Day 11 complete.

src/main/kotlin/common/aocreader/aocreader.kt

@@ -1,3 +1,6 @@
+// Advent of Code 2024
+// By Sebastian Raaphorst, 2024.
+
 package common.aocreader
 
 import java.net.HttpURLConnection

src/main/kotlin/common/collectionops/collectionops.kt

@@ -1,4 +1,4 @@
-// Advent of Code
+// Advent of Code 2024
 // By Sebastian Raaphorst, 2024.
 
 package common.collectionops

src/main/kotlin/common/intpos2d/intpos2d.kt

@@ -1,3 +1,6 @@
+// Advent of Code 2024
+// By Sebastian Raaphorst, 2024.
+
 package common.intpos2d
 
 typealias IntPos2D = Pair<Int, Int>

src/main/kotlin/common/parsing/parsing.kt

@@ -1,4 +1,4 @@
-// Advent of Code
+// Advent of Code 2024
 // By Sebastian Raaphorst, 2024.
 
 package common.parsing

src/main/kotlin/common/runner/timed.kt

@@ -0,0 +1,12 @@
+// Advent of Code 2024
+// By Sebastian Raaphorst, 2024.
+
+package common.runner
+
+inline fun <T> timedFunction(functionName: String, block: () -> T): T {
+    val startTime = System.nanoTime()
+    val result = block()
+    val endTime = System.nanoTime()
+    println("$functionName: $result (${(endTime - startTime) / 1_000_000.0} ms)")
+    return result
+}

src/main/kotlin/common/stringops.kt

@@ -1,4 +1,4 @@
-// Advent of Code
+// Advent of Code 2024
 // By Sebastian Raaphorst, 2024.
 
 package common

src/main/kotlin/day01/day01.kt

@@ -6,6 +6,7 @@ package day01
 import common.aocreader.fetchAdventOfCodeInput
 import common.parsing.parseColumns
 import common.collectionops.toFrequencyMap
+import common.runner.timedFunction
 import kotlin.math.abs
 
 fun answer1(input: String): Int =
@@ -25,12 +26,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 1)
-
     println("--- Day 1: Historian Hysteria ---")
-
-    // Answer 1: 2031679
-    println("Part 1: ${answer1(input)}")
-
-    // Answer 2: 19678534
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 2031679
+    timedFunction("Part 2") { answer2(input) } // 19678534
 }

src/main/kotlin/day02/day02.kt

@@ -6,6 +6,7 @@ package day02
 import common.aocreader.fetchAdventOfCodeInput
 import common.collectionops.allListDrops
 import common.parsing.parseGrid
+import common.runner.timedFunction
 
 private const val Lower = 1
 private const val Upper = 3
@@ -30,12 +31,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 2)
-
     println("--- Day 2: Red-Nosed Reports ---")
-
-    // Answer 1: 379
-    println("Part 1: ${answer1(input)}")
-
-    // Answer 2: 430
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 379
+    timedFunction("Part 2") { answer2(input) } // 430
 }

src/main/kotlin/day03/day03.kt

@@ -4,6 +4,7 @@
 package day03
 
 import common.aocreader.fetchAdventOfCodeInput
+import common.runner.timedFunction
 
 /**
  * We want to turn off processing for substrings of the form:
@@ -31,12 +32,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 3)
-
     println("--- Day 3: Mull It Over ---")
-
-    // Answer 1: 173785482
-    println("Part 1: ${answer1(input)}")
-
-    // Answer 2: 83158140
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 173785482
+    timedFunction("Part 2") { answer2(input) } // 83158140
 }

src/main/kotlin/day04/day04.kt

@@ -6,6 +6,7 @@ package day04
 import common.aocreader.fetchAdventOfCodeInput
 import common.countSubstrings
 import common.collectionops.*
+import common.runner.timedFunction
 
 private const val XMAS = "XMAS"
 
