Advent of Code 2021-2.scala

import java.io.FileInputStream
import scala.annotation.tailrec
import scala.io.StdIn

case class Submarine(depth: Int = 0, position: Int = 0, aim: Int = 0)

def solve2_1(inputs: Vector[String]): Int = {
  val submarine = inputs.foldLeft(Submarine()) { (submarine, x) =>
    val Array(command, nString) = x.split(" ")
    val n = nString.toInt
    command match {
      case "forward" =>
        submarine.copy(position = submarine.position + n)
      case "down" =>
        submarine.copy(depth = submarine.depth + n)
      case "up" =>
        submarine.copy(depth = submarine.depth - n)
    }
  }
  submarine.depth * submarine.position
}

def solve2_2(inputs: Vector[String]): Int = {
  val submarine = inputs.foldLeft(Submarine()) { (submarine, x) =>
    val Array(command, nString) = x.split(" ")
    val n = nString.toInt
    command match {
      case "forward" =>
        submarine.copy(position = submarine.position + n, depth = submarine.depth + submarine.aim * n)
      case "down" =>
        submarine.copy(aim = submarine.aim + n)
      case "up" =>
        submarine.copy(aim = submarine.aim - n)
    }
  }
  submarine.depth * submarine.position
}

@main def solve2(): Unit =
  val in = new FileInputStream("example2-2.in")
  System.setIn(in)
  val inputs = Iterator.continually(StdIn.readLine())
    .takeWhile(line => null != line && line.trim.nonEmpty)
    .toVector
  println(solve2_1(inputs))
  println(solve2_2(inputs))