Day01 - Part 1

Author: ath0s

src/main/kotlin/Day01.kt

@@ -0,0 +1,79 @@
+import Day01.Rotation.Left
+import Day01.Rotation.Right
+import kotlin.io.path.readLines
+
+class Day01 : Day {
+    private val start = 50
+
+    override fun partOne(filename: String, verbose: Boolean): Int {
+        val rotations = filename.asPath().readLines().map { line ->
+            when (line.first()) {
+                'L' -> Left(line.drop(1).toInt())
+                'R' -> Right(line.drop(1).toInt())
+                else -> throw IllegalArgumentException("Unexpected line $line")
+            }
+        }
+
+        if (verbose) {
+            rotations.forEach {
+                println(it)
+            }
+        }
+
+        var current = start
+
+        if (verbose) {
+            println("The dial starts by pointing at $current")
+        }
+
+        var zeroCount = 0
+        rotations.forEach { rotation ->
+            current = rotation.rotate(current)
+            if (verbose) {
+                println("The dial is rotated $rotation to point at $current")
+            }
+            if (current == 0) {
+                zeroCount++
+            }
+        }
+
+        return zeroCount
+    }
+
+    override fun partTwo(filename: String, verbose: Boolean): Any {
+        TODO("Not yet implemented")
+    }
+
+    private sealed interface Rotation {
+        fun rotate(current: Int): Int
+
+        data class Left(private val steps: Int) : Rotation {
+            override fun rotate(current: Int): Int {
+                var next = current - steps
+                while (next < 0) {
+                    next += 100
+                }
+                return next
+            }
+
+            override fun toString() = "L$steps"
+        }
+
+        data class Right(private val steps: Int) : Rotation {
+            override fun rotate(current: Int): Int {
+                var next = current + steps
+                while (next > 99) {
+                    next -= 100
+                }
+                return next
+            }
+
+            override fun toString() = "R$steps"
+        }
+    }
+
+    companion object : Day.Main("Day01.txt") {
+        @JvmStatic
+        fun main(args: Array<String>) = main()
+    }
+}