foo.cc: In member function 'int BitSet::count()':
foo.cc:20:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |                 for (int i = 0; i < q.size(); i++)
      |                                 ~~^~~~~~~~~~
foo.cc: In member function 'bool BitSet::any()':
foo.cc:28:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |                 for (int i = 0; i < q.size(); i++)
      |                                 ~~^~~~~~~~~~
foo.cc: In member function 'unsigned int BitSet::to_ulong()':
foo.cc:60:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   60 |                 for (int i = 0; i < q.size(); i++)
      |                                 ~~^~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务