Day 1.

src/aoc2025/Day01.kt

@@ -0,0 +1,72 @@
+package aoc2025
+
+import println
+import readInput
+
+/*
+--- Day 1: Secret Entrance ---
+https://adventofcode.com/2025/day/1
+*/
+fun main() {
+
+    val inlineTestInput = """
+L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82
+"""
+
+    fun part1(input: List<String>): Int {
+        var dialPos = 50
+        var pass = 0
+        for (i in input) {
+            dialPos = if (i.startsWith("L")) {
+                dialPos + 100 - i.substring(1).toInt()
+            } else {
+                dialPos + i.substring(1).toInt()
+            }
+            dialPos = dialPos % 100
+            if (dialPos == 0) pass++
+        }
+        return pass
+    }
+
+    fun part2(input: List<String>): Int {
+        var dialPos = 50
+        var pass = 0
+        for (i in input) {
+            val rot = i.substring(1).toInt()
+            if (rot == 0) continue
+            if (i.startsWith("L")) {
+                if (dialPos == 0) pass--
+                dialPos -= rot
+                pass += (100 - dialPos) / 100
+            } else {
+                dialPos += rot
+                pass += dialPos / 100
+            }
+            dialPos = if (dialPos < 0) (100 - (-dialPos % 100)) % 100 else dialPos % 100
+        }
+        return pass
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = inlineTestInput.trim().reader().readLines()
+    //val testInput = readInput("aoc2025/Day01_test")
+    val testInputPart1Result = part1(testInput)
+    println("Part 1 Test: $testInputPart1Result")
+    val testInputPart2Result = part2(testInput)
+    println("Part 2 Test: $testInputPart2Result")
+    check(testInputPart1Result == 3)
+    check(testInputPart2Result == 6)
+
+    val input = readInput("aoc2025/Day01")
+    part1(input).println()
+    part2(input).println()
+}