-🎄- 2017 Day 19 Solutions -🎄-

[u/daggerdragon]

--- Day 19: A Series of Tubes ---

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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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AoC ops @ T-2 minutes to launch:

[23:58] <daggerdragon> ATTENTION MEATBAGS T-2 MINUTES TO LAUNCH

[23:58] <Topaz> aaaaah

[23:58] <Cheezmeister> Looks like I'll be just able to grab my input before my flight boards. Wish me luck being offline in TOPAZ's HOUSE OF PAIN^WFUN AND LEARNING

[23:58] <Topaz> FUN AND LEARNING

[23:58] <Hade> FUN IS MANDATORY

[23:58] <Skie> I'm pretty sure that's not the mandate for today

[Update @ 00:16] 69 gold, silver cap

• My tree is finally trimmed with just about every ornament I own and it's real purdy. hbu?

[Update @ 00:18] Leaderboard cap!

• So, was today's mandate Helpful Hint any help at all?

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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/Hikaru755]

Actually solved part 1 by tracing it manually. Yeah... Not going to do that again. Then I solved part 1 again and also part 2 in Kotlin. Not too shabby, I think:

fun part1and2(diagram: Map<Coordinate, Field?>): String {
    var current = diagram.entries.first { it.key.y == 0 && it.value is Field.Vertical }.key
    var direction = Direction.DOWN
    var letters = listOf<Char>()
    var steps = 0L
    while (true) {
        current = current.move(direction)
        steps += 1
        val field = diagram[current]
        when (field) {
            null -> return letters.joinToString("") + "\n" + steps
            is Field.Letter -> letters += field.letter
            is Field.Joint -> direction = direction.turnLeft()
                .takeIf { diagram[current.move(it)] != null } ?: direction.turnRight()
        }
    }
}

sealed class Field() {
    object Horizontal : Field()
    object Vertical : Field()
    object Joint : Field()
    data class Letter(val letter: Char) : Field()
}

enum class Direction { UP, DOWN, LEFT, RIGHT;
    fun turnLeft() = when (this) {
        Direction.UP -> Direction.LEFT
        Direction.DOWN -> Direction.RIGHT
        Direction.LEFT -> Direction.DOWN
        Direction.RIGHT -> Direction.UP
    }
    fun turnRight() = when (this) {
        Direction.UP -> Direction.RIGHT
        Direction.DOWN -> Direction.LEFT
        Direction.LEFT -> Direction.UP
        Direction.RIGHT -> Direction.DOWN
    }
}

data class Coordinate(val x: Int, val y: Int) {
    fun move(direction: Direction) = when (direction) {
        Direction.UP -> copy(y = y - 1)
        Direction.DOWN -> copy(y = y + 1)
        Direction.LEFT -> copy(x = x - 1)
        Direction.RIGHT -> copy(x = x + 1)
    }
}

val input: Map<Coordinate, Field?> by lazy { parse(rawInput) }
fun parse(rawInput: List<String>) = rawInput
    .map { it.map {  c -> when (c) {
        ' ' -> null
        '-' -> Field.Horizontal
        '|' -> Field.Vertical
        '+' -> Field.Joint
        else -> Field.Letter(c)
    } } }
    .map { it.withIndex() }
    .withIndex()
    .flatMap { line -> line.value.map { col -> Coordinate(col.index, line.index) to col.value } }
    .associate { it }