About Scoring from Ruby Koans

about_scoring_project.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 to 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.

def score(dice)
  score = 0
  return score if dice.empty?
  counts = [0,0,0,0,0,0]
  dice.each {|d| counts[d-1] += 1 }
  
  ones, twos, threes, fours, fives, sixes = counts

  if ones >= 3 then
    score += 1000 + ((ones-3) * 100)
  else
    score += (ones * 100)
  end 

  if fives >= 3 then
    score += 500 + ((fives-3) * 50)
  else
    score += fives * 50
  end 
  
  score += 200 if twos >= 3
  score += 300 if threes >= 3
  score += 400 if fours >= 3  
  score += 600 if sixes >= 3
  
  score
end

class AboutScoringProject < EdgeCase::Koan
  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_mixed_is_sum
    assert_equal 250, score([2,5,2,2,3])
    assert_equal 550, score([5,5,5,5])
  end

end

here was my take on this.
But I didnt refactor it after the comment left by Corey. I will soon have time again to dig more into ruby :)
https://gist.github.com/906429

Interesting approach ...

Most of the solutions I have seen to this, including yours, uses multiple enumerations - I think I count 4 in yours - in mine I made a conscious choice to eliminate looping over anything more than the once necessary to count the elements

Not sure if my approach is less "Rubyish" because of that

I also made a conscious effort to keep my algorithm close to the definition of the problem - so for example, I explicit use "1000" as the score for 3 ones, and add the extras on above that (where as your solution, and many others I have seen, pre-calculates the sum for 3, minus the figure for each.