for(int i=0; i<v.size(); i++)
for(int j=0; j<v[i].size(); j++)
cout<<v[i][j]<<" ";
cout<<endl;
for(auto lst : vec){
for(auto e : lst){
cout<<e<<" ";
}
cout<<endl;
}
for( auto &row : arr) {
for(auto col : row)
cout << col << " ";
cout<<endl;
}