foo.cc: In member function 'void SeqList::Output()':
foo.cc:29:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |                 for(int i=0;i<data.size();++i)
      |                             ~^~~~~~~~~~~~