LeetCode: 344 Reverse String

题目：

Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

 代码：

 自己的：

class Solution {
public:
    string reverseString(string s) {
        stack<char> tem;
        string result;
        for ( auto c : s)
            tem.push(c);
        while (!tem.empty()){
            result += tem.top();
            tem.pop();
        }
        return result;
    }
};

别人的：

class Solution {
public:
    string reverseString(string s) {
        if (s.size() < 2)
            return s;
        int l = 0, r = static_cast<int>(s.size() - 1);
        while (l < r)
        {
                swap(s[l++], s[r--]);
        }
        return s;
    }
};

别人的效率好。

swap()函数：交换