Compilare: user.cpp: In function ‘void BFS(int)’: user.cpp:24:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < a[k].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:37:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sate.in","r",stdin); ^ user.cpp:38:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sate.out","w",stdout); ^ user.cpp:42:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d",&N,&M,&X,&Y); ^ user.cpp:46:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d",&x,&y,&d); ^