1.基础类型转为字符串 api: std::to_string Defined in header std::string to_string( int value ); (1) (since C++11) std::string to_string( long value ); (2) (since C++11) std::string to_string( long long value ); (3) (since C++11) std::string to_string( unsigned value ); (4) (since C++