void sort_d_list( struct d_list *head )
{
   struct d_list *p, *head1, *p1, *p2, *pre;
   p = head;
   head1 = NULL;
   p2 = NULL;
   while( p != NULL )
   {
      pre = p->next;
      p->next = NULL;
      if( head1 == NULL )
           head1 = p;
      else
      {
         p1 = head1;
         p2 = NULL;
         while( (p1!=NULL) && (p->data > p1->data) )
         {
            p2 = p1;
            p1 = p1->next;
         }
         if( p2 == NULL )
         {
            p->next = head1;
            head1 = p;
         }
         else
         {
            p->next = p1;
            p2->next = p;
         }
      }
      p = pre;
   }
   //return head1;
}