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def modes(array, find_all=true)
histogram = array.inject(Hash.new(0)) { |h, n| h[n] += 1; h }
modes = nil
histogram.each_pair do |item, times|
modes << item if modes && times == modes[0] and find_all
modes = [times, item] if (!modes && times>1) or (modes && times>modes[0])
end
return modes ? modes[1...modes.size] : modes
end
puts modes([1,2,3,4]) # => nil
puts modes([1,1,2,3,4]) # => [1]
puts modes([1,1,2,2,3,4]) # => [1, 2]
puts modes([1,1,2,2,3,4,4]) # => [1, 2, 4]
puts modes([1,1,2,2,3,4,4], false) # => [1]
puts modes([1,1,2,2,3,4,4,4,4,4]) # => [4]
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