Thread: A struct problem

Code:

#include <stdio.h>

struct Node
{
int index;
struct Node *next_in_line;
};

void print_list_in_reverse(struct Node * first_in_list);

int main(void)
{ 
struct Node n1={12,NULL};
struct Node n2={43,&n1};
struct Node n3={32,&n2};
struct Node n4={24,&n3};

print_list_in_reverse(&n4);

return 0;
}
void print_list_in_reverse(struct Node * p)
{
if(p == NULL)
return;
print_list_in_reverse(p->next_in_line);
printf("%i\t", p->data);
}

I don't get the "print_list_in_reverse" function ..
would anyone explain please?

First off: do you see how your Nodes are connected together?

If so, sit down with a piece of paper and trace out what happens. Note that *p is local to the function, so that each time you call the function p is different. The first time *p is n4; the second time *p is n4.next_in_line, which is n3; then it is n3.next_in_line which is n2, etc.

I understand how to type the list normally ..but not in reverse

Originally Posted by Salahuddin

I understand how to type the list normally ..but not in reverse

So read what's there: it's telling you how to print the list in reverse. But you do have to read it.

I'm sorry but i understand the mechanism but i don't understand the syntax

What does this code means ?

Code:

if(p == NULL)
return

And how can i use the function in it .. while defining it ?

Code:

print_list_in_reverse(p->next_in_line);

Originally Posted by Salahuddin

I'm sorry but i understand the mechanism but i don't understand the syntax

What does this code means ?

Code:

if(p == NULL)
return

What do you find confusing about this piece of code? It's an if statement.

Originally Posted by Salahuddin

And how can i use the function in it .. while defining it ?

Code:

print_list_in_reverse(p->next_in_line);

Look up recursion then.

ok .. it's an if statement ..
what does "return;" means?
I'm a beginner so calm down ..
Thanks

It means "return". It returns a value (or in this case no value, since it's a function-returning-nothing) to the function that called it.

PS: Beginner isn't an excuse for lazy.

So if (p==NULL) , the function won't continue but it will break right ??
it will not compile >>
print_list_in_reverse(p->next_in_line);
so we can write instead

Code:

if (p==NULL)
return;   //don't continue
else
print_list_in_reverse(p->next_in_line);
printf("%i\t", p->data);

i hope i got it ...

PS: Beginner isn't an excuse for lazy.

I agree with you but i think i'm doing my best to understand this simple code for you ..
Thanks again