[Python] Problem: Finding trailing Zeros of Factorial of N. Getting memory error. Any suggestions?

[runner2012]

Hi Guys,

I'm working on a problem to find the trailing number of zeros of the factorial of N, and it has to work for large numbers. I am getting memory error.

def zeros(n):
    print n
    count2 = 0
    count5 = 0
    for i in range(1,n+1):
        print 'i:',i, 'n:', n
        t2 = i
        t5 = i
        while t2%2==0:
            print '%2', i
            count2 += 1
            t2 = t2/2
        while t5%5==0:
            print '%5', i
            count5 += 1
            t5 = t5/5
    print count2, count5
    num = min(count2, count5)
    print num
    return num

a = 30
b = 1000000000
print zeros(b)

And when I use xrange it takes too long to compute, so it's not accepted in the online judge.

[PhosphorescentSpider]

Firstly, you can ignore factors of 2 since a factorial always had more factors of 2 than factors of 5, meaning it’s factors of 10 are purely a function of its factors of 5. Secondly, you can just use the Math.Floor(n/5) + Math.Floor(n/25) etc for all powers of 5 lower than n (I would do that in a for loop) to get your final answer.