foo.cc: In function ‘int main()’:
foo.cc:44:10: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘std::priority_queue<int>::size_type’ {aka ‘long unsigned int’} [-Wformat=]
   44 | printf("%d",q.size/*返回优先队列中的元素个数*/());
      |         ~^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |          |                                    |
      |          int                                  std::priority_queue<int>::size_type {aka long unsigned int}
      |         %ld