@@ -60,12 +61,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 4)
-
     println("--- Day 4: Ceres Search ---")
-
-    // Answer 1: 2370
-    println("Part 1: ${answer1(input)}")
-
-    // Answer 2: 1908
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 2370
+    timedFunction("Part 2") { answer2(input) } // 1908
 }

src/main/kotlin/day05/day05.kt

@@ -5,6 +5,7 @@ package day05
 
 import common.aocreader.fetchAdventOfCodeInput
 import common.collectionops.middle
+import common.runner.timedFunction
 
 private typealias OrderingRules = Map<Int, Set<Int>>
 private typealias Updates = List<Int>
@@ -96,12 +97,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 5)
-
     println("--- Day 5: Print Queue ---")
-
-    // Part 1: 4281
-    println("Part 1: ${answer1(input)}")
-
-    // Part 2: 5466
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 4281
+    timedFunction("Part 2") { answer2(input) } // 5466
 }

src/main/kotlin/day06/day06.kt

@@ -1,13 +1,11 @@
 // Advent of Code 2024, Day 06.
 // By Sebastian Raaphorst, 2024.
 
-// NOTE: Trying to use pure FP in this question made part 2 run extremely slowly.
-// Mutable data structures are needed to avoid having to continuously copy structures.
-
 package day06
 
 import common.aocreader.fetchAdventOfCodeInput
 import common.intpos2d.*
+import common.runner.timedFunction
 
 private typealias Orientation = Pair<Direction, IntPos2D>
 
@@ -84,12 +82,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 6)
-
     println("--- Day 6: Guard Gallivant ---")
-
-    // Part 1: 5208
-    println("Part 1: ${answer1(input)}")
-
-    // Part 2: 1972
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 5208
+    timedFunction("Part 2") { answer2(input) } // 1972
 }

src/main/kotlin/day07/day07.kt

@@ -4,9 +4,8 @@
 package day07
 
 import common.aocreader.fetchAdventOfCodeInput
-import common.day
 import common.parsing.WhitespaceParser
-import common.readInput
+import common.runner.timedFunction
 import java.math.BigInteger
 
 data class Equation(val total: BigInteger, val numbers: List<BigInteger>) {
@@ -61,12 +60,7 @@ fun answer2(input: String): BigInteger =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 7)
-
     println("--- Day 7: Bridge Repair ---")
-
-    // Part 1: 2437272016585
-    println("Part 1: ${answer1(input)}")
-
-    // Part 2: 162987117690649
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 2437272016585
+    timedFunction("Part 2") { answer2(input) } // 162987117690649
 }

src/main/kotlin/day08/day08.kt

@@ -5,6 +5,7 @@ package day08
 
 import common.aocreader.fetchAdventOfCodeInput
 import common.intpos2d.*
+import common.runner.timedFunction
 
 private typealias Frequency = Char
 private typealias AntennaMap = Map<Frequency, Set<IntPos2D>>
@@ -83,12 +84,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 8)
-
     println("--- Day 8: Resonant Collinearity ---")
-
-    // Part 1: 376
-    println("Part 1: ${answer1(input)}")
-
-    // Part 2: 1352
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 376
+    timedFunction("Part 2") { answer2(input) } // 1352
 }

src/main/kotlin/day09/day09.kt

@@ -4,6 +4,7 @@
 package day09
 
 import common.aocreader.fetchAdventOfCodeInput
+import common.runner.timedFunction
 import java.math.BigInteger
 
 private typealias Range = LongRange
@@ -190,12 +191,7 @@ fun answer2(input: String): BigInteger =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 9)
-
     println("--- Day 9: Disk Fragmenter ---")
-
-    // Part 1: 6384282079460
-    println("Part 1: ${answer1(input)}")
-
-    // Part 2: 6408966547049
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 6384282079460
+    timedFunction("Part 2") { answer2(input) } // 6408966547049
 }

src/main/kotlin/day10/day10.kt

@@ -1,10 +1,11 @@
-// Advent of Code 2024, Day 09.
+// Advent of Code 2024, Day 10.
 // By Sebastian Raaphorst, 2024.
 
