implement gaurded array first

Author: TheIronBorn

Select Minimum Maximum/Maximum.swift

@@ -2,12 +2,9 @@
  Finds the maximum value in an array in O(n) time.
  */
 
-func maximum<T: Comparable>(_ array: [T]) -> T? {
-    guard !array.isEmpty else {
-        return nil
-    }
-
-    var maximum = array.first!
+func maximum1<T: Comparable>(_ array: [T]) -> T? {
+    guard var maximum = array.first else { return nil }
+    
     for element in array.dropFirst() {
         maximum = element > maximum ? element : maximum
     }