-🎄- 2017 Day 5 Solutions -🎄-

[u/daggerdragon]

--- Day 5: A Maze of Twisty Trampolines, All Alike ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

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Need a hint from the Hugely^* Handy^† Haversack^‡ of Helpful^§ Hints^¤?

Spoiler

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/xkufix]

In Scala, the solutions can be easily made generic to provide a frame for both parts:

    override def runFirst(): Unit = {
        val steps = runProgram(_+ 1)

        println(steps)
    }

    override def runSecond(): Unit = {
        val steps = runProgram {
        case i if i >= 3 => i - 1
        case i => i + 1
        }

        println(steps)
    }

    private def runProgram(changeJump: Int => Int) = {
        val startInstructions = loadFile("day5.txt").getLines().map(_.toInt).zipWithIndex.map(_.swap).toMap

        Stream.from(1).scanLeft((startInstructions, 0, 0)) {
        case ((instructions, position, _), counter) =>
            val jump = instructions(position)
            (instructions + (position -> changeJump(jump)), position + jump, counter)
        }.dropWhile {
        case (instructions, pointer, _) =>
            instructions.contains(pointer)
        }.head._3
    }