Merge pull request kodecocodes#549 from remlostime/count-sort-swift

[Swift 4] Update Counting Sort

Author: kelvinlauKL

Counting Sort/CountingSort.playground/Contents.swift

@@ -1,5 +1,10 @@
 //: Playground - noun: a place where people can play
 
+// last checked with Xcode 9.0b4
+#if swift(>=4.0)
+print("Hello, Swift 4!")
+#endif
+
 enum CountingSortError: Error {
   case arrayEmpty
 }