From: Sean O'Halpin <sean.ohalpin@...>
Date: 2007-10-29T03:47:28+09:00
Subject: Re: Duplicate elements in array

On 10/28/07, Mohit Sindhwani <mo_mail@onghu.com> wrote:
>
> Thanks Sean!  Makes me feel quite nice about it.
>
> So, hashes are faster than arrays?
>
> Cheers,
> Mohit.
> 10/29/2007 | 2:13 AM.

It depends what you're doing with them and how big they are. But in
this instance, I changed your solution to use a hash because you were
appending the duplicates to an array which resulted in adding an entry
to that array every time you detected a duplicate. This didn't show up
in your example because your data contained at most two instances of
an item. If you change your example to:

array = ["apple", "banana", "apple", "orange", "fat", "cow", "cow",
"apple", "apple"]
h = Hash.new
duplicates = []

array.each {|item|
   if h.has_key?(item) then
       duplicates << item
   else
       h[item] = 0 #it doesn't matter what we store
   end
}

puts duplicates

it outputs

apple
cow
apple
apple

which is probably not what you want.

Regards,
Sean