Day 5

aoc/src/Day5.scala

@@ -0,0 +1,64 @@
+import scala.io.Source
+
+object Day5 extends App:
+
+  val input = Source
+    .fromURL(getClass.getResource("day5Input.txt"))
+    .mkString
+
+  final case class Coordinates(x: Int, y: Int)
+  object Coordinates:
+    def parse(input: String): Coordinates =
+      input.split(',') match
+        case Array(x, y) => Coordinates(x.toInt, y.toInt)
+
+  final case class Line(from: Coordinates, to: Coordinates):
+    def spannedCoordinates: Seq[Coordinates] =
+      if (from.x == to.x)
+        Range
+          .inclusive(from.y, to.y, if (from.y < to.y) 1 else -1)
+          .map(Coordinates(from.x, _))
+      else if (from.y == to.y)
+        Range
+          .inclusive(from.x, to.x, if (from.x < to.x) 1 else -1)
+          .map(Coordinates(_, from.y))
+      else
+        Seq()
+
+    def spannedCoordinatesIncludingDiagonal: Seq[Coordinates] =
+      val xs =
+        if (from.x == to.x) LazyList.continually(from.x)
+        else Range.inclusive(from.x, to.x, if (from.x < to.x) 1 else -1)
+      val ys =
+        if (from.y == to.y) LazyList.continually(from.y)
+        else
+          Range.inclusive(from.y, to.y, if (from.y < to.y) 1 else -1)
+
+      xs.zip(ys).map(Coordinates.apply).toList
+
+  object Line:
+    def parse(input: String): Line =
+      input.split(" -> ") match
+        case Array(from, to) =>
+          Line(Coordinates.parse(from), Coordinates.parse(to))
+
+  val lines = input
+    .split('\n')
+    .map(Line.parse)
+    .toList
+
+  def countDuplicated(coordinates: Seq[Coordinates]): Int =
+    coordinates
+      .groupMapReduce(identity)(_ => 1)(_ + _)
+      .values
+      .filter(_ > 1)
+      .size
+
+  val overlappingPoints = countDuplicated(lines.flatMap(_.spannedCoordinates))
+
+  println(s"Part 1: $overlappingPoints")
+
+  val overlappingPointsIncludingDiagonal = countDuplicated(
+    lines.flatMap(_.spannedCoordinatesIncludingDiagonal)
+  )
+  println(s"Part 2: $overlappingPointsIncludingDiagonal")