Day3.scala

package sungkmi.aoc2020.day3

import scala.collection.JavaConverters._

def count(dr: Int, dc: Int): Int =
  @annotation.tailrec
  def loop(r: Int, c: Int, acc: Int): Int =
    //println((r, c))
    if (r >= rMax) acc else
      val current = map(r)(c) match
        case '.' => 0
        case '#' => 1
      loop(r + dr, (c + dc) % cMax, acc + current)
  loop(0,0,0)

@main def part1: Unit =
  val ans = count(2, 1)
  println(ans)

@main def part2: Unit =
  val subans = Seq((1, 1), (3, 1), (5, 1), (7, 1), (1, 2)).map{
    case (right, down) => BigInt(count(down, right))
  }
  val ans = subans.product
  println(ans)

lazy val map: IndexedSeq[IndexedSeq[Char]] = xs.map(_.trim.toIndexedSeq)
lazy val rMax = map.size
lazy val cMax = map(0).size

lazy val xs = input.trim.lines.iterator().asScala.toVector

// lazy val input = """.#....#..##.#..####....#......."""