feat(2024): day 5

2024/day05.scala

@@ -0,0 +1,28 @@
+package `2024`.day05
+
+import prelude.*
+
+def middle[A](xs: IndexedSeq[A]) = xs(xs.size / 2)
+
+@main def main() =
+  val (rawRules, rawPages) = readInput(this).mkString
+    .split("\n\n")
+    .map(_.split("\n")) match { case Array(a, b) => (a, b) }
+
+  given ord: Ordering[Int] = rawRules
+    .collect { case s"$a|$b" => a.toInt -> b.toInt }
+    .groupMap(_._1)(_._2)
+    .view
+    .mapValues(_.toSet)
+    .toMap
+    .withDefaultValue(Set())
+    |> (deps => Ordering.fromLessThan(deps(_)(_)))
+
+  val pages = rawPages.map(_.split(",").map(_.toInt).toVector).toVector
+
+  val (wrongs, rights) = pages.partitionMap { page =>
+    val sort = page.sorted
+    if page == sort then Right(sort) else Left(sort)
+  }
+  println(rights.sumBy(middle))
+  println(wrongs.sumBy(middle))