foo.cc: In function ‘void dijkstra()’:
foo.cc:27:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<st>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   27 |                 for(int i=0;i<g[u].size();i++)
      |                             ~^~~~~~~~~~~~