From: Relm <relm@3tlk.net>
Date: 2005-10-17T18:06:19+09:00
Subject: Re: How to get non-unique elements from an array?

On Sun, 16 Oct 2005, Sam Kong wrote:

> I need to get non-unique elements from an array.
> The best I came up with was using a hash as a counter for each unique
> elements.
> 
> a = [0,1,2,3,4,5,2,3]
> 
> #What I want to get is [2,3] as 2,3 are non-unique elements.

Two variants using regular expressions:

  eval(a.inspect.gsub(/\b(\d+),(?!.*\b\1\b)/,'')).uniq

  a.sort.inspect.scan(/\b(\d+)(, \1\b)+/).map{|x|x[0].to_i}

-- 
Relm