Compilare: user.cpp: In function ‘void ctc(int)’: user.cpp:19:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < l[v].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:57:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < C.size(); i++) ^ user.cpp:58:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < C[i].size(); j++) ^ user.cpp:40:32: 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:41:34: 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:42:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:46:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &a, &b); ^