From: Jimmy Kofler <koflerjim@...>
Date: 2007-08-22T04:42:07+09:00
Subject: Re: Detecting duplicates in an array, anything in the standa

> Jeremy Woertink wrote:
> I actually had to ... find all the duplicate account 
> numbers and the number of times they were duplicated and ... .
> ...
> ~Jeremy


A much less verbose 'nil' fix of the original version would be to use 
[v] instead of v:

a = [nil,1,2,2,3,nil]
p a.uniq.map {|v| (a - [v]).size < (a.size - 1) ? [v] : 
nil}.compact.flatten
=> [nil, 2]


And with this fixed version it's also possible to count & grab duplicate 
array items in one go:

a = [nil,1,2,2,3,nil,nil]
a = (a * 5 << "unique_obj1" << "unique_obj2").sort_by { rand }

p a.uniq.map {|v| diff = (a.size - (a-[v]).size); (diff > 1) ? [v, diff] 
: nil}.compact

=> [[2, 10], [3, 5], [nil, 15], [1, 5]]


Cheers,

j.k.
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