advent.of.code.day.14

advent.of.code.day.14.scala

package day14

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

@main def solve14_1() =
  def masking(bit: String, mask: String): Double = {
    mask.zipWithIndex.foldLeft(0.0)((acc, maskNext) => {
      val maskVal = maskNext._1
      val index = maskNext._2
      if (bit.length > index) {
        mask.charAt(index) match {
          case 'X' =>
            val value = if bit.charAt(index) == '1' then Math.pow(2, mask.length - index - 1) else 0.0
            acc + value
          case maskVal: Char =>
            val value = if maskVal == '1' then Math.pow(2, mask.length - index - 1) else 0.0
            acc + value
        }
      } else {
        val value = if maskVal == '1' then Math.pow(2, mask.length - index - 1) else 0.0
        acc + value
      } 
    })
  }

  def solve(list: List[String], map: Map[Int, Long], mask: String): Map[Int, Long] = {
    list match {
      case Nil => map
      case _ =>
        val head = list.head
        if head.startsWith("mask") then solve(list.tail, map, head.substring(7))
        else {
          val idx = head.substring(head.indexOf("[") + 1, head.indexOf("]")).toInt
          val bit = head.substring(head.indexOf("=") + 2).toLong.toBinaryString
          solve(list.tail, map + (idx -> masking(bit, mask).toLong), mask)
        }
    }
  }

  val in = new FileInputStream("src/example14-1.in")
  System.setIn(in)
  val inputs = Iterator.continually(StdIn.readLine()).takeWhile(_ != null).toList
  println(solve(inputs, Map.empty[Int, Long], "").foldLeft(0L)((a, b) => a + b._2))