input: from typing import List
  
  def convert_to_binary(num: int) -> str:
      """Convert a decimal number to its binary representation.
      >>> convert_to_binary(10)
      '1010'
      >>> convert_to_binary(0)
      '0'
      >>> convert_to_binary(1)
      '1'
      >>> convert_to_binary(42)
      '101010'
      """
      if num == 0:
          return '0'
      
      binary = ''
      
      while num != 0:
          remainder = num % 2
          binary = str(remainder) + binary
          num = num // 2
      
      return binary
output:     if num == 0:
          return '0'
      
      binary = ''
      
      while num != 0:
          remainder = num % 2
          binary = str(remainder) + binary
          num = num // 2
      
      return binary