feat: prepare for interactive 2024 solution

2024/src/day13.scala

@@ -0,0 +1,48 @@
+package day13
+
+import locations.Directory.currentDir
+import inputs.Input.loadFileSync
+
+@main def part1: Unit =
+  println(s"The solution is ${part1(loadInput())}")
+
+@main def part2: Unit =
+  println(s"The solution is ${part2(loadInput())}")
+
+def loadInput(): String = loadFileSync(s"$currentDir/../input/day13")
+
+case class Claw(ax: Long, ay: Long, bx: Long, by: Long, x: Long, y: Long):
+  def solve: Option[Long] = for
+    b <- (x * ay - y * ax) safeDiv (bx * ay - by * ax)
+    a <- (x - b * bx) safeDiv ax
+  yield a * 3 + b
+
+object Claw:
+  def parse(xs: Seq[String]): Option[Claw] = xs match
+    case Seq(
+          s"Button A: X+${L(ax)}, Y+${L(ay)}",
+          s"Button B: X+${L(bx)}, Y+${L(by)}",
+          s"Prize: X=${L(x)}, Y=${L(y)}",
+        ) =>
+      Some(Claw(ax, ay, bx, by, x, y))
+    case _ => None
+
+def parse(input: String): Seq[Claw] =
+  input.split("\n+").toSeq.grouped(3).flatMap(Claw.parse).toSeq
+
+extension (a: Long)
+  infix def safeDiv(b: Long): Option[Long] =
+    Option.when(b != 0 && a % b == 0)(a / b)
+
+object L:
+  def unapply(s: String): Option[Long] = s.toLongOption
+
+def part1(input: String): Long =
+  parse(input).flatMap(_.solve).sum
+
+def part2(input: String): Long =
+  val diff = 10_000_000_000_000L
+  parse(input)
+    .map(c => c.copy(x = c.x + diff, y = c.y + diff))
+    .flatMap(_.solve)
+    .sum

2024/src/inputs.scala

@@ -0,0 +1,9 @@
+package inputs
+
+import scala.util.Using
+import scala.io.Source
+
+object Input:
+
+  def loadFileSync(path: String): String =
+    Using.resource(Source.fromFile(path))(_.mkString)

2024/src/locations.scala

@@ -0,0 +1,19 @@
+package locations
+
+import scala.quoted.*
+
+object Directory:
+
+  /** The absolute path of the parent directory of the file that calls this method
+    * This is stable no matter which directory runs the program.
+    */
+  inline def currentDir: String = ${ parentDirImpl }
+
+  private def parentDirImpl(using Quotes): Expr[String] =
+    // position of the call to `currentDir` in the source code
+    val position = quotes.reflect.Position.ofMacroExpansion
+    // get the path of the file calling this macro
+    val srcFilePath = position.sourceFile.getJPath.get
+    // get the parent of the path, which is the directory containing the file
+    val parentDir = srcFilePath.getParent().toAbsolutePath
+    Expr(parentDir.toString) // convert the String to Expr[String]