Node Copying

 Node*  Node::deep_copy()  {
     Node  *r  =  new  Node(number);
     for  (Node  *c1  =  r,  *c2  =  next;  c2;
             c1  =  c1->next,  c2  =  c2->next)  {
         c1->next  =  new  Node(c2->number);
     }
     return  r;
 }