leetcode344. 反转字符串

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"]

class Solution {
public:
     void reverseString(vector& s)
    {
        helper(s,0,s.size());
    }
    void helper(vector& s, int pos, int s_len)
    {
        if (pos >= s_len/2) return;
        char tmp = s[pos];
        s[pos] = s[s_len-1-pos];
        s[s_len-1-pos] = tmp;

        helper(s,pos+1,s_len);
    }
};

python 版本

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