2023-18

jurisk · Dec 18, 2023 · 021cbbf · 021cbbf
1 parent 94e5d04
commit 021cbbf
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Showing 2 changed files with 31 additions and 25 deletions.
diff --git a/scala2/src/main/scala/jurisk/adventofcode/y2023/Advent18.scala b/scala2/src/main/scala/jurisk/adventofcode/y2023/Advent18.scala
@@ -1,7 +1,6 @@
 package jurisk.adventofcode.y2023
 
-import cats.implicits.catsSyntaxUnorderedFoldableOps
-import jurisk.algorithms.pathfinding.Bfs
+import cats.implicits._
 import jurisk.geometry._
 import jurisk.utils.FileInput._
 import jurisk.utils.Parsing.StringOps
@@ -62,27 +61,17 @@ object Advent18 {
   }
 
   def solveFloodFill(data: List[MovementInstruction]): Long = {
-    var field = Field2D
-      .fromPoints(
-        MovementInstruction.walkEveryPoint(data),
-        {
-          case true  => Square.Dug
-          case false => Square.Unknown
-        },
-      )
+    val field = Field2D
+      .fromPoints(MovementInstruction.walkEveryPoint(data))
+      .map(if (_) Square.Dug else Square.Unknown)
 
-    field = field.expandOneSquareInAllDirections(Square.Unknown)
-
-    // TODO: Field2D has Field2D.floodFillCoordinates that you could also have floodFillFromOutside with just f: T => Boolean ?
-
-    val next = Field2D.floodFillField[Square](
+    val filled = Field2D.floodFillFromOutside[Square](
       field,
-      field.topLeft,
-      (_, to) => to == Square.Unknown,
-      Square.Outside,
+      outside = Square.Unknown,
+      mark = Square.Outside,
     )
 
-    next.count(x => x == Square.Dug || x == Square.Unknown)
+    filled.count(_ != Square.Outside)
   }
 
   def solvePicksShoelace(data: List[MovementInstruction]): Long = {

diff --git a/scala2/src/main/scala/jurisk/geometry/Field2D.scala b/scala2/src/main/scala/jurisk/geometry/Field2D.scala
@@ -269,6 +269,9 @@ final case class Field2D[T] private (
       acc.updatedAtUnsafe(c + Direction2D.SE, v)
     }
   }
+
+  def contractOneSquareInAllDirections: Field2D[T] =
+    Field2D(data.tail.init.map(_.tail.init))
 }
 
 object Field2D {
@@ -298,15 +301,14 @@ object Field2D {
       topLeft,
     )
 
-  def fromPoints[T: ClassTag](
-    points: Seq[Coords2D],
-    f: Boolean => T,
-  ): Field2D[T] = {
+  def fromPoints(
+    points: Seq[Coords2D]
+  ): Field2D[Boolean] = {
     val boundingBox = Area2D.boundingBoxInclusive(points)
-    val field       = Field2D.forArea(boundingBox, f(false))
+    val field       = Field2D.forArea(boundingBox, false)
 
     points.foldLeft(field) { case (acc, c) =>
-      acc.updatedAtUnsafe(c, f(true))
+      acc.updatedAtUnsafe(c, true)
     }
   }
 
@@ -330,6 +332,21 @@ object Field2D {
       },
   )
 
+  def floodFillFromOutside[T: ClassTag](
+    field: Field2D[T],
+    outside: T,
+    mark: T,
+  ): Field2D[T] = {
+    val expanded = field.expandOneSquareInAllDirections(outside)
+    val filled   = floodFillField[T](
+      expanded,
+      expanded.topLeft,
+      (_, to) => to == outside,
+      mark,
+    )
+    filled.contractOneSquareInAllDirections
+  }
+
   def floodFillField[T](
     field: Field2D[T],
     seed: Coords2D,