new_contents: """Leetcode 415. Add Strings
  Easy
  
  URL: https://leetcode.com/problems/add-strings/
  
  Given two non-negative integers num1 and num2 represented as string,
  return the sum of num1 and num2.
  
  Note:
  - The length of both num1 and num2 is < 5100.
  - Both num1 and num2 contains only digits 0-9.
  - Both num1 and num2 does not contain any leading zero.
  - You must not use any built-in BigInteger library or convert the inputs to 
    integer directly.
  """
  
  class Solution(object):
      def addStrings(self, num1, num2):
          """
          :type num1: str
          :type num2: str
          :rtype: str
          """
          pass
  
  
  def main():
      pass
  
  
  if __name__ == '__main__':
      main()
  
subject: Add lc0415_add_strings.py