Python Better Way to Express This Recursive Function

Question

Python version 2.7.6

I wrote an iterative function that computes the number of trailing zeros expected with a particular factorial. I then tried to rewrite it as a recursive function. This is the recursive result:

def f_FactorialTailZeros(v_Num, v_Result = 0):
    if v_Num < 5:
        return v_Num
    v_Result = v_Result + f_FactorialTailZeros(v_Num // 5, v_Num // 5)
    return v_Result

print(f_FactorialTailZeros(30)) ## 7
print(f_FactorialTailZeros(70)) ## 16

It works, but, for the sake of learning, is there a better way?

I don't see any problem at all with the way you have defined the recursive function. Offtopic: the prefix notation is something to avoid nowadays. — bgusach
– bgusach, Commented Jun 23, 2015 at 7:09

LittleQ · Accepted Answer · 2015-06-23 07:19:01Z

3

Based on your code:

def f_FactorialTailZeros(v_Num):
    if v_Num < 5:
        return 0
    return v_Num // 5 + f_FactorialTailZeros(v_Num // 5)

answered Jun 23, 2015 at 7:19

LittleQ

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2 Comments

JayJay123 Over a year ago

Yeah, that's the ticket. And I see where I went off track as well, which is the most important thing. Thanks.

Lawrence H Over a year ago

Yes, I think this is optimal. The beauty of recursion lies in the fact that you shouldn't need to keep track of state. Plus, passing in duplicate parameters to a function should also raise a red flag. Good job OP for coming up with the recursive solution though! It's pretty neat and not immediately obvious until you see it.

Kavin Eswaramoorthy · Accepted Answer · 2015-06-23 07:16:39Z

2

Yes, you can do it with recursive function have a look at following code and FYI read this

def recursive_trailingZeroes(A):
    if A==0:
        return 0
    return (A//5)+recursive_trailingZeroes(A//5)

edited Jun 23, 2015 at 7:16

answered Jun 23, 2015 at 7:12

Kavin Eswaramoorthy

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2 Comments

The6thSense Over a year ago

SO already finished the iterative method he wants to do it in recursive way

JayJay123 Over a year ago

Thanks, however, I have an iterative version that works. I wanted to know if there were a better recursive version than the one that I wrote.

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