Linked List

Mistro116@yahoo.com · 12-04-2005, 04:23 PM

Hello,

Could someone please post some code for freeing all the nodes of a linked list in the most efficient manner.

The nodes pointer to next have to be referenced to null and then freed. I keep getting errors when I try to implement it.

I know its simple. Could anyone please post the code please?

Thanks,
Mistro116

Edit:

The code I have so far is:

Code:

void DeleteList (NODEPTR headPtr)
{
   NODEPTR curr, prev;
   
   if (IsEmpty (headPtr))
   {
      printf ("\nThe list is empty - All nodes have been ");
      printf ("deleted and freed.\n\n");
   }
   else
   {
      prev = NULL;
      
      curr = headPtr;
      
      while (prev != NULL)
      {
	 /*  Traverse the list.  */
	 prev = curr;
	 curr = curr -> next;
	 
	 prev -> next = NULL;
	 free (prev);
      }
      
      /*  Insert the node, temp, at the end of the list.  */
      headPtr = NULL;
   }
}

graemef · 12-04-2005, 04:46 PM

Two thing that I spotted:

The first is your while condition should be on curr not prev. prev is initiated to NULL and so you'd never enter the loop anyway.

The second is the you don't need to set prev->next to NULL since you are about to free the memory anyway.

hope that helps,

graeme.

Mistro116@yahoo.com · 12-04-2005, 05:02 PM

Are you sure we don't need to set prev's --> next equal to NULL? I was told to do this as a safety precaution. It might avoid segementation faults and memory leaks????

And yes I caught that error with the loop (prev should be curr) right after I posted this, and the code worked.

But yes so far so good, thanks.

Mistro116

graemef · 12-04-2005, 05:09 PM

Well I can't think why you would need it, because the very next statement is free'ing the memory and so you should not try and access anything that prev points to. However I'm open to persuasion

graeme.