bowling3.rb

def strike?(pins, idx)
  pins[idx * 2] == 10
end

def spare?(pins, idx)
  pins[idx * 2] + pins[idx * 2 + 1] == 10
end

def score_strike_spare(pins)
  score = 0
  games = [(pins.size + 1) / 2 - 1, 9].min
  games.times do |i|
    next_idx = (i + 1) * 2
    if strike?(pins, i)
      score += pins[next_idx]
      score += pins[next_idx + 1].to_i > 0 ? pins[next_idx + 1] : pins[next_idx + 2].to_i
    elsif spare?(pins, i)
      score += pins[next_idx]
    end
  end
  score
end

def score(pins)
  pins.inject(&:+) + score_strike_spare(pins)
end

def bowl(n)
  @pins ||= []
  @pins << n
  score(@pins)
end

pins = [1, 4, 2, 8, 5, 0, 10, 0, 0, 4, 5, 5, 2, 0, 6, 1, 10, 0, 10, 5, 5]
pins.each do |n|
  puts sprintf("%2d %d\n", n, bowl(n))
end