Compilare: user.cpp: In function ‘void bfs(int)’: user.cpp:22:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[el].size();++i) ^ user.cpp: In function ‘void bfs2(int)’: user.cpp:38:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[el].size();++i) ^