Re: [Dev-C++] linked lists...

[<or...@vp...>]

Hello j b!

Monday, November 18, 2002, 8:16:12 PM, you wrote:

jb> i  tried  to  write  a  code  using  linked lists to implement the
jb> multiplication  and  addition  of twp polynomials but it seems i'm
jb> not  very  successfull  cause  my pop funcition doesn't do what it
jb> should  and  i  don't  know  why i get that access violation error
jb> ..could any one help??

> /* definitions*/
>
> typedef struct node{
>   int coefficient;
>   int exponent;
>   struct node *next;
> }node;
>
> typedef struct stack{
>   node *firstptr;
> }stack;
>
> /*and the pop function*/
> 
> node *pop(stack *s){
>   node *nptr=new node;
>   if(nptr==NULL){
>     cout<<"exhausted memory"<<endl;
>     exit(1);
>   }
>   else{
>     nptr->coefficient=s->firstptr->coefficient;
>     nptr->exponent=s->firstptr->exponent;
>     s->firstptr=s->firstptr->next;//that's the problematic part
>   }
>   return nptr;
> }

Well  the  above code shouldn't give an access violation error, IF the
push  (I  assume you have a function named like that) works fine. So I
think the problem is with the push function.

And  one  more  thing. I don't know much about C++, but I'm good at C,
and  I  think  you should clean up memory when you detatch a node from
the list.

Something like:

node *pop(stack *s){
   node *ntmp; /* Temporary pointer */
   ...
   else{
     ...
     ntmp = s->firstptr;  /*!*/
     s->firstptr=s->firstptr->next; //that's the problematic part
     free(ntmp);          /*!*/
   }
   return nprt;
}

OR:
===
Why  not  return only a pointer to the node, instead of creating a new
one?
Then the code would be:

node *pop(stack *s){
   node *nptr; /* Only a pointer */
   nptr = s->firstptr;
   s->firstptr=s->firstptr->next;
   return nptr;
}

Of  course  you  will  need  to  free  the node that you get, from the
outside.

As  I  stated above, I don't know much about C++, but I've heard, that
there  are  many  built-in functions, and "things" inside C++ for list
creation. (They are created through templates, as I remember). Look in
the book.

-- 
Best regards,
 Oroszi Balázs                     mailto:or...@vp...

PGP-FP: FB80 8A43 2664 6126 E465  46E2 2546 CFA3 C25B 9F70
finger -l or...@se...