Compilare: user.cpp: In function ‘void dfnodes(int)’: user.cpp:22:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < fiu[n].size(); i++) ^ user.cpp: In function ‘void df(int, int)’: user.cpp:43:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < fiu[n].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:82:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < mut[t].size(); i++) ^ user.cpp:100:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < mut[i].size(); j++) ^ user.cpp:50:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("optic.in", "r", stdin); ^ user.cpp:52:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:56:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &i, &j); ^ user.cpp:91:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("optic.out", "w", stdout); ^