input: Write a python function to create an n x n array filled with zeros.
  assert get_array(3) == [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
  assert get_array(1) == [[0]]
  assert get_array(5) == [[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
output: def get_array(n):
      return [[0 for _ in range(n)] for _ in range(n)]