Compilare: user.cpp: In function ‘void nivel(int, int)’: user.cpp:15:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<L[x].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:36:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<N[i].size(); j++) ^