「オフラインリアルタイムどう書く第27回(分岐と行き止まり)」の問題を解いてみた

横浜へなちょこプログラミング勉強会にて過去に出題された分岐と行き止まりを解いてみた。
回答にかかった時間は15分程度。
時間配分としては全ルートを書き出すのに10分、コードを書くのに5分。

スタートからゴールまでに通る部分さえ分かってしまえば、通行禁止の線路が含まれていないルートを抽出するだけの力業である。
今回はルート数が少ないので特に工夫もしていないが、これがルート数が膨大な数になるならばもっと工夫しなけれならないだろう。

class Rail
  def initialize
    @routes = {
      1 => [
        {route: [?a, ?b, ?c],     goal: 4},
        {route: [?g, ?c],         goal: 4},
        {route: [?g, ?h],         goal: 4},
        {route: [?a, ?b],         goal: 5},
        {route: [?g, ?e],         goal: 5},
        {route: [?a, ?b, ?c],     goal: 6},
        {route: [?g, ?c],         goal: 6},
        {route: [?g, ?h, ?i],     goal: 6}
      ],
      2 => [
        {route: [?d, ?c],         goal: 4},
        {route: [?h],             goal: 4},
        {route: [?d, ?e],         goal: 5},
        {route: [?d, ?c],         goal: 6},
        {route: [?h, ?i],         goal: 6}
      ],
      3 => [
        {route: [?b, ?c],         goal: 4},
        {route: [?f, ?g, ?c],     goal: 4},
        {route: [?f, ?g, ?h],     goal: 4},
        {route: [?b],             goal: 5},
        {route: [?f, ?g, ?e],     goal: 5},
        {route: [?b, ?c],         goal: 6},
        {route: [?f, ?g, ?c],     goal: 6},
        {route: [?f, ?g, ?h, ?i], goal: 6}
      ]
    }
  end

  def go input
    chars = input.chars
    can = @routes.each_with_object([]){|(start, routes), r|
      routes.each{|route|
        r << "#{start}#{route[:goal]}" unless chars.any?{|c| route[:route].include?(c)}
      }
    }.uniq.sort
    can.empty? ? "-" : can.join(",")
  end
end
test = <<_TEST
/*0*/ test( "befi", "14,16,24,26" );    
/*1*/ test( "abc", "14,15,16,24,25,26,34,35,36" );    
/*2*/ test( "de", "14,15,16,24,26,34,35,36" );    
/*3*/ test( "fghi", "14,15,16,24,25,26,34,35,36" );    
/*4*/ test( "abcdefghi", "-" );    
/*5*/ test( "ag", "24,25,26,34,35,36" );    
/*6*/ test( "dh", "14,15,16,34,35,36" );    
/*7*/ test( "bf", "14,15,16,24,25,26" );    
/*8*/ test( "ch", "15,25,35" );    
/*9*/ test( "be", "14,16,24,26,34,36" );    
/*10*/ test( "ci", "14,15,24,25,34,35" );    
/*11*/ test( "cgi", "15,24,25,35" );    
/*12*/ test( "acgi", "24,25,35" );    
/*13*/ test( "cdefghi", "15,35" );    
/*14*/ test( "acdefghi", "35" );    
/*15*/ test( "cdegi", "15,24,35" );    
/*16*/ test( "bcdegi", "24" );    
/*17*/ test( "afh", "14,15,16,24,25,26,34,35,36" );    
/*18*/ test( "abfh", "14,15,16,24,25,26" );    
/*19*/ test( "dfh", "14,15,16,34,35,36" );    
/*20*/ test( "cdfh", "15,35" );    
/*21*/ test( "deh", "14,15,16,34,35,36" );    
/*22*/ test( "cdeh", "15,35" );    
/*23*/ test( "abefgh", "24,26" );    
/*24*/ test( "abdefgh", "-" );    
/*25*/ test( "acfghi", "25,35" );    
/*26*/ test( "acdfghi", "35" );    
/*27*/ test( "cegi", "15,24,35" );    
/*28*/ test( "abcfhi", "15,25" );    
/*29*/ test( "abcefhi", "-" );    
/*30*/ test( "abdi", "14,15,16,24,34,35,36" );    
/*31*/ test( "abdfi", "14,15,16,24" );    
/*32*/ test( "bdi", "14,15,16,24,34,35,36" );    
/*33*/ test( "bdfi", "14,15,16,24" );    
/*34*/ test( "adfh", "14,15,16,34,35,36" );    
/*35*/ test( "adfgh", "34,35,36" );    
/*36*/ test( "acdfhi", "15,35" );    
/*37*/ test( "bcdfgi", "24" );    
/*38*/ test( "bcdfghi", "-" );    
/*39*/ test( "defi", "14,15,16,24,34,35,36" );    
/*40*/ test( "defhi", "14,15,16,34,35,36" );    
/*41*/ test( "cdefg", "15,24,26,35" );    
/*42*/ test( "cdefgi", "15,24,35" );    
/*43*/ test( "bdefg", "24,26" );    
/*44*/ test( "bdefgi", "24" );
_TEST

require 'minitest/autorun'

describe 'Rail' do
  rail = Rail.new
  test.split("\n").each do |line|
    t, n, input, expect = line.match(/^\/\*(\d+)\*\/\s*test\(\s*"([^"]+)",\s*"([^"]+)"\s*\);*\s*$/).to_a
    it input do
      assert_equal expect, rail.go(input)
    end
  end
end