Day 1: Historian Hysteria

.gitattributes

@@ -0,0 +1,3 @@
+# generated by Gradle Wrapper
+kt/gradlew linguist-generated
+kt/gradlew.bat linguist-generated

.github/workflows/kt.yml

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+name: Kotlin CI
+
+on:
+  push:
+    branches: [ main ]
+    paths: [ kt/** ]
+  pull_request:
+    branches: [ main ]
+    paths: [ kt/** ]
+
+  workflow_dispatch:
+
+jobs:
+  get-inputs:
+    uses: ephemient/aoc2024/.github/workflows/get-inputs.yml@main
+    secrets:
+      SESSION: ${{ secrets.SESSION }}
+
+  build:
+    needs: [ get-inputs ]
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/download-artifact@v4
+        with:
+          name: inputs
+          path: inputs
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+      - uses: gradle/actions/setup-gradle@v4
+      - run: ./gradlew check
+        working-directory: kt
+      - run: ./gradlew :aoc2024-exe:runJvm
+        working-directory: kt
+        env:
+          AOC2024_DATADIR: ${{ github.workspace }}/inputs

README.md

@@ -3,6 +3,6 @@
 
 Development occurs in language-specific directories:
 
-|[Haskell](hs) ![Haskell CI](https://github.com/ephemient/aoc2024/workflows/Haskell%20CI/badge.svg)|
-|--:|
-|[Day1.hs](hs/src/Day1.hs)|
+|[Haskell](hs) ![Haskell CI](https://github.com/ephemient/aoc2024/workflows/Haskell%20CI/badge.svg)|[Kotlin](kt) ![Kotlin CI](https://github.com/ephemient/aoc2024/workflows/Kotlin%20CI/badge.svg)|
+|--:|--:|
+|[Day1.hs](hs/src/Day1.hs)|[Day1.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day1.kt)|

kt/.envrc

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+export AOC2024_DATADIR=$(realpath ..)

kt/.gitignore

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+.gradle/
+.kotlin/
+.idea/
+build/
+local.properties
+*~

kt/README.md

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+# [Advent of Code 2024](https://adventofcode.com/2024)
+### my answers in [Kotlin](https://www.kotlinlang.org/) ![Kotlin CI](https://github.com/ephemient/aoc2024/workflows/Kotlin%20CI/badge.svg)
+
+This project builds with [Gradle](https://gradle.org/).
+
+Run the test suite:
+
+```sh
+./gradlew :aoc2024-lib:allTests
+```
+
+Print solutions for the inputs provided in local data files:
+
+```sh
+./gradlew :aoc2024-exe:jvmRun
+```
+
+Run all checks, including [Detekt](https://detekt.github.io/) static code analysis:
+
+```sh
+./gradlew check
+```

kt/aoc2024-exe/build.gradle.kts

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+import io.gitlab.arturbosch.detekt.Detekt
+
+plugins {
+    alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.detekt)
+}
+
+kotlin {
+    jvm {
+        mainRun {
+            mainClass = "com.github.ephemient.aoc2024.exe.Main"
+        }
+    }
+
+    sourceSets {
+        commonMain {
+            dependencies {
+                implementation(projects.aoc2024Lib)
+                implementation(libs.kotlinx.coroutines)
+            }
+        }
+    }
+}
+
+dependencies {
+    detektPlugins(libs.bundles.detekt.plugins)
+}

kt/aoc2024-exe/src/commonMain/kotlin/com/github/ephemient/aoc2024/exe/CommonMain.kt

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+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.days
+
+internal suspend fun mainImpl(args: Array<out String>) {
+    for (day in days) {
+        if ((args.isNotEmpty() || day.skipByDefault) && day.name !in args) continue
+        println("Day ${day.name}")
+        for (part in day.solver(getDayInput(day.day))) println(part())
+        println()
+    }
+}

kt/aoc2024-exe/src/commonMain/kotlin/com/github/ephemient/aoc2024/exe/IO.kt

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+package com.github.ephemient.aoc2024.exe
+
+internal expect fun getDayInput(day: Int): String

