foo.cc: In function ‘void Creeper::bfs()’:
foo.cc:21:51: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   21 |                                 for (int i = 0; i < s.size(); i++) {
      |                                                 ~~^~~~~~~~~~
foo.cc:22:63: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   22 |                                         for (int j = i + 1; j < s.size(); j++) {
      |                                                             ~~^~~~~~~~~~
foo.cc:46:51: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   46 |                                 for (int i = 0; i < s.size(); i++) {
      |                                                 ~~^~~~~~~~~~
foo.cc:58:38: warning: comparison of integer expressions of different signedness: ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} and ‘int’ [-Wsign-compare]
   58 |                         if (s.size() == maxx) continue;
      |                             ~~~~~~~~~^~~~~~~
foo.cc:72:43: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   72 |                         for (int i = 0; i < s.size(); i++) {
      |                                         ~~^~~~~~~~~~
foo.cc: In function ‘void Creeper::Kruskal()’:
foo.cc:101:27: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’ [-Wc++17-extensions]
  101 |                 for (auto [u, v, w]: e) {
      |                           ^