# 541. Reverse String II

**<font color=red>难度: Easy</font>**

## 刷题内容

> 原题连接

* https://leetcode.com/problems/reverse-string-ii/

> 内容描述

```
Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and left the other as original.
Example:
Input: s = "abcdefg", k = 2
Output: "bacdfeg"
Restrictions:
The string consists of lower English letters only.
Length of the given string and k will in the range [1, 10000]
```

## 解题方案

> 思路 1
******- 时间复杂度: O(N)******- 空间复杂度: O(N)******


```python
class Solution:
    def reverseStr(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        lst = list(s)
        for i in range(0, len(lst), 2 * k):
            lst[i:i+k] = lst[i:i+k][::-1]
        return ''.join(lst)
```
