aoc_2024/day02.kts

import java.io.File
import java.util.Scanner
import kotlin.math.abs

val scanner = Scanner(File("day02input.txt"))
var safelines = 0
var dampenedsafelines = 0
while (scanner.hasNextLine()) {
    val line = scanner.nextLine()
    val numbers = line.split(" ").map { it.toInt() }
    if (isSafe(numbers)) {
        safelines++
    } else if (dampenedSafe(numbers)) {
        dampenedsafelines++
    }
}
println("Safe lines: $safelines")
println("Safe lines with dampener: ${dampenedsafelines + safelines}")

fun isSafe(numbers: List<Int> ): Boolean {
    var directionality = 0
    for (i in 1 until numbers.size) {
        val direction = if (numbers[i] > numbers[i - 1]) 1 else -1
        if (directionality == 0) {
            directionality = direction
        } else if (directionality != direction) {
            return false
        }
        val difference = abs(numbers[i] - numbers[i - 1])
        if (difference < 1 || difference > 3) {
            return false
        }
    }
    return true
}

fun dampenedSafe(numbers: List<Int>): Boolean {
    // Brute force approach
    for (i in numbers.indices) {
        val copy = numbers.toMutableList()
        copy.removeAt(i)
        if (isSafe(copy)) {
            return true
        }
    }
    return false
}