foo.cc: In function 'int SPFA()':
foo.cc:38:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<node>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |         for(int i = 0; i < v[tmp].size(); ++i) {
      |                        ~~^~~~~~~~~~~~~~~

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