kt/aoc2024-exe/src/jvmMain/kotlin/com/github/ephemient/aoc2024/exe/IO.kt

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+package com.github.ephemient.aoc2024.exe
+
+import java.io.File
+
+internal actual fun getDayInput(day: Int): String =
+    File(System.getenv("AOC2024_DATADIR")?.ifEmpty { null } ?: ".", "day$day.txt").readText()

kt/aoc2024-exe/src/jvmMain/kotlin/com/github/ephemient/aoc2024/exe/JvmMain.kt

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+@file:JvmName("Main")
+
+package com.github.ephemient.aoc2024.exe
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+
+@Suppress("InjectDispatcher")
+suspend fun main(vararg args: String): Unit = withContext(Dispatchers.Default) {
+    mainImpl(args)
+}

kt/aoc2024-lib/build.gradle.kts

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+plugins {
+    alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.detekt)
+}
+
+kotlin {
+    jvm()
+
+    sourceSets {
+        commonMain {
+            dependencies {
+                implementation(libs.kotlinx.coroutines)
+            }
+        }
+
+        commonTest {
+            dependencies {
+                implementation(kotlin("test"))
+                implementation(libs.kotlinx.coroutines.test)
+            }
+        }
+
+        jvmTest {
+            dependencies {
+                implementation(kotlin("test-junit5"))
+                implementation(libs.junit.jupiter.api)
+                runtimeOnly(libs.junit.jupiter.engine)
+            }
+        }
+    }
+}
+
+dependencies {
+    detektPlugins(libs.bundles.detekt.plugins)
+}
+
+tasks.withType<Test>().configureEach {
+    useJUnitPlatform()
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/CommonPriorityQueue.kt

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+package com.github.ephemient.aoc2024
+
+internal class CommonPriorityQueue<E : Any>(private val comparator: Comparator<in E>) : PriorityQueue<E> {
+    private val storage = mutableListOf<E>()
+
+    override fun isEmpty(): Boolean = storage.isEmpty()
+
+    override fun add(element: E): Boolean {
+        storage.add(element)
+        var i = storage.lastIndex
+        while (i > 0) {
+            val j = (i - 1) / 2
+            val a = storage[j]
+            val b = storage[i]
+            if (comparator.compare(a, b) <= 0) break
+            storage[i] = a
+            storage[j] = b
+            i = j
+        }
+        return true
+    }
+
+    @Suppress("NestedBlockDepth")
+    @Throws(NoSuchElementException::class)
+    override fun remove(): E {
+        val first = storage.first()
+        val last = storage.removeLast()
+        if (storage.isNotEmpty()) {
+            storage[0] = last
+            var i = 0
+            while (2 * i + 2 < storage.size) {
+                val j = if (comparator.compare(storage[2 * i + 1], storage[2 * i + 2]) < 0) 2 * i + 1 else 2 * i + 2
+                if (comparator.compare(storage[i], storage[j]) <= 0) break
+                storage[i] = storage[j].also { storage[j] = storage[i] }
+                i = j
+            }
+            if (2 * i + 1 == storage.lastIndex && comparator.compare(storage[i], storage.last()) > 0) {
+                storage[i] = storage.last().also { storage[storage.lastIndex] = storage[i] }
+            }
+        }
+        return first
+    }
+
+    override fun iterator(): Iterator<E> = storage.iterator()
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day1.kt

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+package com.github.ephemient.aoc2024
+
+import kotlin.math.abs
+
+class Day1(input: String) {
+    private val left: List<Int>
+    private val right: List<Int>
+
+    init {
+        val left = mutableListOf<Int>()
+        val right = mutableListOf<Int>()
+        for (line in input.lineSequence()) {
+            val parts = line.trim().split(splitter, limit = 2)
+            val x = parts.getOrNull(0)?.toIntOrNull() ?: continue
+            val y = parts.getOrNull(1)?.toIntOrNull() ?: continue
+            left.add(x)
+            right.add(y)
+        }
+        this.left = left.toList()
+        this.right = right.toList()
+    }
+
+    fun part1() = left.sorted().zip(right.sorted(), Int::minus).sumOf(::abs)
+
+    fun part2(): Int {
+        val right = right.groupingBy { it }.eachCount()
+        return left.sumOf { it * right.getOrElse(it) { 0 } }
+    }
+
+    companion object {
+        private val splitter = """\s+""".toRegex()
+    }
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Days.kt

