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

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

 

Example 1:

Input: ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]

Example 2:

Input: ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]

加速一点点？双指针除二

class Solution {
public:
    void reverseString(vector<char>& s) {
        for(int i=0;i<s.size()/2;i++){
            char t=s[i];
            s[i]=s[s.size()-1-i];
            s[s.size()-1-i]=t;
        }
    }
};