Refactor Day 1 - reusable function for part 1/2

GitOrigin-RevId: 0995aa825e3a0399b9d23bf4131303f7c2669368

Author: Will Molloy

advent-of-code/src/main/kotlin/com/willmolloy/adventofcode/_2025/Day1.kt

@@ -6,50 +6,17 @@ import com.willmolloy.adventofcode.common.Input
 /** https://adventofcode.com/2025/day/1 */
 object Day1 : Day(2025, 1) {
 
-  override fun part1(input: Input): Any {
-    val lines = input.lines()
-
-    var res = 0
-    var dial = 50
-
-    for (line in lines) {
-      var nums = line.substring(1).toInt()
-
-      when (line[0]) {
-        'L' -> {
-          // dec
-          while (nums-- > 0) {
-            dial--
-            // TODO there must be a better way - modulo? But then part2 is broken...?
-            if (dial == -1) {
-              dial = 99
-            }
-          }
-        }
-        'R' -> {
-          // inc
-          while (nums-- > 0) {
-            dial++
-            if (dial == 100) {
-              dial = 0
-            }
-          }
-        }
-      }
-
-      if (dial == 0) {
-        res++
-      }
-    }
+  override fun part1(input: Input) = solve(input).first
 
-    return res
-  }
+  override fun part2(input: Input) = solve(input).second
 
-  // just move the res count into the inner loops...
-  override fun part2(input: Input): Any {
+  private fun solve(input: Input): Pair<Int, Int> {
     val lines = input.lines()
 
-    var res = 0
+    var part1Res = 0
+    // just move the res count into the inner loops...
+    var part2Res = 0
+
     var dial = 50
 
     for (line in lines) {
@@ -60,11 +27,13 @@ object Day1 : Day(2025, 1) {
           // dec
           while (nums-- > 0) {
             dial--
+            // TODO there must be a better way - modulo? But then part2 is broken...?
             if (dial == -1) {
               dial = 99
             }
+
             if (dial == 0) {
-              res++
+              part2Res++
             }
           }
         }
@@ -75,14 +44,19 @@ object Day1 : Day(2025, 1) {
             if (dial == 100) {
               dial = 0
             }
+
             if (dial == 0) {
-              res++
+              part2Res++
             }
           }
         }
       }
+
+      if (dial == 0) {
+        part1Res++
+      }
     }
 
-    return res
+    return Pair(part1Res, part2Res)
   }
 }

advent-of-code/src/main/kotlin/com/willmolloy/adventofcode/_2025/Day2.kt

@@ -6,18 +6,16 @@ import com.willmolloy.adventofcode.common.Input
 /** https://adventofcode.com/2025/day/2 */
 object Day2 : Day(2025, 2) {
 
-  override fun part1(input: Input): Any {
-    return solve(input) { it.take(it.length / 2) == it.drop(it.length / 2) }
-  }
+  override fun part1(input: Input) =
+    solve(input) { id -> id.take(id.length / 2) == id.drop(id.length / 2) }
 
-  override fun part2(input: Input): Any {
-    return solve(input) {
-      ((1..it.length / 2).any { chunkSize ->
-        val chunked = it.chunked(chunkSize)
+  override fun part2(input: Input) =
+    solve(input) { id ->
+      ((1..id.length / 2).any { chunkSize ->
+        val chunked = id.chunked(chunkSize)
         chunked.all { s -> s == chunked.first() }
       })
     }
-  }
 
   private fun solve(input: Input, test: (String) -> Boolean): Long {
     val ranges = input.string().split(",")