aoc 2022 9

2022-day9.scala

import scala.io.Source

case class Point(x: Int, y: Int)
object Point:
  def move(h: Point, t: Point, n: Point) =
    val head = Point(h.x + n.x, h.y + n.y)
    (head.x - t.x, head.y - t.y) match
      case (2, 2) => (head, Point(head.x - 1, head.y - 1))
      case (-2, 2) => (head, Point(head.x + 1, head.y - 1))
      case (2, -2) => (head, Point(head.x - 1, head.y + 1))
      case (-2, -2) => (head, Point(head.x + 1, head.y + 1))
      case (2, _) => (head, Point(head.x - 1, head.y))
      case (-2, _) => (head, Point(head.x + 1, head.y))
      case (_, 2) => (head, Point(head.x, head.y - 1))
      case (_, -2) => (head, Point(head.x, head.y + 1))
      case _ => (head, t)
  def move(rs: List[Point], n: Point): List[Point] = rs match
    case Nil => Nil
    case (h :: Nil) => rs
    case (h :: t :: rest) =>
      Point.move(h, t, n) match
        case (a, b) => a :: Point.move(b :: rest, Point(0, 0))
    
def moveRope(h: Point, t: Point, action: (Point, Int), result: List[Point]): (Point, Point, List[Point]) =
  action match 
    case (_, 0) => (h, t, result)
    case (p, n) =>
      val res = Point.move(h, t, p)
      moveRope(res._1, res._2, (p, n - 1), res._2 :: result)

def moveRope(ropes: List[Point], action: (Point, Int), result: List[Point]): (List[Point], List[Point]) =
  action match 
    case (_, 0) => (ropes, result)
    case (p, n) =>
      val res = Point.move(ropes, p)
      moveRope(res, (p, n - 1), res.last :: result)

def action(s: String): (Point, Int) =
  val command = s.split(" ")
  val action = command(0) match
    case "U" => Point(0, 1)
    case "D" => Point(0, -1)
    case "L" => Point(-1, 0)
    case "R" => Point(1, 0)
  (action, command(1).toInt)  

def ans1(xs: List[String]): Int =
  val x = xs.foldLeft((Point(0, 0), Point(0, 0), List(Point(0, 0))))(
    (acc, x) => acc match
      case (h, t, res) => moveRope(h, t, action(x), res)
  )
  x._3.toSet.size

def ans2(xs: List[String]): Int =
  val f = List(Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0),Point(0, 0))
  val x = xs.foldLeft((f, List[Point]()))(
    (acc, x) => acc match
      case (ropes, res) => moveRope(ropes, action(x), res)
  )
  x._2.toSet.size

def solve =
  val input = Source.fromFile("day9.txt").getLines.toList
  println(ans1(input))
  println(ans2(input))