feat(day20): both parts

Author: fdlk

day20.sc

@@ -0,0 +1,63 @@
+import common.loadPackets
+
+val input = loadPackets(List("day20.txt"))
+val imageEnhancementAlgorithm = input.head.map({
+  case '#' => 1
+  case '.' => 0
+})
+
+case class Point(x: Int, y: Int) {
+  def neighbors: IndexedSeq[Point] =
+    for (dy <- -1 to 1;
+         dx <- -1 to 1)
+    yield copy(x + dx, y + dy)
+}
+type Image = Map[Point, Int]
+
+val image: Image = input.drop(2).zipWithIndex.flatMap {
+  case (row, y) => row.zipWithIndex.map {
+    case ('#', x) => Point(x, y) -> 1
+    case ('.', x) => Point(x, y) -> 0
+  }
+}.toMap
+
+def enhance(point: Point, image: Image, defaultLit: Int): Int = {
+  val index = point.neighbors.map(neighbor => image.getOrElse(neighbor, defaultLit)).mkString
+  imageEnhancementAlgorithm(Integer.parseInt(index, 2))
+}
+
+type State = (Image, Int)
+
+def next(state: State): State = state match {
+  case (image, defaultLit) =>
+    val xs = image.keySet.map(_.x)
+    val ys = image.keySet.map(_.y)
+    val nextImage = (for (x <- xs.min - 2 to xs.max + 2;
+          y <- ys.min - 2 to ys.max + 2)
+    yield Point(x, y))
+        .map(p => (p, enhance(p, image, defaultLit))).toMap
+    (nextImage, 1-defaultLit)
+}
+
+val initial: State = (image, 0)
+val (part1,_) = next(next(initial))
+part1.values.count(_ == 1)
+
+def printImage(image: Map[Point, Int]): Unit = {
+  val xs = image.keySet.map(_.x)
+  val ys = image.keySet.map(_.y)
+
+  val points = for (y <- ys.min to ys.max;
+        x <- xs.min to xs.max)
+  yield if(image(Point(x,y)) == 1) '#' else '.'
+
+  points.grouped(xs.max - xs.min + 1)
+    .foreach(x => println(x.mkString))
+}
+
+printImage(part1)
+val iterations = LazyList.iterate(initial)(next)
+
+val (part2,_) = iterations.drop(50).head
+part2.values.count(_ == 1)
+printImage(part2)

src/main/resources/day20.txt

@@ -0,0 +1,102 @@
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