class Solution {
public:
void swap(char &ch1, char &ch2){
}
/**
* 反转字符串
* @param str string字符串
* @return string字符串
*/
string solve(string str) {
// write code here
char ch;
int sz = str.size();
for(int i=0; i<sz-1-i; i++){
ch = str[i];
str[i] = str[sz-1-i];
str[sz-1-i] = ch;
}
return str;
}
};