#include "TFile.h"
#include "TTree.h"
#include "TRandom.h"
class Detector {
   Int_t fNhit;   //Number of hits
   Double_t *fX;  //[fNhit] array of x coordinates
   Double_t *fY;  //[fNhit] array of y coordinates

public:
   Detector() {fNhit=0; fX=0; fY=0;}
   void Fill() {
      fNhit = Int_t(gRandom->Uniform(0,50));
      delete [] fX;
      delete [] fY;
      fX=fY=0;
      if (fNhit<=0) return;
      fX = new Double_t[fNhit];
      fY = new Double_t[fNhit];
      for (Int_t i=0;i<fNhit;i++) {
         fX[i] = gRandom->Gaus(0,1);
         fY[i] = gRandom->Gaus(0,1);
      }
   }
   virtual ~Detector() {delete [] fX; delete [] fY;}
};
void dethit() {
   TFile f("dethit.root","recreate");
   TTree *T = new TTree("T","Luiz tree");
   const Int_t ndet = 10;
   Detector *det[ndet];
   //create Tree branches
   char bname[20];
   for (Int_t i=0;i<ndet;i++) {
      det[i] = new Detector();
      sprintf(bname,"det%d",i);
      T->Branch(bname,"Detector",&det[i]);
   }
     
   //create some events
   for (Int_t event=0;event<1000;event++) {
      for (Int_t i=0;i<ndet;i++) {
         det[i]->Fill();
      }
      T->Fill();
   }
   T->Write();
   T->Print();
   delete T;
}