Patch some of the wrong orderings

Author: fwcd

day21/src/day21.scala

@@ -52,7 +52,24 @@ extension (ptype: PadType) {
     while !queue.isEmpty do
       val node = queue.dequeue()
       if node.pos == endPos then
-        return node.program.appended('A')
+        // Annoying edge cases, what rule do they follow?
+        return Map(
+          (">>^", "^>>"),
+          ("vv<", "<vv"),
+          ("vv>v", ">vvv"),
+          (">>v", "v>>"),
+          ("vvv<", "<vvv"),
+          ("vv<", "<vv"),
+          ("<^<", "^<<"),
+          ("^^<", "<^^"),
+          ("^^^<", "<^^^"),
+          ("<v<", "v<<"),
+          ("<^^", "^<^"),
+          ("<^^^", "^^^<"),
+          ("v>>", ">>v"),
+          ("^>>", ">>^"),
+        ).getOrElse(node.program, node.program)
+          .appended('A')
 
       for action <- List('<', '^', 'v', '>') do
         val dir = DIRECTIONS(action)
@@ -201,6 +218,139 @@ def solve(robots: Int, goals: List[String], func: (Int, String) => Int): Int =
 
 val SHORTEST_PATHS = PadType.Num.shortestPaths ++ PadType.Dir.shortestPaths
 
+val SHORTEST_PATHS_2 = Map(
+  (('A', '0'), "<A"),
+  (('0', 'A'), ">A"),
+  (('A', '1'), "^<<A"),
+  (('1', 'A'), ">>vA"),
+  (('A', '2'), "<^A"),
+  (('2', 'A'), "v>A"),
+  (('A', '3'), "^A"),
+  (('3', 'A'), "vA"),
+  (('A', '4'), "^^<<A"),
+  (('4', 'A'), ">>vvA"),
+  (('A', '5'), "<^^A"),
+  (('5', 'A'), "vv>A"),
+  (('A', '6'), "^^A"),
+  (('6', 'A'), "vvA"),
+  (('A', '7'), "^^^<<A"),
+  (('7', 'A'), ">>vvvA"),
+  (('A', '8'), "<^^^A"),
+  (('8', 'A'), "vvv>A"),
+  (('A', '9'), "^^^A"),
+  (('9', 'A'), "vvvA"),
+  (('0', '1'), "^<A"),
+  (('1', '0'), ">vA"),
+  (('0', '2'), "^A"),
+  (('2', '0'), "vA"),
+  (('0', '3'), "^>A"),
+  (('3', '0'), "<vA"),
+  (('0', '4'), "^<^A"),
+  (('4', '0'), ">vvA"),
+  (('0', '5'), "^^A"),
+  (('5', '0'), "vvA"),
+  (('0', '6'), "^^>A"),
+  (('6', '0'), "<vvA"),
+  (('0', '7'), "^^^<A"),
+  (('7', '0'), ">vvvA"),
+  (('0', '8'), "^^^A"),
+  (('8', '0'), "vvvA"),
+  (('0', '9'), "^^^>A"),
+  (('9', '0'), "<vvvA"),
+  (('1', '2'), ">A"),
+  (('2', '1'), "<A"),
+  (('1', '3'), ">>A"),
+  (('3', '1'), "<<A"),
+  (('1', '4'), "^A"),
+  (('4', '1'), "vA"),
+  (('1', '5'), "^>A"),
+  (('5', '1'), "<vA"),
+  (('1', '6'), "^>>A"),
+  (('6', '1'), "<<vA"),
+  (('1', '7'), "^^A"),
+  (('7', '1'), "vvA"),
+  (('1', '8'), "^^>A"),
+  (('8', '1'), "<vvA"),
+  (('1', '9'), "^^>>A"),
+  (('9', '1'), "<<vvA"),
+  (('2', '3'), ">A"),
+  (('3', '2'), "<A"),
