Day 25: Full of Hot Air

README.md

@@ -30,4 +30,4 @@ Development occurs in language-specific directories:
 |[Day22.hs](hs/src/Day22.hs)|[Day22.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day22.kt)|[day22.py](py/aoc2022/day22.py)|[day22.rs](rs/src/day22.rs)|
 |[Day23.hs](hs/src/Day23.hs)|[Day23.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day23.kt)|[day23.py](py/aoc2022/day23.py)|[day23.rs](rs/src/day23.rs)|
 |[Day24.hs](hs/src/Day24.hs)|[Day24.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day24.kt)|[day24.py](py/aoc2022/day24.py)|[day24.rs](rs/src/day24.rs)|
-|[Day25.hs](hs/src/Day25.hs)|
+|[Day25.hs](hs/src/Day25.hs)|[Day25.kt](kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day25.kt)|

kt/src/commonMain/kotlin/com/github/ephemient/aoc2022/Day25.kt

@@ -0,0 +1,25 @@
+package com.github.ephemient.aoc2022
+
+@Day
+class Day25(private val lines: List<String>) {
+    @Day.Part
+    fun part1(): String = buildString {
+        var n = lines.sumOf { line ->
+            line.fold(0L) { k, c ->
+                5 * k + when (c) {
+                    '=' -> -2
+                    '-' -> -1
+                    else -> c.digitToInt()
+                }
+            }
+        }
+        while (n != 0L) {
+            n = n.floorDiv(5) + when (val d = n.mod(5)) {
+                3 -> 1.also { append('=') }
+                4 -> 1.also { append('-') }
+                else -> 0.also { append(d.digitToChar()) }
+            }
+        }
+        reverse()
+    }
+}

kt/src/commonTest/kotlin/com/github/ephemient/aoc2022/Day25Test.kt

@@ -0,0 +1,11 @@
+package com.github.ephemient.aoc2022
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class Day25Test {
+    @Test
+    fun part1() {
+        assertEquals("2=-1=0", Day25(getTestInput(25)).part1())
+    }
+}

kt/src/jvmTest/resources/day25.txt

@@ -0,0 +1,13 @@
+1=-0-2
+12111
+2=0=
+21
+2=01
+111
+20012
+112
+1=-1=
+1-12
+12
+1=
+122