Linked List finding length - whats the difference between these two functions?

Is there any difference between these two functions? I mean in-terms of the result returned?

int Length(struct node* head) {
  struct node* current = head;
  int count = 0;

  while (current != NULL) {
    count++;
    current = current->next;
  }

  return count;
}

and this function

int Length(struct node* head) {
  int count = 0;

  w开发者_开发技巧hile (head != NULL) {
    count++;
    head = head->next;
  }

  return count;
}

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They are the same. One uses a local 'current' variable to iterate over the list, while the other one uses the same variable that was received through the function arguments.

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The returned value will be the same.

The former is the kind of code that would be written by a programmer subscribing to the style rule that says "it is bad practice to modify parameters because they are passed by value and would give the reader a false sense that the function would modify the corresponding argument."

Not necessarily bad advice. It makes the code a little longer, though, but it reads better. Many readers look at the second and have an initial reaction of "wait, what? changing the head? Oh... okay, no it's safe...."

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No difference. The second version simply uses the function argument itself as a variable to work with in the body, and that's perfectly legitimate. In fact, it's even slightly more efficient than the first version which make a gratuitous copy.

You couldn't use the second version if the argument were declared const, i.e. int Length(struct node* const head) -- but since it isn't, you're free to use the argument variable for your own purposes.