111 lines
3.6 KiB
Kotlin
111 lines
3.6 KiB
Kotlin
package aoc.thirteen
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import aoc.thirteen.Field
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import aoc.thirteen.Turn
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import aoc.thirteen.Train
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import java.io.File
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import java.io.InputStream
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class Main() {
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companion object {
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public var field: MutableList<MutableList<Field>> = mutableListOf<MutableList<Field>>()
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fun parseField(c: Char): Field {
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return when (c) {
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'|', 'v', '^' -> Field.VERTICAL
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'-', '>', '<' -> Field.HORIZONTAL
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'/' -> Field.TOP_LEFT
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'\\' -> Field.TOP_RIGHT
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'+' -> Field.INTERSECTION
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' ' -> Field.EMPTY
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else -> throw IllegalArgumentException("can’t parse field " + c)
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}
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}
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fun cleanUpAfterCrash(trains: MutableList<Train>): Pair<Int, Int> {
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for ((i, train) in trains.withIndex()) {
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for ((j, t2) in trains.withIndex()) {
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if (train != t2 && train.x == t2.x && train.y == t2.y) {
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return Pair(i, j)
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}
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}
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}
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return Pair(-1, -1)
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}
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fun parseTrain(c: Char, x: Int, y: Int): Train {
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val dir = when (c) {
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'^' -> 0
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'>' -> 1
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'v' -> 2
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'<' -> 3
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else -> throw IllegalArgumentException("this shouldn’t happen rooDerp")
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}
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return Train(dir, x, y)
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}
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fun moveTrain(t: Train): Train {
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when (t.direction) {
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0 -> t.y -= 1
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1 -> t.x += 1
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2 -> t.y += 1
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3 -> t.x -= 1
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else -> throw IllegalArgumentException("this shouldn’t happen either selphyDerp")
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}
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val current = field[t.y][t.x]
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when (current) {
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Field.VERTICAL, Field.HORIZONTAL -> {}
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Field.TOP_LEFT -> t.direction = t.direction xor 1
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Field.TOP_RIGHT -> t.direction = t.direction xor 3
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Field.INTERSECTION -> t.crossIntersection()
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Field.EMPTY -> throw IllegalStateException("I shouldn’t be here")
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}
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return t
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}
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@JvmStatic
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fun main(args: Array<String>) {
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val inputStream = File("input").inputStream()
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val inputLines = inputStream.bufferedReader().use { it.readText() }.split("\n")
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val TRAINS = charArrayOf('<', '>', '^', 'v')
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var trains = mutableListOf<Train>()
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for ((y, line) in inputLines.withIndex()) {
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var fields = mutableListOf<Field>()
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for ((x, char) in line.toCharArray().withIndex()) {
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if (char in TRAINS) {
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val newTrain = parseTrain(char, x, y)
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trains.add(newTrain)
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}
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fields.add(parseField(char))
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}
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field.add(fields)
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}
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var positions = HashSet<Pair<Int, Int>>(trains.size)
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positions.addAll(trains.map{ t -> Pair(t.x, t.y) })
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var crash = false
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var remove = Pair(-1, -1)
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while (trains.size > 1) {
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for ((i, train) in trains.withIndex()) {
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trains[i] = moveTrain(train)
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positions.clear()
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positions.addAll(trains.map{ t -> Pair(t.x, t.y) })
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// This is not ideal, but there is never more than one crash per tick
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if (trains.size > positions.size && !crash) {
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remove = cleanUpAfterCrash(trains)
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crash = true
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}
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}
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if (crash) {
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trains.removeAll(listOf(trains[remove.first], trains[remove.second]))
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crash = false
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}
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trains = trains.sortedBy{ it.y * 200 + it.x }.toMutableList()
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}
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println("${trains[0].x},${trains[0].y}")
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}
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}
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}
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