Advent of Code 2022-8.scala

import java.io.FileInputStream
import scala.annotation.{tailrec, targetName}
import scala.io.StdIn

case class Point(x: Int, y: Int) {
  def +(that: Point): Point = Point(this.x + that.x, this.y + that.y)
}
case class Map(element: Vector[Vector[Int]]) {
  @tailrec
  private def _iterate[T](position: Point, delta: Point, start: Int, acc: T, iterate: (T, Int, Int) => T): T = {
    if 0 > position.x || 0 > position.y || position.x >= element(0).size || position.y >= element.size then
      acc
    else
      val target = element(position.y)(position.x)
      val nextAcc = iterate(acc, start, target)
      _iterate(position + delta, delta, start, nextAcc, iterate)
  }

  def iterateAndFold[T, R](acc: T, iterate: (T, Int, Int) => T, foldAcc: R, foldOp: (R, T) => R): Vector[Vector[R]] = {
    element.zipWithIndex.map { case (row, y) =>
      row.zipWithIndex.map { case (v, x) =>
        val position = Point(x, y)
        val start = element(y)(x)
        Vector(Point(1, 0), Point(0, 1), Point(-1, 0), Point(0, -1)).map(delta => _iterate(position + delta, delta, start, acc, iterate)).foldLeft(foldAcc)(foldOp)
      }
    }
  }
}

def solve8_1(input: Map): Int =
  val visibility: Vector[Vector[Boolean]] = input.iterateAndFold(true, (acc, start, target) => acc && start > target, false, (acc, v) => acc || v)
  visibility.map(_.count(_ == true)).sum

def solve8_2(input: Map): Int =
  val visibility: Vector[Vector[Int]] = input.iterateAndFold((true, 0), (acc, start, target) => {
    acc match {
      case (true, v) =>
        if start > target then
          (true, acc._2 + 1)
        else
          (false, acc._2 + 1)
      case _ =>
        acc
    }
  }, 1, (acc, v) => acc * v._2)
  visibility.map(_.max).max



@main def solve8(): Unit =
  val in = new FileInputStream("example8-2.in")
  System.setIn(in)
  val inputs = Iterator.continually(StdIn.readLine())
    .takeWhile(line => null != line)
    .map(line => line.map(_ - '0').toVector)
    .toVector
  val input = Map(inputs)
  println(solve8_1(input))
  println(solve8_2(input))