Aoc2021_Day14.scala

package aoc2021

import java.util
import scala.annotation.tailrec
import scala.collection.mutable

object Day14:
  type InputType = (Seq[Char], Instruction)
  type Instruction = Map[(Char, Char), Char]

  @main def runDay14: Unit =
    val testData = time("testReady", () => ready(testInput))
    time("testPart1", () => part1(testData)) // should be 1588
    time("testPart2", () => part2(testData)) // should be 2188189693529

    val data = time("ready", () => ready(input))
    time("part1", () => part1(data))
    //time("part2", () => part2(data))

  def ready(input: String): InputType =
    val data = input
      .split("\n\n")
    (
      data(0)
        .toIndexedSeq,
      data(1)
        .linesIterator
        .map(_ match
          case s"$p -> $i" => ((p.head, p.last), i.head)
        )
        .toMap
    )

  def step(polymer: Seq[Char], instruction: Instruction): Seq[Char] =
    polymer.sliding(2)
      .flatMap(w => Seq(w.head, instruction.getOrElse((w.head, w.last), ' ')))
      .toSeq
      :+ polymer.last

  def part1(data: InputType): BigInt =
    val map = Range.apply(0, 10)
      .foldLeft(data._1)((p, _) => step(p, data._2))
      .groupBy(c => c)
      .map((k, v) => (k, v.size))
      .map((k, v) => v)
    map.max - map.min

  val cMap: mutable.HashMap[Char, Long] = mutable.HashMap.empty

  def inc(char: Char) =
    val count = cMap.getOrElse(char, 0L)
    cMap.put(char, count + 1)

  def step2(first: Char, second: Char, step: Int, maxStep: Int, inst: Instruction): Unit =
    if (step < maxStep) {
      val insertion = inst.getOrElse((first, second), ' ')
      inc(insertion)
      val nextStep = step + 1
      step2(first, insertion, nextStep, maxStep, inst)
      step2(insertion, second, nextStep, maxStep, inst)
    }

  def part2(data: InputType): BigInt =
    step2('N', 'N', 0, 10, data._2)
    println(cMap)
    0

  val testInput =
    """NNCB
      |
      |CH -> B
      |HH -> N
      |CB -> H
      |NH -> C
      |HB -> C
      |HC -> B
      |HN -> C
      |NN -> C
      |BH -> H
      |NC -> B
      |NB -> B
      |BN -> B
      |BB -> N
      |BC -> B
      |CC -> N
      |CN -> C""".stripMargin

  val input =
    """PBFNVFFPCPCPFPHKBONB
      |
      |KK -> S
      |FO -> B
      |PP -> O
      |HN -> S
      |CN -> H
      |VH -> P
      |BK -> B
      |VC -> N
      |CB -> H
      |OC -> K
      |BF -> P
      |FV -> K
      |SP -> F
      |OP -> K
      |SS -> B
      |NN -> O
      |CS -> K
      |CF -> K
      |FF -> S
      |SV -> P
      |OK -> S
      |CO -> F
      |OB -> K
      |BH -> B
      |HH -> S
      |VB -> V
      |KV -> H
      |CK -> V
      |NV -> N
      |SF -> V
      |PK -> H
      |PV -> N
      |FB -> O
      |BO -> K
      |FP -> N
      |OF -> N
      |FK -> O
      |VK -> V
      |NO -> V
      |NS -> C
      |KC -> S
      |VF -> V
      |BV -> N
      |CP -> K
      |PB -> V
      |CC -> S
      |NH -> B
      |CV -> P
      |SO -> V
      |NC -> O
      |HK -> K
      |SB -> H
      |OO -> V
      |HO -> P
      |PS -> B
      |BC -> P
      |KO -> C
      |KB -> C
      |VV -> F
      |BS -> F
      |HB -> B
      |KN -> S
      |FC -> C
      |SN -> S
      |HC -> O
      |HP -> F
      |BP -> V
      |ON -> K
      |BB -> K
      |KH -> O
      |NP -> H
      |KS -> N
      |SH -> K
      |VP -> O
      |PF -> O
      |HF -> S
      |BN -> S
      |NK -> C
      |FH -> O
      |CH -> B
      |KP -> B
      |FN -> K
      |OV -> P
      |VS -> K
      |OH -> V
      |PC -> F
      |VO -> H
      |SK -> S
      |PO -> O
      |KF -> N
      |NF -> V
      |NB -> C
      |PN -> O
      |FS -> C
      |PH -> F
      |VN -> S
      |OS -> V
      |HV -> H
      |HS -> B
      |SC -> C""".stripMargin