Solutions for Cassidoo Newsletter (July 26)

zerosEndingFactorial.py

#!/bin/bash
import math
import re

# There are a couple of solutions here, one that can be easily stepped through to understand the 
# process and allows for error checking to be introduced easily, the other a one liner just because 
# it's what the cool kids seem to be doing.

def zerosEndingFactorial(n):
    total = 1
    for i in range(n, 1, -1):
        total *= i

    counter = 0
    for i in range(len(str(total))-1, 1, -1):
        if str(total)[i] == "0":
            counter += 1
        else:
            break

    return counter

def zerosEndingFactorial2(n):
    return len(re.split('([1-9]+)',str(math.factorial(n)))[-1])

if __name__ == "__main__":
    print(zerosEndingFactorial(1))
    print(zerosEndingFactorial(5))
    print(zerosEndingFactorial(100))

    print(zerosEndingFactorial2(1))
    print(zerosEndingFactorial2(5))
    print(zerosEndingFactorial2(100))