From 9977fb5996d2e593d0bc220754d91c0abeec181f Mon Sep 17 00:00:00 2001
From: Jijie LIU <liujijieseason@gmail.com>
Date: Wed, 19 Oct 2022 21:47:25 +0200
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---
 problems/0541.反转字符串II.md | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/problems/0541.反转字符串II.md b/problems/0541.反转字符串II.md
index 3dd6b1e8..02ad92a0 100644
--- a/problems/0541.反转字符串II.md
+++ b/problems/0541.反转字符串II.md
@@ -412,6 +412,26 @@ object Solution {
 }
 ```
 
+版本三: (递归)
+```scala
+import scala.annotation.tailrec
+
+object Solution {
+  def reverseStr(s: String, k: Int): String = {
+    @tailrec // 这个函数已经优化成了尾递归
+    def reverse(s: String, needToReverse: Boolean, history: String): String = {
+      // 截取前k个字符（判断是否翻转）
+      val subStr = if (needToReverse) s.take(k).reverse else s.take(k)
+      // 如果字符串长度小于k，返回结果
+      // 否则，对于剩余字符串进行同样的操作
+      if (s.length < k) history + subStr
+      else reverse(s.drop(k), !needToReverse, history + subStr)
+    }
+    reverse(s, true, "")
+  }
+}
+```
+
 Rust:
 
 ```Rust