From: "David A. Black" <dblack@...>
Date: 2007-08-21T20:49:15+09:00
Subject: Re: Detecting duplicates in an array, anything in the standa

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Hi --

On Tue, 21 Aug 2007, Ryan Davis wrote:

>
> On Aug 21, 2007, at 01:59 , Pe=F1a, Botp wrote:
>
>> From: Robert Klemme [mailto:shortcutter@googlemail.com]
>> # irb(main):002:0> a.uniq.select{|e| (a-[e]).size < a.size - 1}
>>=20
>> compare also,
>>=20
>> irb(main):056:0> b=3Da.dup
>> =3D> [1, 1, 2, 2, 2, 4, 3]
>> irb(main):057:0> b.uniq.select{|e| (b.reject!{|f| f =3D=3D e}).size > 1}
>> =3D> [1, 2]
>
> I came up with something vaguely similar:
>
> class Array
>  def dupes
>    a =3D self.dup
>    self.partition { |o| a.delete(o) }.last
>  end
> end
>
>>> [1,2,2,3,4,4].dupes
> =3D> [2, 4]

You'd want to throw a .uniq on there; otherwise, non-consecutive dupes
get processed twice:

>> [1,2,2,3,4,4,2].dupes
=3D> [2, 4, 2]


David

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