From: Sam Kong <sam.s.kong@...>
Date: 2005-10-16T04:11:55+09:00
Subject: Re: How to get non-unique elements from an array?

> You don't need the exact number of repetitions. Try this:
> a = [0,1,2,3,4,5,2,3]
> h = {}
> u = a.inject([]) {|res, x| h[x] ? res + [x] : h[x] = res}

Thank you for the insight.

However, your code doesn't work if an element repeats more than twice.

a = [0,1,2,3,4,5,2,3,2] #there are three 2's.
Your code's result is [2, 3, 2] instead of [2, 3]
It should be modified like
u = a.inject([]) {|res, x| h[x] ? res + [x] : h[x] = res}.uniq

Other than that, I like your way.
Thank you again.

Sam