Extract Long.digitCount() - a function that counts digits of a Long number

Author: rhaendel

src/main/kotlin/de/ronny_h/aoc/extensions/Digits.kt

@@ -0,0 +1,16 @@
+package de.ronny_h.aoc.extensions
+
+/**
+ * Counts the number of digits of the given Long number.
+ */
+fun Long.digitCount(): Int {
+    if (this == 0L) return 1
+
+    var count = 0
+    var currentNumber = this
+    while (currentNumber > 0) {
+        currentNumber /= 10
+        count++
+    }
+    return count
+}

src/main/kotlin/de/ronny_h/aoc/year24/day11/PlutonianPebbles.kt

@@ -1,6 +1,7 @@
 package de.ronny_h.aoc.year24.day11
 
 import de.ronny_h.aoc.AdventOfCode
+import de.ronny_h.aoc.extensions.digitCount
 import de.ronny_h.aoc.extensions.memoize
 
 fun main() = PlutonianPebbles().run(193899, 229682160383225)
@@ -12,18 +13,6 @@ class PlutonianPebbles : AdventOfCode<Long>(2024, 11) {
         .map(String::toLong)
         .toMutableList()
 
-    private fun Long.digitCount(): Int {
-        if (this == 0L) return 1
-
-        var count = 0
-        var currentNumber = this
-        while (currentNumber > 0) {
-            currentNumber /= 10
-            count++
-        }
-        return count
-    }
-
     private fun tenToPowerOf(digitCount: Int): Int {
         var tens = 10
         repeat((digitCount / 2) - 1) {

src/test/kotlin/de/ronny_h/aoc/extensions/DigitsTest.kt

@@ -0,0 +1,16 @@
+package de.ronny_h.aoc.extensions
+
+import io.kotest.core.spec.style.StringSpec
+import io.kotest.data.forAll
+import io.kotest.data.row
+import io.kotest.matchers.shouldBe
+
+class DigitsTest : StringSpec({
+    "Digits are counted" {
+        forAll(
+            row(0L, 1), row(123L, 3), row(1234567890, 10)
+        ) { number, digits ->
+            number.digitCount() shouldBe digits
+        }
+    }
+})