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+package com.github.ephemient.aoc2024
+
+val days: List<Day> = listOf(
+    Day(1, ::Day1, Day1::part1, Day1::part2),
+)
+
+data class Day(
+    val day: Int,
+    val parts: Int,
+    val solver: (String) -> List<suspend () -> Any?>,
+    val name: String = day.toString(),
+    val skipByDefault: Boolean = false,
+)
+
+fun <T> Day(
+    day: Int,
+    create: (String) -> T,
+    vararg parts: suspend (T) -> Any?,
+    name: String = day.toString(),
+    skipByDefault: Boolean = false,
+): Day = Day(
+    day = day,
+    parts = parts.size,
+    solver = { with(create(it)) { parts.map { suspend { it.invoke(this) } } } },
+    name = name,
+    skipByDefault = skipByDefault,
+)

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/IntPair.kt

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+package com.github.ephemient.aoc2024
+
+data class IntPair(val first: Int, val second: Int) {
+    override fun toString(): String = "($first, $second)"
+}
+
+infix fun Int.to(other: Int): IntPair = IntPair(this, other)

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Math.kt

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+package com.github.ephemient.aoc2024
+
+fun gcd(x: Long, y: Long): Long {
+    var a = x
+    var b = y
+    while (b != 0L) a = b.also { b = a.mod(b) }
+    return a
+}
+
+fun lcm(x: Long, y: Long): Long = x / gcd(x, y) * y

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Parallel.kt

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+package com.github.ephemient.aoc2024
+
+import kotlinx.coroutines.flow.channelFlow
+import kotlinx.coroutines.flow.fold
+import kotlinx.coroutines.launch
+
+suspend fun <T> Iterable<T>.parSum(block: (T) -> Long): Long = channelFlow {
+    for (value in this@parSum) {
+        launch {
+            send(block(value))
+        }
+    }
+}.fold(0, Long::plus)

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/PriorityQueue.kt

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+package com.github.ephemient.aoc2024
+
+interface PriorityQueue<E : Any> : Iterable<E> {
+    fun isEmpty(): Boolean
+
+    fun add(element: E): Boolean
+
+    @Throws(NoSuchElementException::class)
+    fun remove(): E
+}
+
+expect fun <E : Any> PriorityQueue(comparator: Comparator<E>): PriorityQueue<E>

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Transpose.kt

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+package com.github.ephemient.aoc2024
+
+fun Iterable<String>.transpose(): List<String> = buildList {
+    val strings = this@transpose.filterTo(mutableListOf()) { it.isNotEmpty() }
+    var i = 0
+    while (strings.isNotEmpty()) {
+        add(buildString(strings.size) { for (string in strings) append(string[i]) })
+        i++
+        strings.removeAll { it.length == i }
+    }
+}

kt/aoc2024-lib/src/commonTest/kotlin/com/github/ephemient/aoc2024/Day1Test.kt

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+package com.github.ephemient.aoc2024
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day1Test {
+    @Test
+    fun part1() {
+        assertEquals(11, Day1(example).part1())
+    }
+
+    @Test
+    fun part2() {
+        assertEquals(31, Day1(example).part2())
+    }
+
+    companion object {
+        private val example =
+            """
+            |3   4
+            |4   3
+            |2   5
+            |1   3
+            |3   9
+            |3   3
+            |""".trimMargin()
+    }
+}

kt/aoc2024-lib/src/jvmMain/kotlin/com/github/ephemient/aoc2024/JvmPriorityQueue.kt

@@ -0,0 +1,8 @@
+package com.github.ephemient.aoc2024
+
+internal class JvmPriorityQueue<E : Any>(comparator: Comparator<E>) :
+    PriorityQueue<E>,
+    java.util.PriorityQueue<E>(comparator)
+
+actual fun <E : Any> PriorityQueue(comparator: Comparator<E>): PriorityQueue<E> =
+    JvmPriorityQueue(comparator)

kt/build.gradle.kts

@@ -0,0 +1,5 @@
+plugins {
+    alias(libs.plugins.kotlin.multiplatform) apply false
+}
+
+group = "com.github.ephemient.aoc2024"