Write a function that reverses a string. The input string is given as an array of characters s.

You must do this by modifying the input array in-place with O(1) extra memory.

Example 1:

Input: s = [“h”,“e”,“l”,“l”,“o”]
Output: [“o”,“l”,“l”,“e”,“h”]

Example 2:

Input: s = [“H”,“a”,“n”,“n”,“a”,“h”]
Output: [“h”,“a”,“n”,“n”,“a”,“H”]
https://leetcode.cn/problems/reverse-string/solutions/2376290/ji-chong-bu-tong-de-xie-fa-pythonjavacgo-9trb/
思路一：快慢指针

class Solution:
    def reverseString(self, s: List[str]) -> None:
        left = 0
        right = len(s) - 1
        while left < right:
            s[left], s[right] = s[right], s[left]
            left += 1
            right -= 1

思路二：循环

class Solution:
    def reverseString(self, s: List[str]) -> None:
        for i in range(len(s) // 2):
            s[i], s[-i - 1] = s[-i - 1], s[i]

思路三：使用语法糖

class Solution:
    def reverseString(self, s: List[str]) -> None:
        # s[:] = s[::-1] 是切片赋值语法，表示用 s[::-1] 替换 s 中的元素。
        # 注意不能写成 s = s[::-1]，因为 s 只是形参，修改 s 不会影响函数外部传入的实参。
        # 注意这不是原地操作，需要 O(n) 额外空间。
        s[:] = s[::-1]