Advent of Code 05 part 1.scala

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

@main def solve5() =
  def solve(seatNumber: String): Int = {
    case class Range(min: Int, max: Int)
    def partitioning(ch: Char, range: Range): Range = {
      if ch == 'F' || ch == 'L' then
        Range(range.min, range.min + (range.max - range.min) / 2)
      else
        Range(range.max - (range.max - range.min) / 2, range.max)
    }

    val row = seatNumber.take(7).foldLeft(Range(0, 127)) { (acc, ch) => partitioning(ch, acc) }.min
    val col = seatNumber.drop(7).foldLeft(Range(0, 7)) { (acc, ch) => partitioning(ch, acc) }.min
    row * 8 + col
  }

  val in = new FileInputStream("example5-1.in")
  System.setIn(in)

  val inputs = Iterator.continually(StdIn.readLine()).takeWhile(_ != null).toVector
  println(inputs.map { solve }.max)

Advent of Code 05 part 2.scala

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

@main def solve5() =
  def solve(seatNumber: String): Int = {
    case class Range(min: Int, max: Int)
    def partitioning(ch: Char, range: Range): Range = {
      if ch == 'F' || ch == 'L' then
        Range(range.min, range.min + (range.max - range.min) / 2)
      else
        Range(range.max - (range.max - range.min) / 2, range.max)
    }

    val row = seatNumber.take(7).foldLeft(Range(0, 127)) { (acc, ch) => partitioning(ch, acc) }.min
    val col = seatNumber.drop(7).foldLeft(Range(0, 7)) { (acc, ch) => partitioning(ch, acc) }.min
    row * 8 + col
  }

  val in = new FileInputStream("example5-1.in")
  System.setIn(in)

  val inputs = Iterator.continually(StdIn.readLine()).takeWhile(_ != null).toVector
  val ids = inputs.map { solve }.sorted
  val emptyIdx = ids.indices.tail.find(idx => ids(idx - 1) + 1 != ids(idx)).getOrElse(0)
  println(ids(emptyIdx - 1) + 1)