From: Rob Biedenharn <Rob@...>
Date: 2008-07-04T01:14:15+09:00
Subject: Re: pseudo-randomize an array in a consistent order

On Jul 3, 2008, at 11:57 AM, Max Williams wrote:

> Thanks guys
>
> This is what i did in the meantime since asking (I monkey-patched
> Array):
>
> class Array
>
>  def randomize(seed=nil)
>   srand(seed) if seed
>   self.sort{|a,b| rand <=> rand }
>  end
>
>  def randomize!(seed=nil)
>   srand(seed) if seed
>   self.sort!{|a,b| rand <=> rand }
>  end
>
> end
>
> I'm worried though that using sort like this is a bit inefficient.   
> The
> array being sorted is around 3000 numbers (and not likely to exceed
> 5000) so maybe that's not too much of an issue.  Is there a more
> efficient way you can think of?


Use sort_by{rand} and you'll call rand once per element (O(n)) rather  
than twice per comparison (O(n*log(n)))

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com