add file ShellSortExample.swift

update code

Author: Moon1102

Shell Sort/ShellSortExample.swift

@@ -0,0 +1,33 @@
+//
+//  ShellSortExample.swift
+//  
+//
+//  Created by Cheer on 2017/2/26.
+//
+//
+
+import Foundation
+
+public func shellSort(_ list : inout [Int])
+{
+    var sublistCount = list.count / 2
+    
+    while sublistCount > 0
+    {
+        for index in 0..<arr.count{
+            
+            guard index + sublistCount < arr.count else { break }
+            
+            if arr[index] > arr[index + sublistCount]{
+                swap(&arr[index], &arr[index + sublistCount])
+            }
+            
+            guard sublistCount == 1 && index > 0 else { continue }
+            
+            if arr[index - 1] > arr[index]{
+                swap(&arr[index - 1], &arr[index])
+            }
+        }
+        sublistCount = sublistCount / 2
+    }
+}