From: "Jan E." <lists@...>
Date: 2012-04-20T08:03:36+09:00
Subject: Re: finding duplicates in an array and its index number

Jan E. wrote in post #1057484:
> A more efficient lowlevel solution would be to iterate over the array,
> compare the values and save the indices in case of duplicates.

... like this:

####
x = [1, 2, 3, 2, 4, 5, 4, 4]

duplicates = {}
x.each_with_index do |value, i|
  (i + 1).upto x.length - 1 do |j|
    if x[j] == value
      duplicates[value] = [i] if duplicates[value].nil?
      duplicates[value] << j
      break
    end
  end
end

p duplicates
####

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