advent-of-code/13/main_2.kt

111 lines
3.6 KiB
Kotlin

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