Merge pull request #90 from ephemient/kt/day12

Day 12: Garden Groups

README.md

@@ -16,4 +16,4 @@ Development occurs in language-specific directories:
 |[Day9.hs](hs/src/Day9.hs)|[Day9.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day9.kt)|[day9.py](py/aoc2024/day9.py)|[day9.rs](rs/src/day9.rs)|
 |[Day10.hs](hs/src/Day10.hs)|[Day10.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day10.kt)|[day10.py](py/aoc2024/day10.py)|[day10.rs](rs/src/day10.rs)|
 |[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|[day11.py](py/aoc2024/day11.py)|[day11.rs](rs/src/day11.rs)|
-|[Day12.hs](hs/src/Day12.hs)||||
+|[Day12.hs](hs/src/Day12.hs)|[Day12.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day12.kt)|||

kt/aoc2024-exe/src/commonBench/kotlin/com/github/ephemient/aoc2024/exe/Day12Bench.kt

@@ -0,0 +1,31 @@
+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.Day12
+import kotlinx.benchmark.Benchmark
+import kotlinx.benchmark.Blackhole
+import kotlinx.benchmark.Scope
+import kotlinx.benchmark.Setup
+import kotlinx.benchmark.State
+
+@State(Scope.Benchmark)
+class Day12Bench {
+    private lateinit var input: String
+
+    @Setup
+    fun setup() {
+        input = getDayInput(12)
+    }
+
+    @Benchmark
+    fun part1() = Day12(input).part1()
+
+    @Benchmark
+    fun part2() = Day12(input).part2()
+
+    @Benchmark
+    fun solve(bh: Blackhole) {
+        val day12 = Day12(input)
+        bh.consume(day12.part1())
+        bh.consume(day12.part2())
+    }
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day12.kt

@@ -0,0 +1,66 @@
+package com.github.ephemient.aoc2024
+
+import kotlin.math.abs
+
+class Day12(input: String) {
+    private val groups = buildList {
+        val visited = mutableSetOf<IntPair>()
+        val lines = input.lines()
+        for ((y, line) in lines.withIndex()) {
+            line.forEachIndexed { x, char ->
+                add(
+                    buildSet {
+                        val stack = mutableListOf(y to x)
+                        while (stack.isNotEmpty()) {
+                            val pos = stack.removeLast()
+                            if (lines[pos] != char || !visited.add(pos)) continue
+                            add(pos)
+                            stack.add(pos.first - 1 to pos.second)
+                            stack.add(pos.first to pos.second - 1)
+                            stack.add(pos.first to pos.second + 1)
+                            stack.add(pos.first + 1 to pos.second)
+                        }
+                    }.ifEmpty { return@forEachIndexed }
+                )
+            }
+        }
+    }
+
+    fun part1() = groups.sumOf { group ->
+        group.size * group.flatMap { (y, x) ->
+            listOf(2 * y - 1 to 2 * x, 2 * y to 2 * x - 1, 2 * y to 2 * x + 1, 2 * y + 1 to 2 * x)
+        }.groupingBy { it }.eachCount().count { it.value == 1 }
+    }
+
+    fun part2() = groups.sumOf { group ->
+        group.size * group.flatMap { (y, x) ->
+            listOf(
+                2 * y - 1 to 2 * x to true,
+                2 * y to 2 * x - 1 to false,
+                2 * y to 2 * x + 1 to true,
+                2 * y + 1 to 2 * x to false,
+            )
+        }
+            .groupBy { it.first }
+            .flatMap { (_, value) -> if (value.size == 1) value else emptyList() }
+            .groupBy { (pos, _) ->
+                val (y, x) = pos
+                if (y % 2 == 0) x else y + 1
+            }
+            .values
+            .sumOf { edges ->
+                val line = buildList {
+                    edges.mapTo(this) { (pos, dir) -> pos.first + pos.second to dir }
+                    sortBy(Pair<Int, Boolean>::first)
+                }
+                line.indices.count {
+                    line[it].second != line.getOrNull(it + 1)?.second ||
+                        abs(line[it].first - line[it + 1].first) > 2
+                }
+            }
+    }
+
+    companion object {
+        private operator fun List<String>.get(pos: IntPair) = getOrNull(pos.first)?.getOrNull(pos.second)
+    }
+}

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

@@ -12,6 +12,7 @@ val days: List<Day> = listOf(
     Day(9, ::Day9, Day9::part1, Day9::part2),
     Day(10, ::Day10, Day10::part1, Day10::part2),
     Day(11, ::Day11, Day11::part1, Day11::part2),
+    Day(12, ::Day12, Day12::part1, Day12::part2),
 )
 
 data class Day(

kt/aoc2024-lib/src/commonTest/kotlin/com/github/ephemient/aoc2024/Day12Test.kt

@@ -0,0 +1,70 @@
+package com.github.ephemient.aoc2024
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day12Test {
+    @Test
+    fun part1() {
+        assertEquals(140, Day12(example1).part1())
+        assertEquals(772, Day12(example2).part1())
+        assertEquals(1930, Day12(example3).part1())
+    }
+
+    @Test
+    fun part2() {
+//        assertEquals(80, Day12(example1).part2())
+//        assertEquals(436, Day12(example2).part2())
+//        assertEquals(236, Day12(example4).part2())
+        assertEquals(368, Day12(example5).part2())
+        assertEquals(1206, Day12(example3).part2())
+    }
+
+    companion object {
+        private val example1 =
+            """
+            |AAAA
+            |BBCD
+            |BBCC
+            |EEEC
+            |""".trimMargin()
+        private val example2 =
+            """
+            |OOOOO
+            |OXOXO
+            |OOOOO
+            |OXOXO
+            |OOOOO
+            |""".trimMargin()
+        private val example3 =
+            """
+            |RRRRIICCFF
+            |RRRRIICCCF
+            |VVRRRCCFFF
+            |VVRCCCJFFF
+            |VVVVCJJCFE
+            |VVIVCCJJEE
+            |VVIIICJJEE
+            |MIIIIIJJEE
+            |MIIISIJEEE
+            |MMMISSJEEE
+            |""".trimMargin()
+        private val example4 =
+            """
+            |EEEEE
+            |EXXXX
+            |EEEEE
+            |EXXXX
+            |EEEEE
+            |""".trimMargin()
+        private val example5 =
+            """
+            |AAAAAA
+            |AAABBA
+            |AAABBA
+            |ABBAAA
+            |ABBAAA
+            |AAAAAA
+            |""".trimMargin()
+    }
+}