Solve 2023 day 23 using key neighbors

sim642 · Dec 23, 2023 · d4e8245 · d4e8245
1 parent 4946473
commit d4e8245
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Showing 2 changed files with 52 additions and 15 deletions.
diff --git a/src/main/scala/eu/sim642/adventofcode2023/Day23.scala b/src/main/scala/eu/sim642/adventofcode2023/Day23.scala
@@ -1,13 +1,14 @@
 package eu.sim642.adventofcode2023
 
 import eu.sim642.adventofcodelib.Grid
-import eu.sim642.adventofcodelib.graph.{BFS, GraphTraversal, UnitNeighbors}
+import eu.sim642.adventofcodelib.graph.{BFS, Dijkstra, GraphTraversal, UnitNeighbors}
 import eu.sim642.adventofcodelib.pos.Pos
 import eu.sim642.adventofcodelib.GridImplicits.*
+import eu.sim642.adventofcodelib.box.Box
 
 object Day23 {
 
-  case class HikePos(pos: Pos, path: Set[Pos])
+  case class HikePos(pos: Pos, path: List[Pos], pathSet: Set[Pos])
 
   private val slopeOffsets = Map(
     '^' -> Pos(0, -1),
@@ -18,27 +19,63 @@ object Day23 {
 
   def longestHike(grid: Grid[Char], slopes: Boolean = true): Int = {
 
-    val graphTraversal = new GraphTraversal[HikePos] with UnitNeighbors[HikePos] {
-      override val startNode: HikePos = HikePos(Pos(1, 0), Set(Pos(1, 0))) // TODO: don't hardcode
+    val startPos = Pos(1, 0) // TODO: don't hardcode
+    val targetPos = Pos(grid(0).size - 2, grid.size - 1)
+
+    val branchPoss = (for {
+      pos <- Box(Pos(1, 1), Pos(grid(0).size - 2, grid.size - 2)).iterator
+      if grid(pos) != '#'
+      if Pos.axisOffsets.count(offset => grid(pos + offset) != '#') > 2
+    } yield pos).toSet
+
+    val keyPoss = branchPoss + startPos + targetPos
+    println(keyPoss)
+
+    val keyNeighbors: Map[Pos, Map[Pos, Int]] = {
+      keyPoss.view.map({ fromPos =>
+
+        val graphTraversal = new GraphTraversal[Pos] with UnitNeighbors[Pos] {
+          override val startNode: Pos = fromPos
 
-      override def unitNeighbors(hikePos: HikePos): IterableOnce[HikePos] = {
-        val HikePos(pos, path) = hikePos
+          override def unitNeighbors(pos: Pos): IterableOnce[Pos] = {
+            if (pos != fromPos && keyPoss(pos))
+              Iterator.empty
+            else {
+              for {
+                offset <- if (!slopes || grid(pos) == '.') Pos.axisOffsets else Seq(slopeOffsets(grid(pos)))
+                newPos = pos + offset
+                if grid.containsPos(newPos)
+                if grid(newPos) != '#'
+              } yield newPos
+            }
+          }
+        }
+
+        val distances = BFS.traverse(graphTraversal).distances.toMap
+        fromPos -> distances.filter(p => p._1 != fromPos && keyPoss(p._1))
+      }).toMap
+    }
+
+    val graphTraversal = new GraphTraversal[HikePos] {
+      override val startNode: HikePos = HikePos(startPos, List(startPos), Set(startPos))
+
+      override def neighbors(hikePos: HikePos): IterableOnce[(HikePos, Int)] = {
+        val HikePos(pos, path, pathSet) = hikePos
         for {
-          offset <- if (!slopes || grid(pos) == '.') Pos.axisOffsets else Seq(slopeOffsets(grid(pos)))
-          newPos = pos + offset
-          if grid.containsPos(newPos)
-          if grid(newPos) != '#'
+          (newPos, dist) <- keyNeighbors(pos)
+          //() = println((pos, newPos, dist))
+          //() = assert(slopes || keyNeighbors(newPos)(pos) == dist)
           if !path.contains(newPos)
-        } yield HikePos(newPos, path + newPos)
+        } yield HikePos(newPos, newPos :: path, pathSet + newPos) -> dist
       }
     }
 
-    val targetPos = Pos(grid(0).size - 2, grid.size - 1)
 
-    val asd = BFS.traverse(graphTraversal).distances
+    val asd = Dijkstra.traverse(graphTraversal).distances
       .filter(_._1.pos == targetPos)
 
     asd.values.toSet.foreach(println)
+    println(asd.maxBy(_._2)._1.path)
     asd
       .values
       .max

diff --git a/src/test/scala/eu/sim642/adventofcode2023/Day23Test.scala b/src/test/scala/eu/sim642/adventofcode2023/Day23Test.scala
@@ -34,7 +34,7 @@ class Day23Test extends AnyFunSuite {
     assert(longestHike(parseGrid(exampleInput)) == 94)
   }
 
-  ignore("Part 1 input answer") { // TODO: optimize
+  test("Part 1 input answer") { // TODO: optimize
     assert(longestHike(parseGrid(input)) == 2414)
   }
 
@@ -43,6 +43,6 @@ class Day23Test extends AnyFunSuite {
   }
 
   ignore("Part 2 input answer") { // TODO: optimize
-    assert(longestHike(parseGrid(input), slopes = false) == 2414)
+    //assert(longestHike(parseGrid(input), slopes = false) == 2414)
   }
 }