hidenba.rb

class Point
  attr_accessor :point, :color

  def initialize(point, color)
    @point = point
    @color = color
  end

  def toggle
    @color = color == 'R' ? 'W' : 'R'
  end
end

class Star
  attr_reader :points

  LINES = %w(AJIC AFGD BJFE BIHD CHGE)

  def initialize
    @points = {'A': Point.new('A', 'W'),
               'B': Point.new('B', 'W'),
               'C': Point.new('C', 'W'),
               'D': Point.new('D', 'W'),
               'E': Point.new('E', 'W'),
               'F': Point.new('F', 'R'),
               'G': Point.new('G', 'R'),
               'H': Point.new('H', 'R'),
               'I': Point.new('I', 'R'),
               'J': Point.new('J', 'R')
              }
  end

  def trace(route)
    routes = route.split(//)

    routes.each do |point|
      base = points[point.to_sym]
      base.toggle

      LINES.each do |line|
        base_index = line.index(base.point)

        if base_index
          if base_index >= 2
            base_index = line.reverse.index(base.point)
            traces = line.reverse.split(//).map { |key| points[key.to_sym]}
          else
            traces = line.split(//).map { |key| points[key.to_sym]}
          end

          if !traces[base_index+2].nil? && traces[base_index+2].color == base.color && traces[base_index+1].color != base.color
            traces[base_index+1].toggle
          elsif !traces[base_index+3].nil? && traces[base_index+3].color == base.color && traces[base_index+1].color != base.color && traces[base_index+2].color != base.color
            traces[base_index+1].toggle
            traces[base_index+2].toggle
          end
        end
      end
    end

    points.map { |_k, v| v.color }.join('')
  end
end

def test(route, result)
  traced = Star.new.trace(route)
  puts "#{traced}: #{traced == result}"
end

test("A", "RWWWWRRRRR")
test("F", "WWWWWWWRRW")
test("J", "WWWWWWRRWW")
test("AA", "WWWWWWWRWW")
test("IC", "WWRWWRRRWW")
test("FC", "WWRWWWWRRW")
test("AE", "RWWWRRRRRR")
test("GJ", "WWWWWWWWWW")
test("CCB", "WRWWWRWWWR")
test("BEF", "WRWWRWWRRR")
test("JGD", "WWWRWWWWWW")
test("IHCC", "WWWWWRWWWW")
test("AIDD", "RWWWWRRWWR")
test("IJFA", "RWWWWWWWWW")
test("ABCDE", "RRRRRRRRRR")
test("ICEBA", "RRRWRRRRRR")
test("DAHHD", "RWWWWRWWWR")
test("GJIJC", "WWRWWWWWRR")
test("FGHIJ", "WWWWWWWWRR")
test("HJICGA", "RWRWWRRRRR")
test("IBCIGC", "WRWWWWWWWW")
test("BIJJJB", "WWWWWWRWWW")
test("DCBCHGD", "WRWWWWWRRW")
test("JEABDHD", "RRWWRRRWRR")
test("JHFADHE", "RWWRRRRRWW")
test("HDGGDBIB", "WWWWWWWWWW")
test("IIDIHCCG", "WWWRWRRWWW")
test("BBFBICIE", "WRRWRRRWWW")
test("HJHCFBJGG", "WRRWWWWRRW")
test("AJJIEAAII", "RWWWRWWWWR")
test("AIDHJFGAE", "WWWRRWWWWW")
test("FGBGHCBHJJ", "WWRWWWWRRW")
test("EFIGIGGHHJ", "WWWWRRRWWR")
test("HGAFDIFFFF", "RWWRWRRRRW")
test("AABBCCDDEE", "WWWWWWWWWW")
test("ABCDEFGHIJ", "RRRRRWWWWW")
test("FGHIJABCDE", "RRRRRRRRRR")