字符串逆序

题目：

Write a function that takes a string as input and returns the string reversed.
Example:
Given s = "hello", return "olleh".

思路：首尾字符交换

c++代码：

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