feat: add swift implementation to lcof problem: No.40 (doocs#2921)

Author: klever34

lcof/面试题40. 最小的k个数/README.md

@@ -208,6 +208,17 @@ public class Solution {
 }
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    func getLeastNumbers(_ arr: [Int], _ k: Int) -> [Int] {
+        let sortedArr = arr.sorted()
+        return Array(sortedArr.prefix(k))
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题40. 最小的k个数/Solution.swift

@@ -0,0 +1,6 @@
+class Solution {
+    func getLeastNumbers(_ arr: [Int], _ k: Int) -> [Int] {
+        let sortedArr = arr.sorted()
+        return Array(sortedArr.prefix(k))
+    }
+}