Ruby difference in array including duplicates

Question

[1,2,3,3] - [1,2,3] produces the empty array []. Is it possible to retain duplicates so it returns [3]?

Answer 1

As far as I know, you can't do this with a built-in operation. Can't see anything in the ruby docs either. Simplest way to do this would be to extend the array class like this:

class Array
    def difference(array2)
        final_array = []
        self.each do |item|
            if array2.include?(item)
                array2.delete_at(array2.find_index(item))
            else
                final_array << item
            end
        end
    end
end

For all I know there's a more efficient way to do this, also