/in/foo.cc: In function 'void turn(std::string&)':
/in/foo.cc:6:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    6 |  for (int i = 0;i < s.length() / 2;i++)
      |                 ~~^~~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:27:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |    for (int i = tempb; i < num.length(); i++)
      |                        ~~^~~~~~~~~~~~~~
/in/foo.cc:26:8: warning: unused variable 'templen' [-Wunused-variable]
   26 |    int templen = num.length() - ans.length();
      |        ^~~~~~~
/in/foo.cc:34:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |   for (int i = 0; i < num.length(); i++)              //模拟求和（求和和进位必须分开！因为循环的次数不一样！）
      |                   ~~^~~~~~~~~~~~~~
/in/foo.cc:40:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |   for (int i = 0; i < ans.length(); i++)
      |                   ~~^~~~~~~~~~~~~~