344. 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 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

方法一：双指针

 1 /**
 2  * @param {character[]} s
 3  * @return {void} Do not return anything, modify s in-place instead.
 4  */
 5 var reverseString = function(s) {
 6     const n =s.length;
 7     for(let left =0,right=n-1;left<right;++left,--right){
 8         [s[left],s[right]]=[s[right],s[left]];
 9     }
10 };