Question

I was reading about a few basic operations on linked list and I saw two types of loops being used predominantly

---

struct node {
   int data;
   struct node *next;
}*start=NULL,*tmp;

The first loop was of the form

for(tmp=start;tmp->next!=NULL;tmp=tmp->next);

Using the above loop, now the tmp pointer points towards the last node in the list

The second loop was of the form

tmp=start;
while(tmp!=NULL)
{
     // do something
}

I think that both of them do the same work, but I’m not sure. Is there any difference?

Answer 1

I suppose your while loop is something like this.

temp=start;
while(temp!=NULL)
{
     // do something
     temp= temp->next;
}

In your code of for loop, When you are out of the for loop, temp is not pointing to NULL. temp is pointing to end of the linked list. But in case of while loop, your temp is pointing to NULL after you exit the while loop and you don’t have tail(Unless you assign temp to any other temporary variable to change the logic of program) with you if you want to use it in the further steps. That is the only difference. Except that there isn’t much difference.

You could have checked it by writing a small program and printing the results. I recommend you do it.