/in/foo.cc: In function 'int main(int, char**)':
/in/foo.cc:47:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < vtSet_C.size(); i++)
              ~~^~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void DifferenceSet(std::vector<int>, std::vector<int>, std::vector<int>*)':
/in/foo.cc:55:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < vtSet_A.size(); i++)
              ~~^~~~~~~~~~~~~~~~
/in/foo.cc:58:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (j = 0; j < vtSet_B.size(); j++)
               ~~^~~~~~~~~~~~~~~~
/in/foo.cc:54:42: warning: unused variable 'nIndex' [-Wunused-variable]
  int i, j, nSelectElement = 0, nTag = 0, nIndex = 0;
                                          ^~~~~~