Compilare: user.cpp: In function ‘int main()’: user.cpp:36:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < G[i].size(); ++ j) ^ user.cpp:45:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < V.size(); i += 2) printf("%i %i\n", V[i].first, V[i].second); ^ user.cpp:13:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fenrir.out", "w", stdout); ^