Solution to Ruby Koans Scoring Project (about_scoring_project.rb)

about_scoring_project.rb

def counts_from_dice(dice)
  dice.inject({}) do |hash, value|
    hash[value] ||= 0
    hash[value] += 1
    hash
  end
end

def score(dice)
  counts_from_dice(dice).inject(0) do |sum, (number, count)|    
    if count >= 3
      sum += (number == 1 ? 1000 : number * 100)
      extras_count = count - 3
    else
      extras_count = count
    end    

    case number
    when 1
      sum += 100*extras_count
    when 5
      sum += 50*extras_count
    else
      sum += 0
    end
    
    sum
  end
end