From: Robert Klemme <shortcutter@...>
Date: 2007-08-20T22:50:28+09:00
Subject: Re: Detecting duplicates in an array, anything in the standard library ?

2007/8/20, thomas.macklin@gmail.com <thomas.macklin@gmail.com>:
> 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.

It does, but as far as I can see OP wanted exactly the duplicates back.

Cheers

robert