/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/Geometry/CaloTopology/src/CaloSubdetectorTopology.cc

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#include "Geometry/CaloTopology/interface/CaloSubdetectorTopology.h"
#include <cassert>

std::vector<DetId> CaloSubdetectorTopology::getWindow(const DetId& id, const int& northSouthSize, const int& eastWestSize) const
{
  
  std::vector<DetId> cellsInWindow;
  // check pivot
  if (id.null())
    return cellsInWindow;

  //
  DetId myTmpId(id);
  std::vector<std::pair<Coordinate,DetId> > fringe;
  fringe.push_back(std::pair<Coordinate,DetId>(Coordinate(0,0),myTmpId));
  
  int halfWestEast = eastWestSize/2 ;
  int halfNorthSouth = northSouthSize/2 ;

  std::vector<CellInfo> visited_cells;
  visited_cells.resize(northSouthSize * eastWestSize);
  
  while (fringe.size() > 0)
    {
      std::pair<Coordinate,DetId> cur = fringe.back();
      fringe.pop_back();
      
      // check all four neighbours
      const CaloDirection directions[4] = { NORTH, SOUTH, EAST, WEST };
      
      for (unsigned dirnum = 0; dirnum < 4; ++dirnum)
        {
          Coordinate neighbour = getNeighbourIndex(cur.first,directions[dirnum]);
          //If outside the window range
          if ( neighbour.first < -halfWestEast ||
               neighbour.first > halfWestEast ||
               neighbour.second < -halfNorthSouth ||
               neighbour.second > halfNorthSouth )
            continue;
          
          
          //Found integer index in the matrix
          unsigned int_index =  neighbour.first + halfWestEast +  
            eastWestSize * (neighbour.second + halfNorthSouth );
          assert(int_index < visited_cells.size());
          
          // check whether we have seen this neighbour already
          if (visited_cells[int_index].visited)
            // we have seen this one already
            continue;
              
          // a new cell, get the DetId of the neighbour, mark it
          // as visited and add it to the fringe
          visited_cells[int_index].visited = true;
          std::vector<DetId> neighbourCells = getNeighbours(cur.second,directions[dirnum]);

          if ( neighbourCells.size() == 1 )
            visited_cells[int_index].cell = neighbourCells[0];
          else if ( neighbourCells.size() == 0 )
            visited_cells[int_index].cell = DetId(0);
          else
            throw cms::Exception("getWindowError") << "Not supported subdetector for getWindow method";
          
          if (!visited_cells[int_index].cell.null())
            fringe.push_back(std::pair<Coordinate,DetId>(neighbour,visited_cells[int_index].cell));
                  
        } // loop over all possible directions
    } // while some cells are left on the fringe
  
  
  for (unsigned int i=0; i<visited_cells.size(); i++)
    if (!visited_cells[i].cell.null())
      cellsInWindow.push_back(visited_cells[i].cell);
  
  return cellsInWindow;
}