add day 22 code? (#793)

Author: merlinorg

2024/src/day22.scala

@@ -0,0 +1,67 @@
+package day22
+
+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/day22")
+
+def part1(input: String): Long =
+  input.linesIterator.foldMap: line =>
+    line.toLong.secretsIterator.nth(2000)
+
+def part2(input: String): Long =
+  val deltaTotals = input.linesIterator.foldMap: line =>
+    monkeyMap(line)
+  deltaTotals.values.max
+
+def monkeyMap(line: String): Map[(Long, Long, Long, Long), Long] =
+  given Semigroup[Long] = leftBiasedSemigroup
+  line.toLong.secretsIterator.map(_ % 10).take(2000).sliding(5).foldMap: quintuple =>
+    Map(deltaQuartuple(quintuple) -> quintuple(4))
+
+def deltaQuartuple(q: Seq[Long]): (Long, Long, Long, Long) =
+  (q(1) - q(0), q(2) - q(1), q(3) - q(2), q(4) - q(3))
+
+extension (self: Long)
+  private inline def step(f: Long => Long): Long = mix(f(self)).prune
+  private inline def mix(n: Long): Long          = self ^ n
+  private inline def prune: Long                 = self % 16777216
+  private inline def nextSecret: Long            = step(_ * 64).step(_ / 32).step(_ * 2048)
+
+  def secretsIterator: Iterator[Long] =
+    Iterator.iterate(self)(_.nextSecret)
+
+trait Semigroup[A]:
+  def combine(a0: A, a1: A): A
+
+trait Monoid[A] extends Semigroup[A]:
+  def zero: A
+
+given NumericMonoid[A](using N: Numeric[A]): Monoid[A] with
+  def zero: A                  = N.zero
+  def combine(a0: A, a1: A): A = N.plus(a0, a1)
+
+given MapMonoid[A, B](using S: Semigroup[B]): Monoid[Map[A, B]] with
+  def zero: Map[A, B] = Map.empty
+
+  def combine(ab0: Map[A, B], ab1: Map[A, B]): Map[A, B] =
+    ab1.foldLeft(ab0):
+      case (ab, (a1, b1)) =>
+        ab.updatedWith(a1):
+          case Some(b0) => Some(S.combine(b0, b1))
+          case None     => Some(b1)
+
+def leftBiasedSemigroup[A]: Semigroup[A] = (a0: A, _: A) => a0
+
+extension [A](self: Iterator[A])
+  def nth(n: Int): A                                    =
+    self.drop(n).next()
+
+  def foldMap[B](f: A => B)(using M: Monoid[B]): B =
+    self.map(f).foldLeft(M.zero)(M.combine)