From: Karsten Meier <developer@...>
Date: 2012-01-23T19:15:52+09:00
Subject: Re: uniq with count; better way?

If your data items are integers, and from a rather small range (compared 
to computer memory...), then you can use an array instead of an hash:

maxval = 10
result = Array.new(maxval+1, 0)
ar.each{
  |x| result[x] += 1;
}

This returns an array and not an hash.
[0, 0, 0, 0, 2, 2, 3, 1, 0, 0, 0]

To make a histogram, that data structure is even better. Otherwise you 
need to transform it to a hash again. But for large data sets I still 
expect it  to be faster:
Your cpu  does not need to calculate a hash key of every single data 
item, because the data item is already a perfect key for the array. Also 
no hash key collisions can occur.


Regards

Karsten Meier

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