Advent of Code, day 6

day6.rb

#!/usr/bin/env ruby

# http://adventofcode.com/day/6

class Lights

  def initialize
    @lights = HEIGHT.times.map do
      [false] * WIDTH
    end
  end

  def change(x1, y1, x2, y2, &block)
    (x1..x2).each do |x|
      (y1..y2).each do |y|
        @lights[x][y] = yield(@lights[x][y])
      end
    end
  end

  def num_lit
    @lights.flatten.count(&:itself)
  end

  private

  WIDTH = HEIGHT = 1000
  
end

COMMANDS = {
  "turn on" => ->(on) { true },
  "turn off" => ->(on) { false },
  "toggle" => ->(on) { !on },
}

lights = Lights.new
File.open("input", "r") do |file|
  file.each_line do |line|
    raise unless line =~ /^(.*) (\d+),(\d+) through (\d+),(\d+)$/
    command, x1, y1, x2, y2 = $~.captures
    x1 = Integer(x1)
    y1 = Integer(y1)
    x2 = Integer(x2)
    y2 = Integer(y2)
    lights.change(x1, y1, x2, y2, &COMMANDS.fetch(command))
  end
end
puts lights.num_lit

day6_part2.rb

#!/usr/bin/env ruby

# http://adventofcode.com/day/6

class Lights

  def initialize
    @lights = HEIGHT.times.map do
      [0] * WIDTH
    end
  end

  def change(x1, y1, x2, y2, &block)
    (x1..x2).each do |x|
      (y1..y2).each do |y|
        @lights[x][y] = yield(@lights[x][y])
      end
    end
  end

  def total_brightness
    @lights.flatten.reduce(&:+)
  end

  private

  WIDTH = HEIGHT = 1000
  
end

COMMANDS = {
  "turn on" => ->(brightness) { brightness + 1 },
  "turn off" => ->(brightness) { [brightness - 1, 0].max },
  "toggle" => ->(brightness) { brightness + 2 },
}

lights = Lights.new
File.open("input", "r") do |file|
  file.each_line do |line|
    raise unless line =~ /^(.*) (\d+),(\d+) through (\d+),(\d+)$/
    command, x1, y1, x2, y2 = $~.captures
    x1 = Integer(x1)
    y1 = Integer(y1)
    x2 = Integer(x2)
    y2 = Integer(y2)
    lights.change(x1, y1, x2, y2, &COMMANDS.fetch(command))
  end
end
puts lights.total_brightness