Compilare: user.cpp: In function ‘void BFS(int)’: user.cpp:20:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i <G[b].size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:31:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.in","r",stdin); ^ user.cpp:32:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.out","w",stdout); ^ user.cpp:33:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&t); ^ user.cpp:37:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&n,&m); ^ user.cpp:39:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&x,&y); ^