aoc_2024/day10.kts

#!/usr/bin/env kotlin
import java.util.Scanner


class TrailHead(private val x: Int, private val y: Int, private val map: Map) {
    private val peaks = mutableMapOf<Pair<Int, Int>, Int>()
    fun getScore(): Int {
        if (this.peaks.isEmpty()) {
            for (peak in this.walkToPeak(this.x, this.y)) {
                this.peaks[peak] = (this.peaks[peak] ?: 0) + 1
            }
        }
        return this.peaks.keys.size
    }
    fun getGetRating(): Int {
        this.getScore()
        return this.peaks.values.sum()
    }

    private fun walkToPeak(x: Int, y: Int, previous: Int = -1): List<Pair<Int, Int>> {
        if (x < 0 || x >= map.getLength() || y < 0 || y >= map.getHeight() || map.get(x, y) != (previous + 1)) {
            return listOf()
        } else if (map.get(x, y) == 9) {
            return listOf(Pair(x, y))
        } else {
            val current = map.get(x, y)
            return walkToPeak(x + 1, y, current) + walkToPeak(x - 1, y, current) + walkToPeak(x, y + 1, current) + walkToPeak(x, y - 1, current)
        }
    }

}

class Map(private val grid: List<List<Int>>) {
    private val trailHeads = mutableListOf<TrailHead>()

    init {
        grid.forEachIndexed { y, row ->
            row.forEachIndexed { x, height ->
                if (height == 0) {
                    trailHeads.add(TrailHead(x, y, this))
                }
            }
        }
    }

    fun addTrailHead(trailHead: TrailHead) {
        trailHeads.add(trailHead)
    }

    fun get(x: Int, y: Int): Int {
        return grid[y][x]
    }

    fun getHeight(): Int {
        return grid.size
    }

    fun getLength(): Int {
        return if (grid.isNotEmpty()) grid[0].size else 0
    }

    fun getScore(): Int {
        return trailHeads.fold(0) { acc, trailHead -> acc + trailHead.getScore() }
    }

    fun getGetRating(): Int {
        return trailHeads.fold(0) { acc, trailHead -> acc + trailHead.getGetRating() }
    }
}


val scanner = Scanner(System.`in`)
val mapInput = mutableListOf<List<Int>>()
while (scanner.hasNext()) {
    val line = scanner.nextLine()
    val numbers = line.split("").filter { it.isNotEmpty() }.map { it.toInt() }
    mapInput.add(numbers)
}
val map = Map(mapInput.reversed())

println("Score: ${map.getScore()}")
println("Rating: ${map.getGetRating()}")