Compilare: user.cpp: In function ‘void bfs(int)’: user.cpp:18:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[a].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:44:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<niv[i].size();j++)printf(" %d",niv[i][j]); ^ user.cpp:30:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nivele2.in","r",stdin); ^ 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("nivele2.out","w",stdout); ^ user.cpp:32:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^ user.cpp:35:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^