实现链表数据结构

实现链表数据结构

#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;
}