AOC - 2024 day 18

package Y2024.D18

class RamFall(lines: List<String>, val width: Int, val height: Int) {
    val bytes = lines.map { it.split(",").map(String::toInt) }.map { it[1] to it[0] }

    fun runElvesRun(): Int? {
        return walkTheRam(bytes.take(1024))
    }

    fun whenAreWeBlocked(): String {
        var upperBound = bytes.size
        var lowerBound = 0
        while (lowerBound != upperBound) {
            val numberOfBytes = (lowerBound + upperBound) / 2
            if (walkTheRam(bytes.take(numberOfBytes)) == null) upperBound = numberOfBytes - 1
            else lowerBound = numberOfBytes
        }
        return "" + bytes[lowerBound].second + "," + bytes[lowerBound].first
    }

    private fun walkTheRam(fallenBytes: List<Pair<Int, Int>>): Int? {
        val nextPositions = mutableListOf(0 to 0)
        val visited = mutableMapOf((0 to 0) to 0)

        while (nextPositions.isNotEmpty()) {
            val pos = nextPositions.removeAt(0)
            val step = visited[pos]!!
            pos.findNeighbours()
                .filter { !fallenBytes.contains(it) }
                .filter { (visited[it] ?: Int.MAX_VALUE) > step + 1 }
                .forEach {
                    visited[it] = step + 1
                    nextPositions.add(it)
                }
        }
        return visited[height to width]
    }

    private fun Pair<Int, Int>.findNeighbours(): List<Pair<Int, Int>> {
        return listOf(
            this + (-1 to 0),
            this + (1 to 0),
            this + (0 to -1),
            this + (0 to 1)
        )
            .filter { it.first in 0..height && it.second in 0..width }
    }

    private operator fun Pair<Int, Int>.plus(other: Pair<Int, Int>): Pair<Int, Int> {
        return first + other.first to second + other.second
    }

    private fun printRam(fallenBytes: List<Pair<Int, Int>>, visited: MutableMap<Pair<Int, Int>, Int>) {
        println("Number of bytes: " + fallenBytes.size)
        repeat(height+1) {y ->
            repeat(width+1) { x ->
                if (fallenBytes.contains(y to x)) print("|")
                else if (visited.keys.contains(y to x)) print("O")
                else print(".")
            }
            println()
        }
    }
}