new_contents: #Codeing by Utf-8
  # Definition for singly-linked list.
  # class ListNode(object):
  #     def __init__(self, x):
  #         self.val = x
  #         self.next = None
  
  class Solution(object):
      def addTwoNumbers(self, l1, l2):
          """
          :type l1: ListNode
          :type l2: ListNode
          :rtype: ListNode
          """
          head = ListNode(0)
          current = head
          carry = 0
          while l1 is not None or l2 is not None or carry != 0:
              a = 0
              if l1 is not None:
                  a = l1.val
                  l1 = l1.next
              b = 0
              if l2 is not None:
                  b = l2.val
                  l2 = l2.next
              x = a + b + carry
              if x >= 10:
                  x -= 10
                  carry = 1
              else:
                  carry = 0
              current.next = ListNode(x)
              current = current.next
          return head.next
  
subject: Create Add-two-Numbers.py