foo.cc: In function ‘int main()’:
foo.cc:8:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    8 |     for (int i = 0; i < s1.length(); i++)
      |                     ~~^~~~~~~~~~~~~
foo.cc:12:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   12 |     for (int i = 0; i < s2.length(); i++)
      |                     ~~^~~~~~~~~~~~~
foo.cc:54:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   54 |     for (int i = 0; i < ans.size(); i++)
      |                     ~~^~~~~~~~~~~~