archaeology_solution.rb

require 'benchmark'

#CHALLENGE:
#Please write a paragraph explaining what it does and how it works. Then, rewrite it so that it's
#beautiful and elegant and the intent is clear. Feel free to use any references or tools you would
#normally use.

def function(a)	
  a.inject({}){ |a,b| a[b] = a[b].to_i + 1; a}.reject{ |a,b| b == 1 }.keys
end

puts "Original method:"
puts function([0, 1, 1, 2, 2, 3])

#Upon second look (and a nudge in the right direction from Robert)
#the code appears to return any elements that appear more than once.
#The inject block returns a hash with each element and the corresponding
#number of times that the element appears in the array.
#The reject block returns any element that has a value of more than one

#This is how I would do it:

def duplicated_elements_in(array)
  array.select{ |element| array.count(element) > 1 }.uniq
end

#Despite the increased expressiveness, this method is shorter

puts"New method:"
puts duplicated_elements_in([4,8,8,15,23,42,42,42])

puts "Let's benchmark the methods for performance:"

array = [0, 1, 1, 2, 2, 3]

Benchmark.bmbm(7) do |bm|
  bm.report('old method') do
    function(array)
  end

  bm.report('new method') do
    duplicated_elements_in(array)
  end
end

#And my version is (slightly) faster.