难度：简单

知识点：双指针、字符串

地址：https://leetcode-cn.com/problems/reverse-string

编写一个函数，其作用是将输入的字符串反转过来。输入字符串以字符数组 char[] 的形式给出。

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"]

思路

from typing import *
class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        i, j = 0, len(s) - 1
        while i < j:
            if s[i] != s[j]:
                t = s[i]
                s[i] = s[j]
                s[j] = t
            i += 1
            j -= 1

s = Solution()
arr = ["h","e","l","l","o"]
s.reverseString(arr)
assert arr == ["o","l","l","e","h"]
arr = ["H","a","n","n","a","h"]
s.reverseString(arr)
assert arr == ["h","a","n","n","a","H"]