Advent of Code 03 part 2.scala

import java.io.FileInputStream
import scala.io.StdIn

@main def solve3() =
  case class Vector2(x: Int, y: Int)
  
  def solve(trees: Vector[Vector[Char]], delta: Vector2, x: Int = 0, y: Int = 0, count: Int = 0): BigInt = {
    if trees.size - 1 <= y then
      count
    else
      val nextX = x + delta.x
      val nextY = y + delta.y
      val nextCount = if '#' == trees(nextY)(nextX % trees(nextY).size) then
        count + 1
      else
        count
      solve(trees, delta, nextX, nextY, nextCount)
  }


  val in = new FileInputStream("example3-1.in")
  System.setIn(in)

  val inputs = Iterator.continually(StdIn.readLine()).takeWhile(_ != null).map(_.toVector).toVector
  val slopes = Vector(Vector2(1, 1), Vector2(3, 1), Vector2(5, 1), Vector2(7, 1), Vector2(1, 2))
  val answers = slopes.map { solve(inputs, _) }
  println(answers.reduce(_ * _))