input: Write a function to convert a number into its binary format. If the given number is 0, return the string "0".
  def convert_to_binary(num):
      if num == 0:
          return "0"
      binary = ''
      while num != 0:
          remainder = num % 2
          binary = str(remainder) + binary
          num = num // 2
      return binary
  assert convert_to_binary(10) == "1010"
  assert convert_to_binary(0) == "0"
  assert convert_to_binary(7) == "111"
  assert convert_to_binary(255) == "11111111"
  assert convert_to_binary(42) == "101010"
output: def convert_to_binary(num):
      if num == 0:
          return "0"
      binary = ''
      while num != 0:
          remainder = num % 2
          binary = str(remainder) + binary
          num = num // 2
      return binary