scoring_take2.rb

require File.expand_path(File.dirname(__FILE__) + '/edgecase')

# Greed is a dice game where you roll up to five dice to accumulate
# points.  The following "score" function will be used calculate the
# score of a single roll of the dice.
#
# A greed roll is scored as follows:
#
# * A set of three ones is 1000 points
#   
# * A set of three numbers (other than ones) is worth 100 times the
#   number. (e.g. three fives is 500 points).
#
# * A one (that is not part of a set of three) is worth 100 points.
#
# * A five (that is not part of a set of three) is worth 50 points.
#
# * Everything else is worth 0 points.
#
#
# Examples:
#
# score([1,1,1,5,1]) => 1150 points
# score([2,3,4,6,2]) => 0 points
# score([3,4,5,3,3]) => 350 points
# score([1,5,1,2,4]) => 250 points
#
# More scoring examples are given in the tests below:
#
# Your goal is to write the score method.


class AboutScoringAssignment < EdgeCase::Koan


  class ::Integer
    def score_for_single
      if self == 1 
        100
      elsif self ==5 
        50
      else
        0
      end
    end

    def score_for_triple
      if self == 1 
        1000
      else
        self * 100
      end
    end
  end
  
  State = Struct.new(:last_value)

  def returning(value) yield; value; end
  
  def score(input)    
    slices = input.sort.slice_before(State.new(input.first)) {|value, state|
      returning(value != state.last_value) {state.last_value = value}}
    
    slices.inject(0) {|total, slice| total + score_for_number(slice, slice.first)}
  end
      
  def score_for_number(selected, num)    
    if selected.size >= 3
       (num.score_for_triple + (num.score_for_single * (selected.size - 3))) 
    else 
        (num.score_for_single * selected.size)      
    end
  end
  
  def test_score_of_an_empty_list_is_zero
    assert_equal 0, score([])
  end

  def test_score_of_a_single_roll_of_5_is_50
    assert_equal 50, score([5])
  end

  def test_score_of_a_single_roll_of_1_is_100
    assert_equal 100, score([1])
  end

  def test_score_of_multiple_1s_and_5s_is_the_sum_of_individual_scores
    assert_equal 300, score([1,5,5,1])
  end

  def test_score_of_single_2s_3s_4s_and_6s_are_zero
    assert_equal 0, score([2,3,4,6])
  end

  def test_score_of_a_triple_1_is_1000
    assert_equal 1000, score([1,1,1])
  end

  def test_score_of_other_triples_is_100x
    assert_equal 200, score([2,2,2])
    assert_equal 300, score([3,3,3])
    assert_equal 400, score([4,4,4])
    assert_equal 500, score([5,5,5])
    assert_equal 600, score([6,6,6])
  end

  def test_score_of_more_than_triple_others_is_still_100x
    assert_equal 200, score([2,2,2,2])
    assert_equal 300, score([3,3,3,3,3])
    assert_equal 400, score([4,4,4,4])
    assert_equal 600, score([6,6,6,6])
  end

  def test_score_of_mixed_is_sum
    assert_equal 250, score([2,5,2,2,3])
    assert_equal 550, score([5,5,5,5])
    assert_equal 1100, score([1,1,1,1])
  end
end

For comparison's sake, see my earlier attempt: http://gist.github.com/573169 and @youngnh's take: http://gist.github.com/573769