#include <string>
#include "TFile.h"
#include "TTree.h"

void tree_str_test_3 () {
  TFile *f = new TFile("tree_str_test_3.root","recreate");
  TTree *t = new TTree("t","tree t");
  
  std::string str_1, str_2;
  
  t->Branch("str_1",&str_1);
  t->Branch("str_2",&str_2);
  
  str_1 = "aa1";
  str_2 = "aa2";
  t->Fill();

  str_1 = "bb1";
  str_2 = "bb2";
  t->Fill();

  str_1 = "aa1";
  str_2 = "bb2";
  t->Fill();

  f->Write();
}