def neighbors( open_list=[], closed_list=[] )
      i,j = free_cell      
      up = moved_matrix_with_parent(i, j, i-1, j, open_list, closed_list)
      down = moved_matrix_with_parent(i, j, i+1, j, open_list, closed_list)
      left = moved_matrix_with_parent(i, j, i, j-1, open_list, closed_list)
      right = moved_matrix_with_parent(i, j, i, j+1, open_list, closed_list)

      moved = []
      moved << up if !up.nil? 
      moved << down if !down.nil? 
      moved << left if !left.nil? 
      moved << right if !right.nil? 

      return moved
    end
def neighbors( open_list=[], closed_list=[] )
      i,j = free_cell      
      up = moved_matrix_with_parent(i, j, i-1, j, open_list, closed_list)
      down = moved_matrix_with_parent(i, j, i+1, j, open_list, closed_list)
      left = moved_matrix_with_parent(i, j, i, j-1, open_list, closed_list)
      right = moved_matrix_with_parent(i, j, i, j+1, open_list, closed_list)

      moved = []
      moved << up if !up.nil? 
      moved << down if !down.nil? 
      moved << left if !left.nil? 
      moved << right if !right.nil? 

      return moved
    end
Get all possible movement matrixes