Leetcode 算法 － 2. Add Two Numbers

# 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
        """
        x1, x2 = l1, l2
        results = ListNode(0)
        p = results
        while True:
            if not x1 and not x2 and not p.next:
                break
        
            if p.next:
                c = getattr(x1, 'val', 0) + getattr(x2, 'val', 0) + flag.next.val
            else:
                c = getattr(x1, 'val', 0) + getattr(x2, 'val', 0)
        
            flag = ListNode(c % 10)
        
            if c >= 10:
                flag.next = ListNode(c / 10)
        
            p.next = flag
            p = flag
        
            x1 = x1.next if isinstance(x1, ListNode) else None
            x2 = x2.next if isinstance(x2, ListNode) else None
        
        return results.next