feat: add swift implementation to lcci problem: No.16.07 (doocs#2730)

Author: klever34

lcci/16.07.Maximum/README.md

@@ -64,6 +64,16 @@ function maximum(a: number, b: number): number {
 }
 ```
 
+```swift
+class Solution {
+    func maximum(_ a: Int, _ b: Int) -> Int {
+        let diff = Int64(a) - Int64(b)
+        let k = Int((diff >> 63) & 1)
+        return a * (k ^ 1) + b * k
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/16.07.Maximum/README_EN.md

@@ -66,6 +66,16 @@ function maximum(a: number, b: number): number {
 }
 ```
 
+```swift
+class Solution {
+    func maximum(_ a: Int, _ b: Int) -> Int {
+        let diff = Int64(a) - Int64(b)
+        let k = Int((diff >> 63) & 1)
+        return a * (k ^ 1) + b * k
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/16.07.Maximum/Solution.swift

@@ -0,0 +1,7 @@
+class Solution {
+    func maximum(_ a: Int, _ b: Int) -> Int {
+        let diff = Int64(a) - Int64(b)
+        let k = Int((diff >> 63) & 1)
+        return a * (k ^ 1) + b * k
+    }
+}