Data commit

Task/Perfect-shuffle/Swift/perfect-shuffle.swift

@@ -0,0 +1,37 @@
+func perfectShuffle<T>(_ arr: [T]) -> [T]? {
+  guard arr.count & 1 == 0 else {
+    return nil
+  }
+
+  let half = arr.count / 2
+  var res = [T]()
+
+  for i in 0..<half {
+    res.append(arr[i])
+    res.append(arr[i + half])
+  }
+
+  return res
+}
+
+let decks = [
+  Array(1...8),
+  Array(1...24),
+  Array(1...52),
+  Array(1...100),
+  Array(1...1020),
+  Array(1...1024),
+  Array(1...10000)
+]
+
+for deck in decks {
+  var shuffled = deck
+  var shuffles = 0
+
+  repeat {
+    shuffled = perfectShuffle(shuffled)!
+    shuffles += 1
+  } while shuffled != deck
+
+  print("Deck of \(shuffled.count) took \(shuffles) shuffles to get back to original order")
+}