 package day10
 
 import common.aocreader.fetchAdventOfCodeInput
 import common.intpos2d.*
+import common.runner.timedFunction
 
 private typealias Trail = List<IntPos2D>
 private typealias Trails = Set<List<IntPos2D>>
@@ -57,12 +58,7 @@ fun answer2(input: String): Int =
 
 fun main() {
     val input = fetchAdventOfCodeInput(2024, 10)
-
     println("--- Day 10: Hoof It ---")
-
-    // Part 1: 719
-    println("Part 1: ${answer1(input)}")
-
-    // Part 2: 1530
-    println("Part 2: ${answer2(input)}")
+    timedFunction("Part 1") { answer1(input) } // 719
+    timedFunction("Part 2") { answer2(input) } // 1530
 }

src/main/kotlin/day11/day11.kt

@@ -0,0 +1,66 @@
+// Advent of Code 2024, Day 11.
+// By Sebastian Raaphorst, 2024.
+
+package day11
+
+import common.aocreader.fetchAdventOfCodeInput
+import common.parsing.WhitespaceParser
+import common.runner.timedFunction
+import day11.StoneRules.cacheSize
+import java.util.concurrent.ConcurrentHashMap
+
+
+private fun parse(input: String): MutableMap<Long, Long> =
+    input.split(WhitespaceParser)
+        .map(String::toLong)
+        .groupingBy { it }
+        .eachCount()
+        .mapValues { it.value.toLong() }
+        .toMutableMap()
+
+// The key is that the order of the stones have no relevance.
+private object StoneRules {
+    private val memoization: MutableMap<Long, List<Long>> = ConcurrentHashMap()
+
+    private fun rule(stone: Long): List<Long> = memoization.computeIfAbsent(stone) {
+        when {
+            it == 0L -> listOf(1L)
+            it.toString().length % 2 == 0 -> {
+                val middle = it.toString().length / 2
+                listOf(
+                    it.toString().substring(0, middle).toLong(),
+                    it.toString().substring(middle).toLong()
+                )
+            }
+            else -> listOf(it * 2024)
+        }
+    }
+
+    fun blink(stones: Map<Long, Long>): MutableMap<Long, Long> =
+        stones.flatMap { (stone, count) ->
+            rule(stone).map { transformed -> transformed to count }
+        }.groupingBy { it.first }
+            .fold(0L) { acc, (_, count) -> acc + count }
+            .toMutableMap()
+
+    fun cacheSize(): Int = memoization.size
+}
+
+private fun answer(input: String, blinks: Int): Long =
+    (1..blinks).fold(parse(input)) { stones, _ -> StoneRules.blink(stones) }
+        .values.sum()
+
+fun answer1(input: String): Long =
+    answer(input, 25)
+
+fun answer2(input: String): Long =
+    answer(input, 75)
+
+fun main() {
+    val input = fetchAdventOfCodeInput(2024, 11)
+    println("--- Day 11: Plutonian Pebbles ---")
+    timedFunction("Part 1") { answer1(input) }
+    println("\tCache size: ${cacheSize()}")
+    timedFunction("Part 2") { answer2(input) }
+    println("\tCache size: ${cacheSize()}")
+}

src/test/kotlin/day04/day04.kt

@@ -21,7 +21,6 @@ class Day04Test {
             MAMMMXMMMM
             MXMXAXMASX
             """.trimIndent()
-
     }
 
     @Test

src/test/kotlin/day11/day11.kt

@@ -0,0 +1,21 @@
+// Advent of Code 2024, Day 11.
+// By Sebastian Raaphorst, 2024.
+
+package day11
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+// Note: no problem 2 test today.
+class Day11Test {
+    private companion object {
+        val input =
+            """
+            125 17
+            """.trimIndent().trim()
+    }
+
+    @Test
+    fun `Problem 1 example`() =
+        assertEquals(55312L, answer1(input))
+}