Compilare: user.cpp: In function ‘void predf(int)’: user.cpp:16:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp: In function ‘void ancestors(int, int)’: user.cpp:35:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp: In function ‘void df(int)’: user.cpp:47:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp: In function ‘int num_ops(int)’: user.cpp:57:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < sorted.size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:68:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arborest.in", "r", stdin); ^ user.cpp:69:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arborest.out", "w", stdout); ^ user.cpp:71:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &k); ^ user.cpp:74:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &F[i]); ^