[2024/25] Code Chronicle (Part 1)

README.md

@@ -28,7 +28,7 @@
 |     2021 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |        |   ★    |   ★    |        |        |        |        |        |        |        |        |        |        |        |    26 |
 |     2022 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |        |        |        |        |        |        |        |   ☆    |        |        |        |   ☆    |    28 |
 |     2023 |   ★   |   ★   |   ★   |   ★   |   ☆   |   ★   |   ☆   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    12 |
-|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |   ★    |        |   ☆    |   ★    |   ★    |   ★    |   ★    |        |   ★    |        |        |        |    39 |
+|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |   ★    |        |   ☆    |   ★    |   ★    |   ★    |   ★    |        |   ★    |        |        |   ☆    |    40 |
 
 ## 🛷 How to run
 
@@ -184,6 +184,7 @@ e.g. `HandyHaversacks`)*
 |                                           |  19 | [Linen Layout](https://adventofcode.com/2024/day/19)                                                   | [[Code](src/main/kotlin/adventofcode/year2024/Day19LinenLayout.kt)] [[Test](src/test/kotlin/adventofcode/year2024/Day19LinenLayoutSpec.kt)]                                             | `267`                  | `796449099271652`                                |
 |                                           |  20 | [Race Condition](https://adventofcode.com/2024/day/20)                                                 | [[Code](src/main/kotlin/adventofcode/year2024/Day20RaceCondition.kt)] [[Test](src/test/kotlin/adventofcode/year2024/Day20RaceConditionSpec.kt)]                                         | `1426`                 | `1000697`                                        |
 |                                           |  22 | [Monkey Market](https://adventofcode.com/2024/day/22)                                                  | [[Code](src/main/kotlin/adventofcode/year2024/Day22MonkeyMarket.kt)] [[Test](src/test/kotlin/adventofcode/year2024/Day22MonkeyMarketSpec.kt)]                                           | `20332089158`          | `2191`                                           |
+|                                           |  25 | [Code Chronicle](https://adventofcode.com/2024/day/25)                                                 | [[Code](src/main/kotlin/adventofcode/year2024/Day25CodeChronicle.kt)] [[Test](src/test/kotlin/adventofcode/year2024/Day25CodeChronicleSpec.kt)]                                         | `3608`                 |                                                  |
 
 ## 🕯️ Useful commands
 

src/main/kotlin/adventofcode/common/spatial/Grid2d.kt

@@ -1,7 +1,8 @@
 package adventofcode.common.spatial
 
 data class Grid2d<T>(val values: List<List<T>>) {
-    val points = values.flatMapIndexed { y, row -> List(row.size) { x -> Point2d(x, y) } }
+    /** Set of points contained in this grid. */
+    val points = values.flatMapIndexed { y, row -> List(row.size) { x -> Point2d(x, y) } }.toSet()
 
     /** `true` for a square grid, `false` otherwise. */
     val isSquare: Boolean = values.all { row -> row.size == values.size }
@@ -19,7 +20,19 @@ data class Grid2d<T>(val values: List<List<T>>) {
     override fun toString(): String = values.joinToString("\n") { row -> row.toString() }
 
     /** Returns the number of columns for a given row in the grid. */
-    fun colsInRow(row: Int) = values[row].size
+    fun columnsInRow(row: Int) = values[row].size
+
+    /** Returns the row of elements at the given row index. */
+    fun rowAt(index: Int): List<T> = values[index]
+
+    /** Returns the column of elements at the given column index. */
+    fun columnAt(index: Int): List<T> = values.map { row -> row[index] }
+
+    /** Syntactic sugar for nested `values` list. */
+    fun rows(): List<List<T>> = values
+
+    /** Returns all the columns of the grid. */
+    fun columns(): List<List<T>> = rotate().values.map(List<T>::reversed)
 
