From: Tanaka Akira <akr@...>
Date: 2012-02-17T22:55:31+09:00
Subject: Re: Factorial

2012/2/17 Junayeed Ahnaf Nirjhor <zombiegenerator@aol.com>:
>
> What is the most efficient way in Ruby to calculate the factorial of any
> given sum? Is there any way to make it as fast as in C?
>
> Complexity doesn't matter as long as it works correctly.

How about Math.gamma(n+1).to_i for fact(n) assuming n <= 22 ?

If the restriction, n <= 22 is not acceptable,
table lookup is another option.

I think C is not so useful here because fact(21) overflows 64bit signed int.
-- 
Tanaka Akira