day6.rb

#!/usr/bin/env ruby

map = {}
xpos = 0
ypos = 0

mech = {
  "turn on" => :turn_on,
  "turn off" => :turn_off,
  "toggle" => :toggle,
}

def turn_on(x)
  # true
  return 1 if x.nil?
  x + 1
end

def turn_off(x)
  # false
  return 0 if x.nil? or x == 0
  x - 1
end

def toggle(x)
  # !x
  return 2 if x.nil?
  x + 2
end

[*0..1000].each { |i| map[i] = {} }

STDIN.each_line do |l|
  l =~ /(turn on|turn off|toggle)\s+(\d+),(\d+) through (\d+),(\d+)/ or raise "couldn't parse: #{l}"
  mech_func = mech[$1]
  [*$2.to_i..$4.to_i].each do |x|
    [*$3.to_i..$5.to_i].each do |y|
      map[x][y] = send mech_func, map[x][y]
    end
  end
end

sum = 0
[*0..1000].each do |x|
  [*0..1000].each do |y|
    sum += map[x][y] if map[x][y]
  end
end
puts sum