python 字符串反转

不要给另外的数组分配额外的空间，你必须原地修改输入数组、使用 O(1) 的额外空间解决这一问题。

你可以假设数组中的所有字符都是 ASCII 码表中的可打印字符。

示例 1：

输入：["h","e","l","l","o"]
输出：["o","l","l","e","h"]
示例 2：

输入：["H","a","n","n","a","h"]
输出：["h","a","n","n","a","H"]

　　

class Solution:

    def reverseString(self, li):
        """
        Do not return anything, modify s in-place instead.
        """
        start, end = 0, len(li) - 1
        while start < end:
            li[start], li[end] = li[end], li[start]
            start += 1
            end -= 1
        return li