Compilare: user.cpp: In function ‘void DFS(int)’: user.cpp:55:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < G[node].size(); i++) ^ user.cpp: In function ‘void DFSrev(int)’: user.cpp:67:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < Grev[node].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:21:35: 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:22:37: 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:23:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:25:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^