Which one is better and why?

[rjddude1]

Is recursive function for calculating Fibonacci series or iterative function is better?
ITERATIVE:

int fibonacci_iterative(int n)      //Iterative formula for fibonacci series
{
  int f0 = 0;
  int f1 = 1;
  int i, fn;
 
  if (n == 0)
        return 0;
  if (n == 1)
        return 1;
 
  for(i = 2; i <= n; i++)
  {
    fn = f0 + f1;
    f0 = f1;
    f1 = fn;
  }
  return f1;
}
 

RECURSIVE

int fibonacci_recursive(int nNumber)   //Recursive formula for fibonacci series
{
    if (nNumber == 0)
        return 0;
    if (nNumber == 1)
        return 1;
    return fibonacci_recursive(nNumber-1) + fibonacci_recursive(nNumber-2);
}
 

[donbock]

The stack usage for the iterative function is invariant -- it is the same regardless of the input argument.

The stack usage for the recursive function is proportional to the input value.

The recursive function is smaller and easier to understand.

I haven't done an analysis, but it looks to me like the recursive function will be slower than the iterative function.

Which is "better"? It is a trade-off between these factors. In some contexts, ease of understanding will trump everything else; in other contexts (most notably embedded systems), stack usage trumps everything else.