#include <vector>
using std::vector;

#include <TCanvas.h>
#include <TBox.h>
#include <TLine.h>
#include <TRandom.h>

//------------------------------------------------------

int getIndexGrid2D(int i, int j, int nColumn)
// for a 2D grid, stored in an array, return the idx given by two indices
{
  int idx = j*nColumn+i;
  return idx;
}

//------------------------------------------------------

void DrawLattice(int length, float frac)
{

  // the square lattice
  TCanvas *c = new TCanvas("Lattice","Lattice",800,800);
  c->Range(-1,-1,length+1,length+1);

  TBox *bLattice = new TBox(0,0,length,length);
  bLattice->SetLineColor(kBlack);
  bLattice->SetLineWidth(2);
  bLattice->SetFillStyle(0);
  bLattice->Draw("l");

  // the grid
  for(int i=1;i<length;i++) {
    TLine *lh = new TLine(0,i,length,i);
    lh->SetLineWidth(1);
    lh->SetLineColor(18);
    lh->Draw();
    TLine *lv = new TLine(i,0,i,length);
    lv->SetLineWidth(1);
    lv->SetLineColor(18);
    lv->Draw();
  }

  // fill a fraction  with random boxes
  vector<int> grid(length*length,0);

  int nb = (int) (length*length*frac);
  int i=0;
  do {
    int x = (int) gRandom->Uniform(0,length);
    int y = (int) gRandom->Uniform(0,length);
    int idx = getIndexGrid2D(x,y,length);
    if (grid[idx]==1) continue;
    i++;
    grid[idx]=1;
    TBox *b = new TBox(x,y,x+1,y+1);
    b->SetFillColor(2);
    b->SetFillStyle(1001);
    b->Draw();
  } while (i<=nb);
  
}