input: Write a function to convert a number into binary format. If the given number is 0, return '0'. Otherwise, return the binary representation of the number as a string.
  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(16) == '10000'
  assert convert_to_binary(31) == '11111'
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