Factorials

[M-a-S]

> "Andrew Wilkinson" <ajw126 at NOSPAMyork.ac.uk> wrote in message
> >
> > def fac(n):
> >     return reduce(long.__mul__, range(1,n+1), 1L)
> >
> > ..would probably be a bit quicker. I'm not sure how much quicker though.
> >
> > Anyway, hope this is of some use,
> > Regards,
> > Andrew Wilkinson

def factorial_rec(n):
  if n <= 1:
    return 1
  else:
    return n*factorial_rec(n-1)

def factorial_iter(n):
  s = 1
  for i in range(2,n+1):
    s *= i
  return s

def factorial_rdc(n):
  return reduce(long.__mul__, range(1,n+1), 1L)


Best times (seconds) on Compaq 5430US, Pentium 4, 1.8GHz, 512MB
Windows XP, Python 2.3 (#46, Jul 29 2003, 18:54:32) [MSC v.1200 32 bit (Intel)] on win32

Calculations of 950!, 1000 times each (xrange(1000)) --

recursion ..... 8.01
reduction ..... 4.20
iteration ..... 3.79

M-a-S