Robin Koch wrote: > Am 02.01.2016 um 12:49 schrieb katye2...@gmail.com: > >> I'm trying to write a python program to find how many trailing zeros >> are in 100! (factorial of 100). I used factorial from the math >> module, but my efforts to continue failed. Please help. > > Using not Python, but math: > > Every "0" at the end of 100! represents a multiplication by the factor > 10 or the factors 2 and 5. > > There are 20 numbers with at least one factor 5. > There are 4 numbers with at least two factors 5 (=25). > There are no numbers with three factors 5 (=125). > > There are 50 numbers with at least one factor 2. > > So 100! contains 24 factors 5 and even more factors 2. > So 100! contains 24 facotrs 10 and therefore has 24 trailing zeros.
Spelt in Python: >>> def trailing_zeros_fact(n): ... total = 0 ... while n: ... n //= 5 ... total += n ... return total ... >>> trailing_zeros_fact(100) 24 >>> trailing_zeros_fact(math.factorial(100)) 23331553860986038170424809714066675122678992066095405367148240973804399998307478902235365994039129571563424480206805939562796302729215999999999999999999999901 -- https://mail.python.org/mailman/listinfo/python-list
