Advent of Code 2023-6.scala

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

def minAnswer(a: Double, b: Double, c: Double): Double =
  (-b + Math.sqrt(b * b - 4 * a * c)) / (2 * a)

def maxAnswer(a: Double, b: Double, c: Double): Double =
  (-b - Math.sqrt(b * b - 4 * a * c)) / (2 * a)

def answer(time: BigInt, distance: BigInt): Int =
  val min = minAnswer(-1, time.toDouble, -distance.toDouble)
  val max = maxAnswer(-1, time.toDouble, -distance.toDouble)
  val minimum = min.toInt + 1
  val maximum = if (max.toInt.toDouble == max) max.toInt - 1 else max.toInt
  maximum - minimum + 1

def solve6_1(inputs: Vector[String]): BigInt =
  val pairs: Vector[(Int, Int)] = inputs(0).split(" ").map(_.trim).filter(_.nonEmpty).tail.map(_.toInt).zip(inputs(1).split(" ").map(_.trim).filter(_.nonEmpty).tail.map(_.toInt)).toVector
  pairs.map { case (time, distance) =>
    answer(time, distance)
  }.product

def solve6_2(inputs: Vector[String]): BigInt =
  val time = BigInt(inputs(0).split(" ").map(_.trim).filter(_.nonEmpty).tail.mkString(""))
  val distance = BigInt(inputs(1).split(" ").map(_.trim).filter(_.nonEmpty).tail.mkString(""))
  answer(time, distance)

@main def solve6(): Unit =
  val in = new FileInputStream("example6-2.in")
  System.setIn(in)
  val inputs = Iterator.continually(StdIn.readLine())
    .takeWhile(line => null != line)
    .toVector

  println(solve6_1(inputs))
  println(solve6_2(inputs))