Day03.scala

package aoc2020

object Day03:
  type InputType = Array[Array[Char]]

  private def ready(input: String): InputType =
    input.linesIterator
      .map(_.trim)
      .filter(_.nonEmpty)
      .map(_.toCharArray)
      .toArray
  
  @main
  def solution: Unit =
    var testData: InputType = time("testReady", () => ready(testInput))
    time("testSolve1", () => solve1(3, 1)(testData)) // should be 7
    time("testSolve2", () => solve2(testData)) // should be 336

    var data: InputType = time("ready", () => ready(input))
    time("solve1", () => solve1(3, 1)(data))
    time("solve2", () => solve2(data))

  private def solve1(dx: Int, dy: Int)(implicit data: InputType): Long =
    solve11(0, 0)(dx, dy)

  private def solve11(x: Int, y: Int)(dx: Int, dy: Int)(implicit slope: InputType): Int = {
    if (y >= slope.length) return 0
    val xx = x % slope(y).length
    (if (slope(y)(xx) == '#') 1 else 0) + solve11(xx + dx, y + dy)(dx, dy)
  }

  private def solve2(implicit data: InputType): Long =
    val steps: Array[(Int, Int)] = Array(
      (1, 1), (3, 1), (5, 1), (7, 1), (1, 2)
    )
    steps.map(st => solve1(st._1, st._2).toLong).product

  private val testInput =
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      |""".stripMargin

  private val input =
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