老卫带你学---leetcode刷题(344. 反转字符串)

344. 反转字符串

问题：

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 s 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。

示例 1：

输入：s = ["h","e","l","l","o"]
输出：["o","l","l","e","h"]

示例 2：

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

提示：

1 <= s.length <= 105
s[i] 都是 ASCII 码表中的可打印字符

解决：

双指针 交换

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        l,r=0,len(s)-1
        while l<r:
            s[l],s[r]=s[r],s[l]
            l+=1
            r-=1