+  (('2', '4'), "<^A"),
+  (('4', '2'), "v>A"),
+  (('2', '5'), "^A"),
+  (('5', '2'), "vA"),
+  (('2', '6'), "^>A"),
+  (('6', '2'), "<vA"),
+  (('2', '7'), "<^^A"),
+  (('7', '2'), "vv>A"),
+  (('2', '8'), "^^A"),
+  (('8', '2'), "vvA"),
+  (('2', '9'), "^^>A"),
+  (('9', '2'), "<vvA"),
+  (('3', '4'), "<<^A"),
+  (('4', '3'), "v>>A"),
+  (('3', '5'), "<^A"),
+  (('5', '3'), "v>A"),
+  (('3', '6'), "^A"),
+  (('6', '3'), "vA"),
+  (('3', '7'), "<<^^A"),
+  (('7', '3'), "vv>>A"),
+  (('3', '8'), "<^^A"),
+  (('8', '3'), "vv>A"),
+  (('3', '9'), "^^A"),
+  (('9', '3'), "vvA"),
+  (('4', '5'), ">A"),
+  (('5', '4'), "<A"),
+  (('4', '6'), ">>A"),
+  (('6', '4'), "<<A"),
+  (('4', '7'), "^A"),
+  (('7', '4'), "vA"),
+  (('4', '8'), "^>A"),
+  (('8', '4'), "<vA"),
+  (('4', '9'), "^>>A"),
+  (('9', '4'), "<<vA"),
+  (('5', '6'), ">A"),
+  (('6', '5'), "<A"),
+  (('5', '7'), "<^A"),
+  (('7', '5'), "v>A"),
+  (('5', '8'), "^A"),
+  (('8', '5'), "vA"),
+  (('5', '9'), "^>A"),
+  (('9', '5'), "<vA"),
+  (('6', '7'), "<<^A"),
+  (('7', '6'), "v>>A"),
+  (('6', '8'), "<^A"),
+  (('8', '6'), "v>A"),
+  (('6', '9'), "^A"),
+  (('9', '6'), "vA"),
+  (('7', '8'), ">A"),
+  (('8', '7'), "<A"),
+  (('7', '9'), ">>A"),
+  (('9', '7'), "<<A"),
+  (('8', '9'), ">A"),
+  (('9', '8'), "<A"),
+  (('<', '^'), ">^A"),
+  (('^', '<'), "v<A"),
+  (('<', 'v'), ">A"),
+  (('v', '<'), "<A"),
+  (('<', '>'), ">>A"),
+  (('>', '<'), "<<A"),
+  (('<', 'A'), ">>^A"),
+  (('A', '<'), "v<<A"),
+  (('^', 'v'), "vA"),
+  (('v', '^'), "^A"),
+  (('^', '>'), "v>A"),
+  (('>', '^'), "<^A"),
+  (('^', 'A'), ">A"),
+  (('A', '^'), "<A"),
+  (('v', '>'), ">A"),
+  (('>', 'v'), "<A"),
+  (('v', 'A'), "^>A"),
+  (('A', 'v'), "<vA"),
+  (('>', 'A'), "^A"),
+  (('A', '>'), "vA"),
+)
+
 def shortestProgramLengthClever(robots: Int, goal: String): Int =
   // TODO: Memoize
   if robots < 0 then
@@ -224,8 +374,9 @@ def moveCount(robots: Int, current: Char, next: Char): Int =
   // println(s"Part 1: ${solve(2, goals)}")
   // println(s"Part 2: ${solve(25, goals)}")
 
-  for p <- SHORTEST_PATHS.toList.sorted do
-    println(p)
+  for (k, p) <- SHORTEST_PATHS.toList.sorted do
+    if k._1 != k._2 && p != SHORTEST_PATHS_2(k) then
+      println(s"(\"$p\", \"${SHORTEST_PATHS_2(k)}\")")
 
   for i <- (0 to 3) do
     println(s"${solve(i, goals, { (r, g) => shortestProgram(r, g).length })} vs ${solve(i, goals, shortestProgramLength)} vs ${solve(i, goals, shortestProgramLengthClever)}")