オフラインリアルタイムどう書くE23 への yancya の回答 http://nabetani.sakura.ne.jp/hena/orde23nokoch/

main.rb

require 'pg'

def main(str)
  n, inputs = str.split(',')
  inputs_sql = inputs.chars.map { |s| "('#{s}')" }.join(', ')

  sql = <<~SQL
  WITH RECURSIVE rules(symbol, "no", angle) AS (
       VALUES('a', 1, 0), ('a', 2, 60), ('a', 3, -60), ('a', 4, 0),
             ('b', 1, 0), ('b', 2, 60), ('b', 3, 0), ('b', 4, -60), ('b', 5, 0))

     , inputs AS (
SELECT ROW_NUMBER() OVER() AS "no"
     , symbol
  FROM (VALUES#{inputs_sql}) AS symbols(symbol))

      , t AS (
 SELECT Array[0] AS no
      , 0 AS angle

 UNION ALL

 SELECT t."no" || rules."no"
      , t.angle + rules.angle
   FROM t
   JOIN inputs ON ARRAY_LENGTH(t."no", 1) = inputs."no"
   JOIN rules ON rules.symbol = inputs.symbol)

  SELECT angle % 360 AS angle
    FROM t
   WHERE ARRAY_LENGTH(t."no", 1) - 1 = #{inputs.size}
ORDER BY t."no"
  OFFSET #{n} - 1
   LIMIT 1
  SQL

  res = PG.connect.exec(sql).first

  return 'x' if res.nil?

  case res['angle']
  when '0', '180', '-180'
    '0'
  when '60', '-300', '-120', '240'
    '+'
  when '-60', '300', '120', '-240'
    '-'
  end
end

require 'test-unit'

class HogeTest < Test::Unit::TestCase
  TEST_CASES = DATA.each_line.map { |line|
    %r[^/\*(?<id>\d+)\*/.*test\((?<act_exp>.*)\)] =~ line
    act, exp = act_exp.scan(%r["(.+?)"]).flatten
    [id, [act, exp]]
  }.to_h

  data(TEST_CASES)
  test "hoge" do |(input, expected)|
    assert { main(input) == expected }
  end
end

__END__
/*0*/ test( "120,aabb", "0" );
/*1*/ test( "100,a", "x" );
/*2*/ test( "3,a", "-" );
/*3*/ test( "3,b", "0" );
/*4*/ test( "9,aa", "-" );
/*5*/ test( "10,bb", "+" );
/*6*/ test( "11,ab", "-" );
/*7*/ test( "12,ba", "0" );
/*8*/ test( "7,aaa", "0" );
/*9*/ test( "17,baa", "+" );
/*10*/ test( "28,bba", "-" );
/*11*/ test( "82,bba", "+" );
/*12*/ test( "35,baa", "-" );
/*13*/ test( "254,babb", "+" );
/*14*/ test( "462,abba", "x" );
/*15*/ test( "226,bbba", "0" );
/*16*/ test( "345,bbba", "0" );
/*17*/ test( "256,aaaa", "0" );
/*18*/ test( "11,aaab", "-" );
/*19*/ test( "241,abaab", "-" );
/*20*/ test( "490,aabaa", "0" );
/*21*/ test( "1305,bbbaa", "0" );
/*22*/ test( "1102,ababa", "-" );
/*23*/ test( "1077,abbab", "-" );
/*24*/ test( "281,aabaa", "-" );
/*25*/ test( "2218,abbaaa", "+" );
/*26*/ test( "4095,bbabbb", "+" );
/*27*/ test( "2750,abbaab", "+" );
/*28*/ test( "5573,bbaaba", "+" );
/*29*/ test( "6644,aaabba", "x" );
/*30*/ test( "8109,bbbbba", "+" );
/*31*/ test( "3860,aaaabbb", "+" );
/*32*/ test( "59222,bbbbbba", "0" );
/*33*/ test( "14956,baabbab", "-" );
/*34*/ test( "14894,ababbba", "+" );
/*35*/ test( "3163,aaaaaab", "-" );
/*36*/ test( "21917,babaaaa", "+" );
/*37*/ test( "178620,aabbbaab", "x" );
/*38*/ test( "96709,babbaaaa", "0" );
/*39*/ test( "74116,abababaa", "-" );
/*40*/ test( "22025,abbbbabb", "0" );
/*41*/ test( "8612,aaaabbaa", "-" );
/*42*/ test( "153868,bbbabbab", "-" );
/*43*/ test( "747769,abbabaaba", "x" );
/*44*/ test( "541589,baabbbbab", "-" );
/*45*/ test( "787443,ababbbbab", "-" );
/*46*/ test( "129549,ababaaaaa", "0" );
/*47*/ test( "837323,aabbbabab", "x" );
/*48*/ test( "140592,bbbbabbab", "+" );
/*49*/ test( "219669,ababbabbab", "-" );
/*50*/ test( "500261,bbababaabb", "-" );
/*51*/ test( "966503,aaabababbb", "0" );
/*52*/ test( "443603,baabaababb", "+" );
/*53*/ test( "3912,aabbababaa", "0" );
/*54*/ test( "2926358,bbabbbbaba", "0" );
/*55*/ test( "18104279,bbbaababbab", "-" );
/*56*/ test( "3849980,aaabaaaaaba", "0" );
/*57*/ test( "9276072,baabaabaaab", "0" );
/*58*/ test( "11202113,baaaaabbbba", "0" );
/*59*/ test( "5432578,abaabbaaaaa", "-" );
/*60*/ test( "17363025,bbaabababbb", "0" );
/*61*/ test( "24147656,baabaabbbbab", "0" );
/*62*/ test( "1078733,bbbaaaabbbbb", "+" );
/*63*/ test( "38623426,abaabababbaa", "-" );
/*64*/ test( "19312285,bbaababbaaba", "+" );
/*65*/ test( "11485959,baaaaababaaa", "-" );
/*66*/ test( "36831104,babbbbbbabab", "+" );

main.sql

-- case 13 254,babb の例
       WITH RECURSIVE rules(symbol, "no", angle) AS (
            VALUES('a', 1, 0), ('a', 2, 60), ('a', 3, -60), ('a', 4, 0),
                  ('b', 1, 0), ('b', 2, 60), ('b', 3, 0), ('b', 4, -60), ('b', 5, 0))

          , inputs AS (
     SELECT ROW_NUMBER() OVER() AS "no"
          , symbol
       FROM (VALUES('b'), ('a'), ('b'), ('b')) AS symbols(symbol))

          , t AS (
     SELECT Array[0] AS no
          , 0 AS angle

  UNION ALL

     SELECT t."no" || rules."no"
          , t.angle + rules.angle
       FROM t
       JOIN inputs ON ARRAY_LENGTH(t."no", 1) = inputs."no"
       JOIN rules ON rules.symbol = inputs.symbol)

     SELECT angle % 360 AS angle
       FROM t
      WHERE ARRAY_LENGTH(t."no", 1) - 1 = 4
   ORDER BY t."no"
     OFFSET 254 - 1
      LIMIT 1
;