Compilare: user.cpp: In function ‘void mark(int)’: user.cpp:29:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int B=0; B<a[A].size(); B++){ ^ user.cpp:37:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<a[target].size(); j++){ ^ user.cpp: In function ‘void bfs()’: user.cpp:57:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a[x].size(); i++){ ^