Add Day11

src/main/kotlin/Day11.kt

@@ -0,0 +1,45 @@
+import utils.AoCDay
+import utils.isEven
+import utils.splitAndMapToLong
+
+class Day11 : AoCDay() {
+    val stones = input.first().splitAndMapToLong()
+
+    override fun part1(): Any {
+        return blink(25)
+    }
+
+    override fun part2(): Any {
+        return blink(75)
+    }
+
+    private fun blink(times: Int): Long {
+        var map = mutableMapOf<Long, Long>()
+        stones.forEach {
+            map[it] = (map[it] ?: 0) + 1
+        }
+        repeat(times) {
+            var newMap = mutableMapOf<Long, Long>()
+            for ((number, amount) in map) {
+                if (number == 0L) {
+                    newMap[1] = (newMap[1] ?: 0) + amount
+                } else if (number.toString().length.isEven()) {
+                    val string = number.toString()
+                    val half = string.length / 2
+                    val firstHalf = string.substring(0, half).toLong()
+                    val secondHalf = string.substring(half).toLong()
+                    newMap[firstHalf] = (newMap[firstHalf] ?: 0) + amount
+                    newMap[secondHalf] = (newMap[secondHalf] ?: 0) + amount
+                } else {
+                    newMap[number * 2024] = (newMap[number * 2024] ?: 0) + amount
+                }
+            }
+            map = newMap
+        }
+        return map.values.sum()
+    }
+}
+
+fun main() {
+    Day11().execute()
+}