2019/3/script.rb

#!/usr/bin/env ruby

require_relative '../common'

class Path
  attr_reader :path

  def initialize(path)
    @path = path.split(',')
    @x = @y = 0
  end

  def coordinates
    @coordinates ||= path.inject([]) do |result, move|
      direction = move[0]
      count = move[1..].to_i
      result + count.times.map { |i| move(direction) }
    end
  end

  def move(direction)
    if direction == "L"
      @x -= 1
    elsif direction == "R"
      @x += 1
    elsif direction == "D"
      @y += 1
    elsif direction == "U"
      @y -= 1
    end

    [@x, @y]
  end
end

def part1(path1, path2)
  (path1 & path2).map { |coordinates| coordinates.map(&:abs).sum }.min
end

def part2(path1, path2)
  (path1 & path2).map { |coordinates| path1.index(coordinates) + path2.index(coordinates) + 2 }.min
end

path1, path2 = Input.new(__dir__).readlines.map { |line| Path.new(line).coordinates }

puts "=== Part 1 ==="
puts part1(path1, path2)
puts "=== Part 2 ==="
puts part2(path1, path2)