How to get an array of cuts

ROOT
6

I think you should have a quick look at a C++ manual before writing your code. What you are asking is really the basis of the language. You should do:

if (cut[bin]->IsInside(Eout,Ein)) {
   hp[bin]->Fill(Eout,Ein);
   H=(m*Eout+b-Ein)/sqrt(1+m*m);
   Np[bin]->Fill(H);
}