Day 6: Guard Gallivant

README.md

@@ -10,4 +10,4 @@ Development occurs in language-specific directories:
 |[Day3.hs](hs/src/Day3.hs)|[Day3.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day3.kt)|[day3.py](py/aoc2024/day3.py)|[day3.rs](rs/src/day3.rs)|
 |[Day4.hs](hs/src/Day4.hs)|[Day4.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day4.kt)|[day4.py](py/aoc2024/day4.py)|[day4.rs](rs/src/day4.rs)|
 |[Day5.hs](hs/src/Day5.hs)|[Day5.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day5.kt)|[day5.py](py/aoc2024/day5.py)|[day5.rs](rs/src/day5.rs)|
-|[Day6.hs](hs/src/Day6.hs)||||
+|[Day6.hs](hs/src/Day6.hs)|[Day6.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day6.kt)|||

kt/aoc2024-exe/build.gradle.kts

@@ -37,9 +37,15 @@ kotlin {
     applyHierarchyTemplate {
         withSourceSetTree(KotlinSourceSetTree("bench"))
         common {
-            withJvm()
-            withWasmJs()
-            withNative()
+            group("blocking") {
+                withJvm()
+                group("native") {
+                    withNative()
+                }
+            }
+            group("nonblocking") {
+                withWasmJs()
+            }
         }
     }
 

kt/aoc2024-exe/src/blockingBench/kotlin/com/github/ephemient/aoc2024/exe/Day6Bench.kt

@@ -0,0 +1,35 @@
+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.Day6
+import kotlinx.benchmark.Benchmark
+import kotlinx.benchmark.Blackhole
+import kotlinx.benchmark.Scope
+import kotlinx.benchmark.Setup
+import kotlinx.benchmark.State
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
+
+@State(Scope.Benchmark)
+class Day6Bench {
+    private lateinit var input: String
+
+    @Setup
+    fun setup() {
+        input = getDayInput(6)
+    }
+
+    @Benchmark
+    fun part1() = Day6(input).part1()
+
+    @Benchmark
+    fun part2() = runBlocking(Dispatchers.Default) {
+        Day6(input).part2()
+    }
+
+    @Benchmark
+    fun both(bh: Blackhole) = runBlocking(Dispatchers.Default) {
+        val day6 = Day6(input)
+        bh.consume(day6.part1())
+        bh.consume(day6.part2())
+    }
+}

kt/aoc2024-exe/src/nonblockingBench/kotlin/com/github/ephemient/aoc2024/exe/Day6Bench.kt

@@ -0,0 +1,20 @@
+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.Day6
+import kotlinx.benchmark.Benchmark
+import kotlinx.benchmark.Scope
+import kotlinx.benchmark.Setup
+import kotlinx.benchmark.State
+
+@State(Scope.Benchmark)
+class Day6Bench {
+    private lateinit var input: String
+
+    @Setup
+    fun setup() {
+        input = getDayInput(6)
+    }
+
+    @Benchmark
+    fun part1() = Day6(input).part1()
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day6.kt

@@ -0,0 +1,51 @@
+package com.github.ephemient.aoc2024
+
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.asFlow
+import kotlinx.coroutines.flow.count
+import kotlinx.coroutines.flow.filter
+import kotlinx.coroutines.flow.flatMapMerge
+import kotlinx.coroutines.flow.flowOf
+
+class Day6(input: String) {
+    private val lines = input.lines()
+    private val initialPosition = lines.withIndex().firstNotNullOf { (y, line) ->
+        val x = line.indexOf('^')
+        if (x >= 0) y to x else null
+    }
+
+    fun part1() = lines.walk(initialPosition).mapTo(mutableSetOf()) { it.first }.size
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    suspend fun part2() = lines.walk(initialPosition)
+        .mapTo(mutableSetOf()) { it.first }
+        .apply { remove(initialPosition) }
+        .asFlow()
+        .flatMapMerge { (y, x) ->
+            val lines = lines.toMutableList()
+            lines[y] = StringBuilder(lines[y]).apply { set(x, '#') }.toString()
+            flowOf(Unit).filter { !lines.walk(initialPosition).all(mutableSetOf<Any?>()::add) }
+        }
+        .count()
+
+    companion object {
+        private fun List<String>.walk(position: IntPair) = sequence {
+            var (y, x) = position
+            var dy = -1
+            var dx = 0
+            while (true) {
+                yield(Pair(y to x, dy to dx))
+                val nextY = y + dy
+                val nextX = x + dx
+                when (getOrNull(nextY)?.getOrNull(nextX)) {
+                    null -> break
+                    '#' -> dy = dx.also { dx = -dy }
+                    else -> {
+                        y = nextY
+                        x = nextX
+                    }
+                }
+            }
+        }
+    }
+}

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

@@ -6,6 +6,7 @@ val days: List<Day> = listOf(
     Day(3, ::Day3, Day3::part1, Day3::part2),
     Day(4, ::Day4, Day4::part1, Day4::part2),
     Day(5, ::Day5, Day5::part1, Day5::part2),
+    Day(6, ::Day6, Day6::part1, Day6::part2),
 )
 
 data class Day(

kt/aoc2024-lib/src/commonTest/kotlin/com/github/ephemient/aoc2024/Day6Test.kt

@@ -0,0 +1,33 @@
+package com.github.ephemient.aoc2024
+
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day6Test {
+    @Test
+    fun part1() {
+        assertEquals(41, Day6(example).part1())
+    }
+
+    @Test
+    fun part2() = runTest{
+        assertEquals(6, Day6(example).part2())
+    }
+
+    companion object {
+        private val example =
+            """
+            |....#.....
+            |.........#
+            |..........
+            |..#.......
+            |.......#..
+            |..........
+            |.#..^.....
+            |........#.
+            |#.........
+            |......#...
+            |""".trimMargin()
+    }
+}