foo.cc: In function 'int main(int, char**)':
foo.cc:51:23: warning: comparison of integer expressions of different signedness: 'long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |         for (i = 0; i < vtSet_C.size(); i++)
      |                     ~~^~~~~~~~~~~~~~~~
foo.cc: In function 'void DifferenceSet(std::vector<int>, std::vector<int>, std::vector<int>*)':
foo.cc:60:23: warning: comparison of integer expressions of different signedness: 'long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   60 |         for (i = 0; i < vtSet_A.size(); i++)
      |                     ~~^~~~~~~~~~~~~~~~
foo.cc:63:31: warning: comparison of integer expressions of different signedness: 'long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   63 |                 for (j = 0; j < vtSet_B.size(); j++)
      |                             ~~^~~~~~~~~~~~~~~~
foo.cc:68:23: warning: comparison of integer expressions of different signedness: 'long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |                 if (j == vtSet_B.size())
      |                     ~~^~~~~~~~~~~~~~~~~

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