63 lines
1.7 KiB
Scala
63 lines
1.7 KiB
Scala
package tf.bug.aoc.y2020
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import cats.effect._
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import cats.syntax.all._
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import fs2._
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import scala.collection.SortedSet
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import tf.bug.aoc.Day
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object Day5 extends Day:
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case class Seat(row: Int, col: Int) {
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def id = row * 8 + col
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}
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object Seat {
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implicit val seatOrdering: Ordering[Seat] = Ordering.by(_.id)
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}
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override def part1[F[_]: Async]: Pipe[F, String, String] =
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(lines: Stream[F, String]) => {
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lines.through(seats[F])
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.map(_.id)
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.fold1(_.max(_))
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.map(_.show)
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}
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override def part2[F[_]: Async]: Pipe[F, String, String] =
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(lines: Stream[F, String]) => {
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val sortedSeats: F[SortedSet[Seat]] =
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lines.through(seats[F])
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.compile.to(Collector.supportsFactory(SortedSet.evidenceIterableFactory[Seat]))
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val pairs: Stream[F, (Seat, Seat)] =
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Stream.eval(sortedSeats)
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.flatMap(seats => Stream.fromIterator[F](seats.sliding(2).map(set => (set.min, set.max)), 1))
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val gaps: Stream[F, Int] = pairs.collect {
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case (a, b) if a.id + 1 == b.id - 1 => a.id + 1
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}
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gaps.map(_.show)
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}
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def seats[F[_]: Async]: Pipe[F, String, Seat] =
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(lines: Stream[F, String]) => {
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lines
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.map { s =>
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val (row, col) = s.splitAt(7)
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val rowN = row.zipWithIndex.foldLeft(0) {
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case (n, ('F', _)) =>
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n
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case (n, ('B', i)) =>
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val range = 1 << (6 - i)
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n + range
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}
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val colN = col.zipWithIndex.foldLeft(0) {
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case (n, ('L', _)) =>
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n
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case (n, ('R', i)) =>
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val range = 1 << (2 - i)
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n + range
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}
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Seat(rowN, colN)
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}
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}
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