Advent of Code, Day 2

day2.rb

instructions = File.readlines("input_d2.txt").map(&:chomp!)
x, y = 0, 0

instructions.each do |cmd|
  direction, amt = cmd.match(/(forward|up|down) (\d+)/)[1..-1]
  case direction
  when "forward"
    x += amt.to_i
  when "up"
    y -= amt.to_i
  when "down"
    y += amt.to_i
  end
end

puts "Part 1: #{x * y}"

x, y, aim = 0, 0, 0
instructions.each do |cmd|
  direction, amt = cmd.match(/(forward|up|down) (\d+)/)[1..-1]
  amt = amt.to_i
  case direction
  when "forward"
    x += amt
    y += aim * amt
  when "up"
    aim -= amt
  when "down"
    aim += amt
  end
end
puts "Part 2: #{x * y}"