foo.cc: In function 'void spfa(int)':
foo.cc:44:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<node>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |                 for(int i=0; i<e[u].size(); i++)
      |                              ~^~~~~~~~~~~~

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