Difference between iterating to next node in recursive function vs recursive function call-CodePudding

In this piece of code, I am comparing two linked lists and checking whether the items in the linked lists are equal or not.

bool Check(Node *listA, Node *listB) {
   if (listA == NULL && listB == NULL)
      return true;

   if (listA->item == listB->item)
   {
      listA = listA->link;
      listB = listB->link;
      return Check(listA, listB);
   }
      return false;
}

I was wondering what the difference between this code:

listA = listA->link;
listB = listB->link;
return Check(listA, listB);

and this is:

return Check(listA->link, listB->link);

Both pieces of code produce the correct answer, but I can't seem to understand what the difference is.

CodePudding user response：

There is no difference, they do exactly the same thing. The only difference is that you could change something in the next node if you needed before calling Check(). But in your case they are exactly the same, the second option is cleaner tho so i recommend that one.

CodePudding user response：

In general, modifying an IN parameter value makes your function's code and intent less clear, so it's best to avoid it.

Also consider that if you are using a debugger and step back to a prior recursive call, you will not be able to see the correct node that was inspected, since its pointer was already overwritten. Thus it will be more confusing to debug.

Practically speaking, the outcome of both functions will be the same. The second one may be infinitesimally faster due to skipping the two pointless assignment operations, unless that is optimized away.