逆转字符串Reverse String

​​https://leetcode.com/problems/reverse-string/​​

class Solution {
public:
    string reverseString(string s) {
        int len = s.size();
        if (len <= 1){
            return s;
        }

        int i = 0, j = len - 1;
        while (i < j){
            swap(s[i], s[j]);
            i++;
            j--;
        }
        return s;
    }
};