foo.cc: In member function ‘void PolyList::Select()’:
foo.cc:23:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<PolyListNode>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   23 |                 for(int i=0;i<x.size();i++)
      |                             ~^~~~~~~~~
foo.cc:26:40: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<PolyListNode>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   26 |                         for(int j=i+1;j<x.size();j++)
      |                                       ~^~~~~~~~~
foo.cc: In member function ‘void PolyList::Output()’:
foo.cc:65:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<PolyListNode>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   65 |                 for(int i=0;i<x.size();i++)
      |                             ~^~~~~~~~~