foo.cc: In function ‘int main()’:
foo.cc:14:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   14 |     for (int j = 0; j < arr.size(); j++) {
      |                     ~~^~~~~~~~~~~~
foo.cc:15:29: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   15 |         for (int k = j+1; k < arr.size(); k++) {
      |                           ~~^~~~~~~~~~~~