foo.cc: In member function 'int SeqList::Search(int)':
foo.cc:17:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |                 for (int i = 0; i < seq.size(); i++)
      |                                 ~~^~~~~~~~~~~~
foo.cc: In member function 'std::vector<int> SeqList::Union(SeqList&)':
foo.cc:38:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |                 for (int i = 0; i < obj.seq.size(); i++)
      |                                 ~~^~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:63:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   63 |         for (int i = 0; i < res.size(); i++)
      |                         ~~^~~~~~~~~~~~