input: Write a function to determine if a given number's digits can be rearranged to form a non-decreasing sequence. If it is possible, return True, otherwise return False. If the number is 0 or has no digits, return True.
  assert can_be_non_decreasing(6342)==True
  assert can_be_non_decreasing(3142)==True
  assert can_be_non_decreasing(9876)==False
  assert can_be_non_decreasing(112233)==True
  assert can_be_non_decreasing(0)==True
output: def can_be_non_decreasing(num):
      if num == 0:
          return True
      digits = list(str(num))
      digits.sort()
      for i in range(len(digits) - 1):
          if digits[i] > digits[i + 1]:
              return False
      return True