2025 Day 02 WIP

Author: fibsifan

src/main/kotlin/de/jball/aoc2025/day02/Day02.kt

@@ -2,22 +2,46 @@ package de.jball.aoc2025.day02
 
 import de.jball.AdventOfCodeDay
 
-class Day02(test: Boolean = false): AdventOfCodeDay<Long>(test, 1227775554L, 0L) {
-	val ranges = input[0].split(",").map { rangeString ->
-		val rangeNums = rangeString.split("-")
-			.map { numberString -> numberString.toLong() }
-		rangeNums[0]..rangeNums[1]
+class Day02(test: Boolean = false): AdventOfCodeDay<Long>(test, 1227775554L, 4174379265L) {
+	val ranges = input[0]
+		.split(",")
+		.map { rangeString ->
+			val rangeNums = rangeString.split("-")
+				.map { numberString -> numberString.toLong() }
+			rangeNums[0]..rangeNums[1]
 	}
 
 	override fun part1(): Long {
-		ranges.map { range ->
-			range.map { it.toString() }
+		return ranges.sumOf { range ->
+			sumOfInvalidIds(range, { idString ->
+				val windowSize = idString.length / 2 + idString.length % 2
+				windowSize..windowSize
+			})
 		}
-		TODO("Not yet implemented")
+	}
+
+	private fun sumOfInvalidIds(range: LongRange, windowFunction: (id: String) -> IntRange): Long = range.map { number ->
+		number.toString()
+	}.filter { idString ->
+		windowFunction(idString)
+			.any { windowSize ->
+				// if the different parts of the id string are all equal, then the distinct call would result in a list of size 1.
+				idString.windowed(windowSize, windowSize, true).distinct().size == 1
+			}
+	}.sumOf { numberString ->
+		numberString.toLong()
 	}
 
 	override fun part2(): Long {
-		TODO("Not yet implemented")
+		return ranges.sumOf { range ->
+			sumOfInvalidIds(range, { idString ->
+				1..(idString.length / 2 + idString.length % 2)
+			})
+		}
 	}
 
 }
+
+fun main() {
+	Day02().run()
+}