添加0344.反转字符串 Swift版本

problems/0344.反转字符串.md

@@ -203,7 +203,20 @@ var reverseString = function(s) {
 };
 ```
 
+Swift:
 
+```swift
+func reverseString(_ s: inout [Character]) {
+    var l = 0
+    var r = s.count - 1
+    while l < r {
+      	// 使用元祖
+        (s[l], s[r]) = (s[r], s[l])
+        l += 1
+        r -= 1
+    }
+}
+```