Day 01

.gitignore

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+# macOS
+.DS_Store
+
+# sbt specific
+dist/*
+target/
+lib_managed/
+src_managed/
+project/boot/
+project/plugins/project/
+project/local-plugins.sbt
+.history
+.ensime
+.ensime_cache/
+.sbt-scripted/
+local.sbt
+
+# Bloop
+.bsp
+
+# VS Code
+.vscode/
+
+# Metals
+.bloop/
+.metals/
+metals.sbt
+
+# IDEA
+.idea
+.idea_modules
+/.worksheet/

.scalafmt.conf

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+version = "3.7.15"
+runner.dialect = scala3

build.sbt

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+val scala3Version = "3.5.2"
+
+lazy val root = project
+  .in(file("."))
+  .settings(
+    name := "aoc-2024",
+    version := "0.1.0-SNAPSHOT",
+    scalaVersion := scala3Version,
+    libraryDependencies += "org.scalameta" %% "munit" % "1.0.0" % Test
+  )

project/build.properties

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+sbt.version=1.10.5

src/main/scala/Main.scala

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+package dev.ctsk.aoc
+
+import dev.ctsk.aoc.days._
+
+val solvers = Map[Int, Solver](
+  1 -> Day01
+)
+
+@main def main(day: String, input: String): Unit =
+  solvers.get(day.toInt) match
+    case Some(solver) =>
+      val (timings, solution) = solver.run(input)
+      println(f"Preprocessing: ${timings.prep}%24s μs")
+      println(f"Part 1: ${solution.p1}%15s ${timings.p1}%15s μs")
+      println(f"Part 2: ${solution.p2}%15s ${timings.p2}%15s μs")
+
+    case None =>
+      println(s"Day $day not solved")

src/main/scala/Solution.scala

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+package dev.ctsk.aoc
+
+case class Timings(prep: Long, p1: Long, p2: Long)
+
+case class Solution(p1: String, p2: String)
+
+abstract class Solver(day: Int):
+  def run(input: String): (Timings, Solution)
+
+  def timed[A](solution: => A): (Long, A) =
+    val start = System.nanoTime()
+    val result = solution
+    val end = System.nanoTime()
+
+    ((end - start) / 1000, result)

src/main/scala/days/Day01.scala

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+package dev.ctsk.aoc.days
+
+import dev.ctsk.aoc._
+
+object Day01 extends Solver(1):
+  type Input = (Array[Int], Array[Int])
+
+  def pre(input: String): Input =
+    io.Source
+      .fromFile(input)
+      .getLines()
+      .map { case s"$i   $j" => (i.toInt, j.toInt) }
+      .toArray
+      .unzip match { case (left, right) => (left.sorted, right.sorted) }
+
+  def part1(input: Input): String =
+    input match
+      case (left, right) => left.zip(right).map(_ - _).map(_.abs).sum.toString
+
+  def part2(input: Input): String =
+    val (left, right) = input;
+    val counts = right.groupBy(identity).mapValues(_.length).toMap
+    left.map(n => n * counts.getOrElse(n, 0)).sum.toString
+
+  def run(input: String): (Timings, Solution) =
+    val (pre_time, pre_input) = timed { pre(input) }
+    val (p1_time, p1_solution) = timed { part1(pre_input) }
+    val (p2_time, p2_solution) = timed { part2(pre_input) }
+
+    (Timings(pre_time, p1_time, p2_time), Solution(p1_solution, p2_solution))

src/test/scala/MySuite.scala

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+// For more information on writing tests, see
+// https://scalameta.org/munit/docs/getting-started.html
+class MySuite extends munit.FunSuite {
+  test("example test that succeeds") {
+    val obtained = 42
+    val expected = 42
+    assertEquals(obtained, expected)
+  }
+}