how to remove even elements from list

[lastrial]

How to remove even elements from list without using a counter?

[Adak]

As was mentioned in a similar thread recently, a boolean value is one way. Just a flip-flop switch.

pseudo-code:
i = even = 0
while (array[i] has another element)  {
   if (even = 0)  {
        zero out that element of the array
        even = 1
   else
        even = 0
   } 
   increment i   
}

If you're asking how to do this without an i variable to scan through the subscript values, then I have no idea. You could use memory addresses (pointers), but that's just another form of a counter.

[lastrial]

I am talking about pointer lists

[whiteflags]

In a pedantic sense you could just start at one end of the list and free every other element. I assume odd items are first, but for example...

node *walk;
node *del;

while( walk != NULL && walk->next != NULL && walk->next->next != NULL ) {
   del = walk->next->next;
   walk = del->next;
   delete( del );
}

You might need to edit that if you need to look at node data to figure out what's even or odd.