@Override
void execute() {
CellCollection cells = getCells();
mOldNotes.clear();
for (int r = 0; r < CellCollection.SUDOKU_SIZE; r++) {
for (int c = 0; c < CellCollection.SUDOKU_SIZE; c++) {
Cell cell = cells.getCell(r, c);
mOldNotes.add(new NoteEntry(r, c, cell.getNote()));
cell.setNote(new CellNote());
CellGroup row = cell.getRow();
CellGroup column = cell.getColumn();
CellGroup sector = cell.getSector();
for (int i = 1; i <= CellCollection.SUDOKU_SIZE; i++) {
if (!row.contains(i) && !column.contains(i) && !sector.contains(i)) {
cell.setNote(cell.getNote().addNumber(i));
}
}
}
}
}
