From: eden li <eden.li@...>
Date: 2007-04-24T18:47:51+09:00
Subject: Re: Shuffle Method

rand(3) - 1 always returns -1, 0 or 1 which is what sort() expects.
However, as Daniel points out, this method favors certain positions
for certain elements, so it won't give you a "true" shuffle.

On Apr 24, 10:16 am, Ari Brown <a...@aribrown.com> wrote:
> On Apr 22, 2007, at 11:15 PM, eden li wrote:
>
> > Why not just do a random sort instead?
> >>> some_array = ['cat', 'dog', 'fun', 'zoo']
> > => ['cat', 'dog', 'fun', 'zoo']
> >>> some_array.sort { rand(3) - 1 }
> > => ["zoo", "dog", "fun", "cat"]
>
> I wanted to write my own method to better understand how it works.
> Plus because it WAS fun, until it decided it didn't want to work.
>
> P.S. = why rand(3) - 1? Why not just some other rand(x)?
>
>
>
> >> --------------------------------------------------------------|
> >> SOURCE 1
> >> --------------------------------------------------------------|
> >> some_array= ['cat', 'dog', 'fun', 'zoo']
>
> >> def shuffle some_array
> >>    recurssive_shuffle some_array
> >> end
>
> >> def recurssive_shuffle some_array
> >>    n = some_array.length
> >>    helper_array = []
> >>    new_array = []
> >>    while n != 0
> >>      r = rand(n)
> >>      while some_array.length != (r + 1)
> >>        helper_array.push some_array.pop
> >>      end
> >>      new_array.push some_array.pop
> >>      n = (n - 1)
> >>      helper_array.each do |item|
> >>        some_array.push item
> >>      end
> >>    end
> >>    puts new_array
> >> end
>
> >> shuffle some_array
> >> --------------------------------------------------------------|
> >> SOURCE 2
> >> --------------------------------------------------------------|
> >> some_array = ['cat', 'dog', 'fun', 'zoo']
>
> >> def shuffle some_array
> >>    recurssive_shuffle some_array
> >> end
>
> >> def recurssive_shuffle some_array
> >>    n = some_array.length
> >>    helper_array = []
> >>    new_array = []
> >>    while n != 0
> >>      r = rand(n)
> >>      while some_array.length != (r + 1)
> >>        helper_array.push some_array.pop
> >>        puts 'Array'
> >>        puts helper_array
> >>        puts
> >>      end
> >>      new_array.push some_array.pop
> >>      n = (n - 1)
> >>      helper_array.each do |item|
> >>        some_array.push item
> >>      end
> >>    end
> >>    puts new_array
> >> end
>
> >> shuffle some_array
>
> >> ---------------------------------------------------------------|
> >> ~Ari
> >> "I don't suffer from insanity. I enjoy every minute of it" --1337est
> >> man alive
>
> ---------------------------------------------------------------|
> ~Ari
> "I don't suffer from insanity. I enjoy every minute of it" --1337est
> man alive