1  
   2  class Array
   3    def real_intersection(arr2)
   4      self_sorted = self.sort
   5      target_sorted = arr2.sort
   6      intersection= []
   7      jstart=0
   8      for i in (0..self_sorted.length-1)
   9        for j in (jstart..target_sorted.length-1)
  10          if self_sorted[i] == target_sorted[j]
  11            jstart = j+1
  12            intersection[intersection.length] = self_sorted[i]
  13            break
  14          end
  15        end
  16      end
  17      return intersection
  18    end
  19  end

   1  
   2  require 'test/unit'
   3  
   4  class ArrayIntersectionTests < Test::Unit::TestCase    
   5    def test_real_array_intersection
   6      assert_equal [2], [2, 2, 2, 3, 7, 13, 49] & [2, 2, 2, 5, 11, 107]
   7      assert_equal [2, 2, 2], [2, 2, 2, 3, 7, 13, 49].real_intersection([2, 2, 2, 5, 11, 107])
   8      assert_equal ['a', 'c'], ['a', 'b', 'a', 'c'] & ['a', 'c', 'a', 'd']
   9      assert_equal ['a', 'a', 'c'], ['a', 'b', 'a', 'c'].real_intersection(['a', 'c', 'a', 'd'])
  10    end
  11  end