Problem with a linked list
I have a problem with this small program. It added some value to list. If I uncomment //printf("%d",first->val);
the program gives error. Everything seems to be ok ;(
#include <stdio.h>
#include <stdl开发者_高级运维ib.h>
typedef struct element {
struct element *next;
int val;
} el_listy;
el_listy *first = 0;
void add_to_list(el_listy *lista, int value)
{
if(lista == 0)
{
lista = malloc (sizeof(el_listy));
lista->val = value;
lista->next = 0;
printf("added as first \n");
}
else
{ printf("added as fsecond \n");
el_listy *wsk = lista,*tmp;
while(wsk->next != 0) wsk = wsk->next;
tmp = malloc (sizeof(el_listy));
tmp->val = value;
tmp->next = 0;
wsk->next = tmp;
}
}
int main ()
{
add_to_list(first,2);
add_to_list(first,4);
//printf("%d",*first->val);
system("pause");
return 0;
}
first->val
is just like (*first).val
, you can't use them both. also, as missingno said, add_to_list
never changes first
you should pass it's address as argument, not the pointer itself, meaningadd_to_list(&first,4);
(and change the implementation of add_to_list
as well)
Your program never changes the value of first
. It remains a null pointer and thus gives an error when dereferenced.
->
already follows a pointer, so the *
tries to treat first
as pointer to pointer to el_listy
. You might find cdecl
helpful.
You should use either (*first).val
or first->val
. Otherwise you get the wrong level of indirection.
Yes, it's a simple mistake.
fitsr won't change after *add_to_list()* function is called.
You should define function like this:
add_to_list(El_list **lista, ...)
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