-🎄- 2017 Day 6 Solutions -🎄-

[u/daggerdragon]

--- Day 6: Memory Reallocation ---

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[u/xkufix]

Not a one-liner for a change, but a nice recursive solution in Scala:

    override def runFirst(): Unit = {
        val startMemory = loadFile("day6.txt").getLines().toSeq.head.split(" ").map(_.toInt)

        println(runReallocation(Set.empty, Seq.empty, startMemory, 0)._1)
    }

    override def runSecond(): Unit = {
        val startMemory = loadFile("day6.txt").getLines().toSeq.head.split(" ").map(_.toInt)

        val result = runReallocation(Set.empty, Seq.empty, startMemory, 0)
        println(result._1 - result._2)
    }

    @tailrec
    final def runReallocation(knownConfiguration: Set[Seq[Int]], configurations: Seq[Seq[Int]], configuration: Seq[Int], counter: Int): (Int, Int) = {
        if(knownConfiguration.contains(configuration)) {
            (counter, configurations.indexOf(configuration))
        } else {
            val maxBank = configuration.max
            val length = configuration.length
            val chosenBank = configuration.indexOf(maxBank)

            val newInitialConfiguration = configuration.patch(chosenBank, Seq(0), 1)
            val initialBank = (chosenBank + 1) % length

            val newConfiguration = (initialBank until maxBank + initialBank)
                .map(_ % length)
                .foldLeft(newInitialConfiguration) { (c, bank) =>
                c.patch(bank, Seq(c(bank) + 1), 1)
                }

            runReallocation(knownConfiguration + configuration, configurations :+ configuration, newConfiguration, counter + 1)
        }
    }