Add helper functions

Sources/App/Extensions/Array+Extensions.swift

@@ -0,0 +1,11 @@
+import Foundation
+
+extension Array {
+    
+    func rotated(toStartAt index: Int) -> [Element] {
+        guard index != 0 else {
+            return self
+        }
+        return Array(self[index..<count] + self[0..<index])
+    }
+}

Sources/App/Extensions/Power.swift

@@ -0,0 +1,20 @@
+import Foundation
+
+precedencegroup PowerPrecedence { higherThan: MultiplicationPrecedence }
+infix operator ^^ : PowerPrecedence
+func ^^ (radix: Int, power: Int) -> Int {
+    switch power {
+    case Int.min..<0:
+        return 0
+    case 0:
+        return 1
+    case 1:
+        return radix
+    default:
+        var result = radix
+        for _ in 1..<power {
+            result *= radix
+        }
+        return result
+    }
+}