add_as_first(int num)
{
  node *q;
  q = new node;
  q->data = num;
  q->link = p;
  p = q;
}
void linklist::addafter( int c, int num)
{
  node *q,*t;
  int i;
  for(i=0,q=p;i<c;i++)
  {
   q = q->link;
   if( q == NULL )
   {
     cout<<"\nThere are less than "<<c<<" elements.";
     return;
   }
  }
  t = new node;
  t->data = num;
  t->link = q->link;
  q->link = t;
}
void linklist::del( int num )
{
  node *q,*r;
  q = p;
  if( q->data == num )
  {
   p = q->link;
   delete q;
   return;
  }
  r = q;
  while( q!=NULL )
  {
   if( q->data == num )
   {
     r->link = q->link;
     delete q;
     return;
   }
   r = q;
   q = q->link;
  }
  cout<<"\nElement "<<num<<" not Found.";
}
void linklist::display()
{
  node *q;
  cout<<endl;
  for( q = p ; q != NULL ; q = q->link )
    cout<<endl<<q->data;
}
int linklist::count()
{
  node *q;
  int c=0;
  for( q=p ; q != NULL ; q = q->link )
    c++;
  return c;
}
linklist::~linklist()
{
  node *q;
  if( p == NULL )
    return;
  while( p != NULL )
  {
   q = p->link;
   delete p;
   p = q;
  }
}
int main()
{
  linklist ll;
  cout<<"No. of elements = "<<ll.count();
  ll.append(12);
  ll.append(13);
  ll.append(23);
  ll.append(43);
  ll.append(44);
  ll.append(50);
  ll.add_as_first(2);
  ll.add_as_first(1);
  ll.addafter(3,333);
  ll.addafter(6,666);
  ll.display();
  cout<<"\nNo. of elements = "<<ll.count();
  ll.del(333);
  ll.del(12);
  ll.del(98);
  cout<<"\nNo. of elements = "<<ll.count();
  return 0;
}