From: Simon Strandgaard <neoneye@...>
Date: 2005-10-18T03:15:46+09:00
Subject: Re: How to get non-unique elements from an array?

On 10/17/05, Ryan Leavengood <leavengood@gmail.com> wrote:
> On 10/17/05, Simon Strandgaard <neoneye@gmail.com> wrote:
> > On 10/17/05, pauldacus@gmail.com <pauldacus@gmail.com> wrote:
> > > Young grasshoppers... let us never forget the power of the REGEX!  Let
> > > us not bother with counters or blocks... let us GSUB this bad boy!
> > >
> > > a = [0,1,2,3,4,5,2,3]
> > >
> > > a.sort.to_s.gsub(/(.)(\1)+/, '').split(//)
> > >
> > > =>["0", "1", "4", "5"]
> >
> >
> > no need to sort.. :-)
> >
> > a = [0, 1, 2, 3, 4, 5, 2, 3]
> > a.to_s.delete(a.to_s.gsub(/(.)(?!.*\1)/,'')).split('').map{|i|i.to_i}
> > #=> [0, 1, 4, 5]
>
> Both are interesting solutions, but you are returning the unique
> elements of the array, not the non-unique ones, which was the original
> problem. I say this not to be pedantic, but to see how you would solve
> it.

Sorry should be without the delete..

a = [0, 1, 2, 3, 4, 5, 2, 3]
a.to_s.gsub(/(.)(?!.*\1)/,'').split('').map{|i|i.to_i}
#=> [2, 3]

--
Simon Strandgaard