Day 2: Red-Nosed Reports
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Kotlin
A bit late to the party, but here you go.
import kotlin.math.abs
fun part1(input: String): Int {
return solve(input, ::isSafe)
}
fun part2(input: String): Int {
return solve(input, ::isDampSafe)
}
private fun solve(input: String, condition: (List<Int>) -> Boolean): Int {
var safeCount = 0
input.lines().forEach { line ->
if (line.isNotBlank()) {
val nums = line.split("\\s+".toRegex()).map { it.toInt() }
safeCount += if (condition(nums)) 1 else 0
}
}
return safeCount
}
private fun isSafe(list: List<Int>): Boolean {
val safeDiffs = setOf(1, 2, 3)
var incCount = 0
var decCount = 0
for (idx in 0..<list.lastIndex) {
if (!safeDiffs.contains(abs(list[idx] - list[idx + 1]))) {
return false
}
if (list[idx] <= list[idx + 1]) incCount++
if (list[idx] >= list[idx + 1]) decCount++
}
return incCount == 0 || decCount == 0
}
private fun isDampSafe(list: List<Int>): Boolean {
if (isSafe(list)) {
return true
} else {
for (idx in 0..list.lastIndex) {
val shortened = list.toMutableList()
shortened.removeAt(idx)
if (isSafe(shortened)) {
return true
}
}
}
return false
}