Average bowling score

sample.txt

213025x141570447043-
5/630/038/3427725370-
44x07109/x2071016/2
448/418/0270808/818/1
612144x43x6/250/81-
308/039/908/3/318031-
09165026701716146/54-
3/400017314217617/1/0
x7/529060204/8072x1/
71705/9013107161126/x

score.rb

#!/usr/bin/env ruby
#
# scoring:
#     * [0-9]{2} - open frame, add points
#     * [0-9]/   - spare, count next ball's score
#     * x        - strike, count next two balls' scores
#     * -        - no third ball on 10th frame
#
# find the average of all the games, rounded to the nearest hundredth

gameslist = "sample.txt"
# pattern to split line (representing a game) into frames
pattern = /[0-9\/x]{1,2}$|[0-9]{2}|[0-9]\/|x/
score = 0 # running score
game_count = 0 # game counter

File.open(gameslist, "r") do |file|
  while line = file.gets
    current = 0
    # each line is a game
    game_count += 1
    line.scan(pattern).each_with_index do |frame, i|
      # no such thing as 11th frame, only 10th frame bonus
      next if i == 10
                 # spare, add 10 and next ball's points as bonus
        score += if frame[1] == "/"
                        # next ball is a strike, add 10
                   10 + if line[current + 2] == "x"
                          10
                        # next ball wasn't a strike, add next ball's points
                        else
                          line[current + 2].to_i
                        end
                 # strike, add 10 and next 2 balls' points as bonuses
                 elsif frame[0] == "x"
                        # next frame is strike
                   10 + if line[current + 1] == "x"
                               # turkey
                          10 + if line[current + 2] == "x"
                                 10
                               # not a strike, add the points
                               else
                                 line[current + 2].to_i
                               end
                        # next frame is spare, just add 10
                        elsif line[current + 2] == "/"
                          10
                        # next frame is open, add those two balls' points
                        else
                          line[current + 1].to_i + line[current + 2].to_i
                        end
                 # open frame, just add the points
                 else
                   frame[0].to_i + frame[1].to_i
                 end
      current += frame.size
    end
  end
end
puts "Average: #{((score / game_count.to_f) * 100).round / 100.0}"