my submission for http://rubylearning.com/blog/2010/07/31/rpcfn-cycle-tracks-12/

skip_tracks.rb

# my submission for http://rubylearning.com/blog/2010/07/31/rpcfn-cycle-tracks-12/
#
# update: I hadn't realized it, but this challenge actually ended today. 
# Mine was very similar to the guy who won, which you can see at http://gist.github.com/502083
# (though he included a very nice 1.9 only solution)

def skip_tracks( ary , i )
  i %= ary.size
  ary.replace  ary[i..-1]+ary[0...i]
end



require 'test/unit'
class SkipTracksTester < Test::Unit::TestCase
  def setup
    @playlist = (0..4).to_a.map { |tracknumber| tracknumber.to_s }
  end
  def test_negative_15()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , -15 )  end
  def test_negative_14()  assert_equal ["1", "2", "3", "4", "0"]  ,  skip_tracks( @playlist , -14 )  end
  def test_negative_13()  assert_equal ["2", "3", "4", "0", "1"]  ,  skip_tracks( @playlist , -13 )  end
  def test_negative_12()  assert_equal ["3", "4", "0", "1", "2"]  ,  skip_tracks( @playlist , -12 )  end
  def test_negative_11()  assert_equal ["4", "0", "1", "2", "3"]  ,  skip_tracks( @playlist , -11 )  end
  def test_negative_10()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , -10 )  end
  def test_negative_15()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , -15 )  end
  def test_negative__9()  assert_equal ["1", "2", "3", "4", "0"]  ,  skip_tracks( @playlist , -9  )  end
  def test_negative__8()  assert_equal ["2", "3", "4", "0", "1"]  ,  skip_tracks( @playlist , -8  )  end
  def test_negative__7()  assert_equal ["3", "4", "0", "1", "2"]  ,  skip_tracks( @playlist , -7  )  end
  def test_negative__6()  assert_equal ["4", "0", "1", "2", "3"]  ,  skip_tracks( @playlist , -6  )  end
  def test_negative__5()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , -5  )  end
  def test_negative__4()  assert_equal ["1", "2", "3", "4", "0"]  ,  skip_tracks( @playlist , -4  )  end
  def test_negative__3()  assert_equal ["2", "3", "4", "0", "1"]  ,  skip_tracks( @playlist , -3  )  end
  def test_negative__2()  assert_equal ["3", "4", "0", "1", "2"]  ,  skip_tracks( @playlist , -2  )  end
  def test_negative__1()  assert_equal ["4", "0", "1", "2", "3"]  ,  skip_tracks( @playlist , -1  )  end
  def test_positive__0()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , 0   )  end
  def test_positive__1()  assert_equal ["1", "2", "3", "4", "0"]  ,  skip_tracks( @playlist , 1   )  end
  def test_positive__2()  assert_equal ["2", "3", "4", "0", "1"]  ,  skip_tracks( @playlist , 2   )  end
  def test_positive__3()  assert_equal ["3", "4", "0", "1", "2"]  ,  skip_tracks( @playlist , 3   )  end
  def test_positive__4()  assert_equal ["4", "0", "1", "2", "3"]  ,  skip_tracks( @playlist , 4   )  end
  def test_positive__5()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , 5   )  end
  def test_positive__6()  assert_equal ["1", "2", "3", "4", "0"]  ,  skip_tracks( @playlist , 6   )  end
  def test_positive__7()  assert_equal ["2", "3", "4", "0", "1"]  ,  skip_tracks( @playlist , 7   )  end
  def test_positive__8()  assert_equal ["3", "4", "0", "1", "2"]  ,  skip_tracks( @playlist , 8   )  end
  def test_positive__9()  assert_equal ["4", "0", "1", "2", "3"]  ,  skip_tracks( @playlist , 9   )  end
  def test_positive_10()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , 10  )  end
  def test_positive_11()  assert_equal ["1", "2", "3", "4", "0"]  ,  skip_tracks( @playlist , 11  )  end
  def test_positive_12()  assert_equal ["2", "3", "4", "0", "1"]  ,  skip_tracks( @playlist , 12  )  end
  def test_positive_13()  assert_equal ["3", "4", "0", "1", "2"]  ,  skip_tracks( @playlist , 13  )  end
  def test_positive_14()  assert_equal ["4", "0", "1", "2", "3"]  ,  skip_tracks( @playlist , 14  )  end
  def test_positive_15()  assert_equal ["0", "1", "2", "3", "4"]  ,  skip_tracks( @playlist , 15  )  end
end