02-2.rb

#!/usr/bin/env ruby

lines = File.read('02.input').lines.map(&:strip)

line_format = /^Game (?<num>[[:digit:]]+): (?<reveals>.*)$/

games = {}

lines.each do |line|
  m = line.match line_format
  games[m['num'].to_i] = []
  reveals = m['reveals'].split ';'
  reveals.each do |reveal|
    colours = {
      'red' => 0,
      'green' => 0,
      'blue' => 0
    }
    tokens = reveal.delete(',').split
    until tokens.empty?
      num = tokens.shift.to_i
      colour = tokens.shift
      colours[colour] = num
    end
    games[m['num'].to_i] << colours
  end
end

def power(game)
  required = {
    'red' => 0,
    'green' => 0,
    'blue' => 0
  }
  game.each do |reveal|
    ['red', 'green', 'blue'].each do |colour|
      required[colour] = [required[colour], reveal[colour]].max
    end
  end
  required['red'] * required['green'] * required['blue']
end

print games.values.map { |g| power(g) }.sum, "\n"