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