How would you write a non-recursive algorithm to calculate factorials?

Question

How would you write a non-recursive algorithm to compute n!?

Answer 1

assuming you wanted to be able to deal with some really huge numbers, I would code it as follows. This implementation would be for if you wanted a decent amount of speed for common cases (low numbers), but wanted to be able to handle some super hefty calculations. I would consider this the most complete answer in theory. In practice I doubt you would need to compute such large factorials for anything other than a homework problem

#define int MAX_PRECALCFACTORIAL = 13;

public double factorial(int n) {
  ASSERT(n>0);
  int[MAX_PRECALCFACTORIAL] fact = {1, 1, 2, 6, 24, 120, 720, 5040, 40320, 
                362880, 3628800, 39916800, 479001600};
  if(n < MAX_PRECALCFACTORIAL)
    return (double)fact[n];

  //else we are at least n big
  double total = (float)fact[MAX_PRECALCFACTORIAL-1]
  for(int i = MAX_PRECALCFACTORIAL; i <= n; i++)
  {
    total *= (double)i;  //cost of incrimenting a double often equal or more than casting
  }
  return total;

}