Question

I have been asked this question once or twice in interviews. I am not sure whether it’s possible or not. Maybe structures in C are a way out? Can anyone elaborate on this further?

Answer 1

If the two values are inside a structure, then you can use the function’s return value instead of passing by reference:

struct twoNumbers {
  int first;
  int second;
};

struct twoNumbers swapNumbers(struct twoNumbers src)
{
  int tmp = src.first;
  src.first = src.second;
  src.second = tmp;
  return src;
}

/* ... */

struct twoNumbers s = { 5, 42 };

s = swapNumbers(s);

…though even then it’s probably more practical to use pointers.