From: Phrogz <phrogz@...>
Date: 2007-08-22T01:14:57+09:00
Subject: Re: Detecting duplicates in an array, anything in the standa

On Aug 21, 10:04 am, Ari Brown <a...@aribrown.com> wrote:
> On Aug 21, 2007, at 4:59 AM, Pe�a, Botp wrote:
>
> > From: Robert Klemme [mailto:shortcut...@googlemail.com]
> > # irb(main):002:0> a.uniq.select{|e| (a-[e]).size < a.size - 1}
>
> > compare also,
>
> > irb(main):056:0> b=a.dup
> > => [1, 1, 2, 2, 2, 4, 3]
> > irb(main):057:0> b.uniq.select{|e| (b.reject!{|f| f == e}).size > 1}
> > => [1, 2]
>
> I still think it's easier just to union itself...
>
> a = [1,2,3,2,1]
> b = a & a
> b = [1,2,3]

...but that's not what the OP wanted. What you've written is the same
as the #uniq method.

Don't feel bad, this thread has been filled with people answering the
wrong question. :p The original question was roughly "How do I find
out all the elements in the array that are duplicates?"

Solutions to that question would not include '3' in the above results.
It's unclear to me if %w| a b b b | should include 'b' once or twice
in the output, though, and the original poster has not clarified that,
that I can see.