Compilare: user.cpp: In function ‘void dfs2(int)’: user.cpp:22:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v2[k].size();++i) ^ user.cpp: In function ‘void dfs(int)’: user.cpp:34:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[k].size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:90:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<c[i].size();++j) ^ user.cpp:43:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("2sat.in", "r", stdin); ^ user.cpp:44:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("2sat.out", "w", stdout); ^ user.cpp:46:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i %i", &n, &m); ^ user.cpp:53:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i %i", &a, &b); ^