Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:162:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (A[node]->size() != sa) cerr << "err\n"; ^ user.cpp:163:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (B[node]->size() != sb) cerr << "err\n"; ^ user.cpp:164:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (C[node]->size() != sc) cerr << "err\n"; ^ user.cpp: In function ‘int main()’: user.cpp:175:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("comp.in","r",stdin); ^ user.cpp:176:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("comp.out","w",stdout); ^ user.cpp:178:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:180:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^