Compilare: user.cpp: In function ‘int bfs()’: user.cpp:31:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<a[x].size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:57:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<a[n].size();i++) ^