ruby koans: about_scoring_project.rb

gistfile1.rb

# 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)
  # You need to write this method
  dict = dice.inject({}) {|dict, n|
    dict[n] = dict.fetch(n, 0) + 1; dict
  }

  three_numbers_point = (1..6).map do |n|
    base = n == 1 ? 10 : n
    if (i = dict.fetch(n, 0) / 3) > 0
      base * 100 * i
    else
      0
    end
  end.reduce(:+)

  one_point  = dict.fetch(1, 0) % 3 * 100
  five_point = dict.fetch(5, 0) % 3 * 50

  three_numbers_point + one_point + five_point
end