題目：反轉字符串

方法1：

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

方法2：

class Solution {
public:string reverseString(string s) {reverse(s.begin(), s.end());return s;}
};

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