Day 3: Mull It Over

README.md

@@ -7,4 +7,4 @@ Development occurs in language-specific directories:
 |--:|--:|--:|--:|
 |[Day1.hs](hs/src/Day1.hs)|[Day1.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day1.kt)|[day1.py](py/aoc2024/day1.py)|[day1.rs](rs/src/day1.rs)|
 |[Day2.hs](hs/src/Day2.hs)|[Day2.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day2.kt)|[day2.py](py/aoc2024/day2.py)|[day2.rs](rs/src/day2.rs)|
-|[Day3.hs](hs/src/Day3.hs)||||
+|[Day3.hs](hs/src/Day3.hs)|[Day3.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day3.kt)|||

kt/aoc2024-exe/src/commonBench/kotlin/com/github/ephemient/aoc2024/exe/Day3Bench.kt

@@ -0,0 +1,23 @@
+package com.github.ephemient.aoc2024.exe
+
+import com.github.ephemient.aoc2024.Day3
+import kotlinx.benchmark.Benchmark
+import kotlinx.benchmark.Scope
+import kotlinx.benchmark.Setup
+import kotlinx.benchmark.State
+
+@State(Scope.Benchmark)
+class Day3Bench {
+    private lateinit var input: String
+
+    @Setup
+    fun setup() {
+        input = getDayInput(3)
+    }
+
+    @Benchmark
+    fun part1() = Day3(input).part1()
+
+    @Benchmark
+    fun part2() = Day3(input).part2()
+}

kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day3.kt

@@ -0,0 +1,31 @@
+package com.github.ephemient.aoc2024
+
+class Day3(private val input: String) {
+    fun part1(): Int = regex1.findAll(input).sumOf { match ->
+        val (x, y) = match.destructured
+        x.toInt() * y.toInt()
+    }
+
+    fun part2(): Int {
+        var enable = true
+        return regex2.findAll(input)
+            .filter { match ->
+                val (yes, no) = match.destructured
+                enable = when {
+                    yes.isNotEmpty() -> true
+                    no.isNotEmpty() -> false
+                    else -> return@filter enable
+                }
+                false
+            }
+            .sumOf { match ->
+                val (_, _, x, y) = match.destructured
+                x.toInt() * y.toInt()
+            }
+    }
+
+    companion object {
+        private val regex1 = """mul\((\d+),(\d+)\)""".toRegex()
+        private val regex2 = """(do\(\))|(don't\(\))|mul\((\d+),(\d+)\)""".toRegex()
+    }
+}

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

@@ -3,6 +3,7 @@ package com.github.ephemient.aoc2024
 val days: List<Day> = listOf(
     Day(1, ::Day1, Day1::part1, Day1::part2),
     Day(2, ::Day2, Day2::part1, Day2::part2),
+    Day(3, ::Day3, Day3::part1, Day3::part2),
 )
 
 data class Day(

kt/aoc2024-lib/src/commonTest/kotlin/com/github/ephemient/aoc2024/Day3Test.kt

@@ -0,0 +1,27 @@
+package com.github.ephemient.aoc2024
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day3Test {
+    @Test
+    fun part1() {
+        assertEquals(161, Day3(example1).part1())
+    }
+
+    @Test
+    fun part2() {
+        assertEquals(48, Day3(example2).part2())
+    }
+
+    companion object {
+        private val example1 =
+            """
+            |xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))
+            |""".trimMargin()
+        private val example2 =
+            """
+            |xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
+            |""".trimMargin()
+    }
+}