/in/foo.cc: In function 'int main()':
/in/foo.cc:15:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |   for (i = 0; i < s.length() && flag; i++)
      |               ~~^~~~~~~~~~~~
/in/foo.cc:17:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |    for (j = 0; j < s.length(); j++)
      |                ~~^~~~~~~~~~~~
/in/foo.cc:20:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |    if (j == s.length())
      |        ~~^~~~~~~~~~~~~
/in/foo.cc:28:3: error: 'reverse' was not declared in this scope
   28 |   reverse(s.begin(), s.end());
      |   ^~~~~~~
/in/foo.cc:30:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |   for (i = 0; i < s.length() && flag; i++)
      |               ~~^~~~~~~~~~~~
/in/foo.cc:32:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |    for (j = 0; j < s.length(); j++)
      |                ~~^~~~~~~~~~~~
/in/foo.cc:35:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   35 |    if (j == s.length())
      |        ~~^~~~~~~~~~~~~