class Solution {
public:
    /**
     * 反转字符串
     * @param str string字符串 
     * @return string字符串
     */
    string solve(string str) {
        // write code here
        for(int i=0;i<str.length()/2;i++){
            char c=str[i];
            str[i]=str[str.length()-i-1];
            str[str.length()-i-1]=c;
        }
        return str;
    }
};