From: thomas.macklin@...
Date: 2007-08-20T21:45:01+09:00
Subject: Re: Detecting duplicates in an array, anything in the standard library ?

On Aug 19, 5:16 pm, Robert Klemme <shortcut...@googlemail.com> wrote:
> On 19.08.2007 23:15, Robert Klemme wrote:
>
>
>
> > On 19.08.2007 12:38, Thibaut Barr�re wrote:
> >> Hi!
>
> >> Just wondering if there is something simple already built in the std
> >> library to remove duplicates from an array (or an enumerable). I've
> >> seen and used various approaches, like:
>
> >> module Enumerable
> >>   def dups
> >>     inject({}) {|h,v| h[v]=h[v].to_i+1; h}.reject{|k,v| v==1}.keys
> >>   end
> >> end
>
> >> which will give:
>
> >>> %w(a b c c).dups
> >> => ["c"]
>
> > Actually you are not deleting duplicates as far as I can see.
>
> Did I say it's too late?  Man, I should've worn my glasses...
>
> > Here's another one
>
> > irb(main):012:0> a.inject(Hash.new(0)) {|h,x|
> > h[x]+=1;h}.inject([]){|h,(k,v)|h<<k if v>1;h}
> > => ["c"]
>
> > You could even change that to need just one iteration through the
> > original array but it's too late and I'm too lazy. :-)
>
> Cheers
>
>         robert

or...

require 'set'

new_ary = ary.to_set.to_a #set strips dups.