advent-of-code-2024/06-a.kts

import java.util.Scanner

enum class Direction {
    NORTH {
        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
            return Pair(row-1, col)
        }
    }, SOUTH {
        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
            return Pair(row+1, col)
        }
    }, WEST {
        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
            return Pair(row, col-1)
        }
    }, EAST {
        override fun moveFrom(row: Int, col: Int): Pair<Int, Int> {
            return Pair(row, col+1)
        }
    };

    fun turnRight(): Direction {
        return when (this) {
            NORTH -> EAST
            EAST -> SOUTH
            SOUTH -> WEST
            WEST -> NORTH
        }
    }

    abstract fun moveFrom(row: Int, col: Int): Pair<Int, Int>
}

val scanner = Scanner(System.`in`)

val map = ArrayList<Array<Char>>()

var rows = 0
var guardRow = -1
var guardCol = -1
while (scanner.hasNextLine()) {
    val line = scanner.nextLine()
    val pos = line.indexOf('^')
    if (pos != -1) {
        guardRow = rows
        guardCol = pos
    }
    val chars = line.toCharArray().toTypedArray()
    map.add(chars)
    rows++
}

var facing = Direction.NORTH

var visitedCount = 0
walk@ while (true) {
    if (map[guardRow][guardCol] != 'X') {
        visitedCount++
    }
    map[guardRow][guardCol] = 'X'

    var seeking = true
    do {
        val (nextRow, nextCol) = facing.moveFrom(guardRow, guardCol)
        if (nextRow < 0 || nextRow >= map.size || nextCol < 0 || nextCol >= map[nextCol].size) {
            break@walk
        }

        if (map[nextRow][nextCol] == '#') {
            facing = facing.turnRight()
        } else {
            guardRow = nextRow
            guardCol = nextCol
            seeking = false
        }
    } while (seeking)
}
println(visitedCount)