Day 3.

src/aoc2025/Day03.kt

@@ -0,0 +1,56 @@
+package aoc2025
+
+import println
+import readInput
+
+/*
+--- Day 3: Lobby ---
+https://adventofcode.com/2025/day/3
+*/
+fun main() {
+    val inlineTestInput = """
+987654321111111
+811111111111119
+234234234234278
+818181911112111
+"""
+
+    val powTenTable = generateSequence(1L) { it * 10L }.take(20).toList().toLongArray()
+
+    fun rec(i: String, si: Int, left: Int): Long {
+        for (dig in 9 downTo 1) {
+            val dp = i.indexOf('0' + dig, si)
+            if (dp >= 0) {
+                if (left == 0) {
+                    return dig.toLong()
+                } else {
+                    val lastDigits = rec(i, dp + 1, left - 1)
+                    if (lastDigits >= 0) return lastDigits + dig * powTenTable[left]
+                }
+            }
+        }
+        return -1L
+    }
+
+    fun part1(input: List<String>): Long {
+        return input.sumOf { rec(it, 0, 1) }
+    }
+
+    fun part2(input: List<String>): Long {
+        return input.sumOf { rec(it, 0, 11) }
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = inlineTestInput.trim().reader().readLines()
+    //val testInput = readInput("aoc2025/Day03_test")
+    val testInputPart1Result = part1(testInput)
+    println("Part 1 Test: $testInputPart1Result")
+    val testInputPart2Result = part2(testInput)
+    println("Part 2 Test: $testInputPart2Result")
+    check(testInputPart1Result == 357L)
+    check(testInputPart2Result == 3121910778619L)
+
+    val input = readInput("aoc2025/Day03")
+    part1(input).println()
+    part2(input).println()
+}

src/downloader/Downloader.kt

@@ -4,15 +4,19 @@ import com.mohamedrejeb.ksoup.html.parser.KsoupHtmlHandler
 import com.mohamedrejeb.ksoup.html.parser.KsoupHtmlParser
 import fuel.Fuel
 import fuel.method
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.runBlocking
 import java.io.FileNotFoundException
 import java.nio.charset.Charset
 import java.nio.file.Files
 import java.nio.file.Paths
 import java.time.LocalDate
+import java.time.LocalTime
 import java.time.Month
 import java.time.ZoneId
 import java.util.*
+import kotlin.time.Duration.Companion.minutes
+import kotlin.time.Duration.Companion.seconds
 
 fun main() {
     var cookie = "<insert your session cookie here or store in gradle.properties>"
@@ -42,7 +46,7 @@ class Downloader(val year: Int, val packageName: String, val sessionCookie: Stri
         if (!Files.exists(targetDir)) {
             Files.createDirectories(targetDir)
         }
-        val now = LocalDate.now(ZoneId.of("UTC-1"))
+        val now = LocalDate.now(ZoneId.of("UTC+1"))
         val maxPuzzles = if (year < 2025) 25 else 12
         val lastDay = if (now.isBefore(LocalDate.of(year, Month.DECEMBER, maxPuzzles))) {
             if (now.isAfter(LocalDate.of(year, Month.NOVEMBER, 30))) {
@@ -60,6 +64,20 @@ class Downloader(val year: Int, val packageName: String, val sessionCookie: Stri
             val descriptionFile = targetDir.resolve(DESC_FILENAME.format(day))
             val genClassFile = targetDir.resolve(GENCLASS_FILENAME.format(day))
             if (!Files.exists(inputFile)) {
+                if (day == lastDay && LocalTime.now(ZoneId.of("UTC+1")).hour < 5) {
+                    println("Puzzle will not be available within the next hour. Skipping.")
+                    break
+                }
+                while (day == lastDay && LocalTime.now(ZoneId.of("UTC+1")).hour == 5) {
+                    println("Waiting until puzzle is available...")
+                    runBlocking {
+                        if (LocalTime.now(ZoneId.of("UTC+1")).minute < 59) {
+                            delay(1.minutes)
+                        } else {
+                            delay(1.seconds)
+                        }
+                    }
+                }
                 println("Attempting to download input for day $day")
                 val (code, data) = downloadInput(day)
                 if (code != 200) {
@@ -157,7 +175,7 @@ class Downloader(val year: Int, val packageName: String, val sessionCookie: Stri
                 url = "https://adventofcode.com/$year/day/$day$suffix",
                 method = "GET",
                 headers = mapOf(
-                    "User-Agent" to "git.platon42.de/chrisly42/advent-of-code",
+                    "User-Agent" to "git.platon42.de/chrisly42/advent-of-code (chrisly@platon42.de)",
                     "Cookie" to "session=$sessionCookie"
                 )
             )