Add Day22

src/main/kotlin/Day22.kt

@@ -0,0 +1,54 @@
+import utils.AoCDay
+import utils.cartesianSquare
+import utils.mapToLong
+
+class Day22 : AoCDay() {
+    val numbers = input.mapToLong()
+    override fun part1(): Any {
+        return numbers.sumOf {
+            var result = it
+            repeat(2000) {
+                result = calculateNumber(result)
+            }
+            result
+        }
+    }
+
+    override fun part2(): Any {
+        val priceChanges = numbers.map {
+            val prices = mutableListOf(it % 10)
+            var result = it
+            repeat(2000) {
+                result = calculateNumber(result)
+                prices += result % 10
+            }
+
+            prices.windowed(2).map { (a, b) -> b - a to b }.windowed(4).map { l ->
+                l.map { it.first } to l.last().second
+            }.reversed().associate { it }
+        }
+        val allSequences = (-9L..9L).cartesianSquare().cartesianSquare().map { (a, b) ->
+            listOf(a.first, a.second, b.first, b.second)
+        }
+        return allSequences.maxOf { sequence -> priceChanges.sumOf { cost -> cost[sequence] ?: 0 } }
+    }
+
+    fun calculateNumber(secretNumber: Long): Long {
+        var result = secretNumber
+        result = prune(mix(result * 64, result))
+        result = prune(mix(result / 32, result))
+        return prune(mix(result * 2048, result))
+    }
+
+    fun mix(value: Long, secretNumber: Long): Long {
+        return value xor secretNumber
+    }
+
+    fun prune(secretNumber: Long): Long {
+        return secretNumber % 16777216L
+    }
+}
+
+fun main() {
+    Day22().execute()
+}

src/main/kotlin/utils/Extensions.kt

@@ -109,3 +109,4 @@ fun List<String>.chunkedInput(): List<List<String>> {
     return this.joinToString("\n").split("\n\n").map { it.split("\n") }
 }
 
+fun <T> Iterable<T>.cartesianSquare(): List<Pair<T, T>> = flatMap { v -> map { v to it } }