字符串中的TOUPPER函数
std::string& str_toupper(std::string& s) {
std::transform(s.begin(), s.end(), s.begin(),
[](unsigned char c){ return ::toupper(c); } // correct
);
return s;
}
std::string& str_toupper(std::string& s) {
std::transform(s.begin(), s.end(), s.begin(),
[](unsigned char c){ return ::toupper(c); } // correct
);
return s;
}