diff --git a/problems/0344.反转字符串.md b/problems/0344.反转字符串.md
index a5f18d58..a02c27d5 100644
--- a/problems/0344.反转字符串.md
+++ b/problems/0344.反转字符串.md
@@ -206,6 +206,7 @@ var reverseString = function(s) {
 Swift:
 
 ```swift
+// 双指针 - 元组
 func reverseString(_ s: inout [Character]) {
     var l = 0
     var r = s.count - 1
@@ -216,11 +217,18 @@ func reverseString(_ s: inout [Character]) {
         r -= 1
     }
 }
+
+// 双指针法 - 库函数
+func reverseString(_ s: inout [Character]) {
+    var j = s.count - 1
+    for i in 0 ..< Int(Double(s.count) * 0.5) {
+        s.swapAt(i, j)
+        j -= 1
+    }
+}
 ```
 
 
-
-
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 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)