Compilare: user.cpp: In function ‘void topo_sort(std::vector<int>&, int)’: user.cpp:33:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < rev_gr[node].size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:74:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < res.size() - 1; ++i) ^