Intersection Filter

intersection_filter.rb

require "minitest/autorun"

class TestIntersectionFilter < Minitest::Test
  def test_data
    [[1, 2, 3], [1, 2, 4], [1, 2, 5],
     [1, 5, 7], [1, 5, 8], [1, 5, 9]]
  end

  def test_that_it_works
    filtered_data = IntersectionFilter.filter(test_data)

    assert_equal [[1, 2, 3], [1, 5, 7]], filtered_data
  end
end

module IntersectionFilter
  def self.filter(test_data, max = 2)
    test_data.reduce([]) { |filtered, to_check|
      filtered.any? { |set| (set & to_check).size >= max } ?
        filtered : filtered + [to_check]
    }
  end
end