     /** Returns `true` if the grid contains `value`. */
     operator fun contains(value: T): Boolean = values.flatten().contains(value)
@@ -73,6 +86,7 @@ data class Grid2d<T>(val values: List<List<T>>) {
     }
 
     companion object {
+        /** Create a new `Grid2d` from a `String` where each point is a character of that string. */
         operator fun invoke(values: String) = Grid2d(values.lines().map(String::toList))
     }
 }

src/main/kotlin/adventofcode/common/spatial/Point2d.kt

@@ -6,13 +6,10 @@ data class Point2d(
     val x: Long,
     val y: Long,
 ) {
+    /** Alternative constructor to allow other Number types as coordinates, e.g. `Int`s. */
     constructor(x: Number, y: Number) : this(x.toLong(), y.toLong())
 
-    /**
-     * Pretty formatted String representation.
-     *
-     * (0, 1)
-     */
+    /** Pretty formatted String representation: (0, 1) */
     override fun toString(): String = "($x, $y)"
 
     /** Add two points together by adding their x and y coordinates. */
@@ -41,7 +38,7 @@ data class Point2d(
             .map { direction -> this + direction }
             .toSet()
 
-    /** Returns the manhattan distance between two points. */
+    /** Returns the Manhattan distance between two points. */
     infix fun distanceTo(other: Point2d): Long = (x - other.x).absoluteValue + (y - other.y).absoluteValue
 
     companion object {

src/main/kotlin/adventofcode/year2024/Day04CeresSearch.kt

@@ -18,7 +18,7 @@ class Day04CeresSearch(customInput: PuzzleInput? = null) : Puzzle(customInput) {
             val length = xmas.length
 
             return (0 until rows).flatMap { row ->
-                (0 until colsInRow(row)).flatMap { col ->
+                (0 until columnsInRow(row)).flatMap { col ->
                     val horizontal = (0 until length).map { y -> Point2d(row, col + y) }.filter { point -> point in this }
                     val vertical = (0 until length).map { x -> Point2d(row + x, col) }.filter { point -> point in this }
                     val rightDiagonal = (0 until length).map { d -> Point2d(row + d, col + d) }.filter { point -> point in this }
@@ -37,7 +37,7 @@ class Day04CeresSearch(customInput: PuzzleInput? = null) : Puzzle(customInput) {
             val length = mas.length
 
             return (0..rows - length).flatMap { row ->
-                (0..colsInRow(row) - length).map { col ->
+                (0..columnsInRow(row) - length).map { col ->
                     val topDiagonal = (0 until length).map { d -> Point2d(row + d, col + d) }
                     val bottomDiagonal = (0 until length).map { d -> Point2d(row + length - 1 - d, col + d) }
 

src/main/kotlin/adventofcode/year2024/Day25CodeChronicle.kt

@@ -0,0 +1,35 @@
+package adventofcode.year2024
+
+import adventofcode.Puzzle
+import adventofcode.PuzzleInput
+import adventofcode.common.cartesianProduct
+import adventofcode.common.spatial.Grid2d
+
+class Day25CodeChronicle(customInput: PuzzleInput? = null) : Puzzle(customInput) {
+    private val schematics by lazy { input.split("\n\n").map { Grid2d(it) } }
+    private val locks by lazy {
+        schematics
+            .filter { schematic -> schematic.rowAt(0).all { it == FILLED } && schematic.rowAt(schematic.rows - 1).all { it == EMPTY } }
+            .map { schematic -> Grid2d(schematic.values.drop(1).dropLast(1)) }
+            .toSet()
+    }
+    private val keys by lazy {
+        schematics
+            .map { schematic -> Grid2d(schematic.values.drop(1).dropLast(1)) }
+            .minus(locks)
+            .toSet()
+    }
+
+    override fun partOne() =
+        listOf(locks, keys)
+            .cartesianProduct()
+            .map { (lock, key) -> lock.toHeights().zip(key.toHeights()) { lockHeight, keyHeight -> lockHeight + keyHeight } }
+            .count { lockKeyPair -> lockKeyPair.all { height -> height <= 5 } }
+
+    companion object {
+        private const val FILLED = '#'
+        private const val EMPTY = '.'
+
+        private fun Grid2d<Char>.toHeights(): List<Int> = columns().map { column -> column.count { it == FILLED } }
+    }
+}