2. Add Two Numbers

#coding: utf-8

"""
2. Add Two Numbers

You are given two non-empty linked lists representing 
two non-negative integers. The digits are stored in 
reverse order and each of their nodes contain a single digit. 
Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, 
except the number 0 itself.

Example

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
"""
# 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
        """
        node = ListNode(0)
        tmp_node = node
        while l1 != None or l2 != None:
            n1 = l1.val if l1 != None else 0
            n2 = l2.val if l2 != None else 0
            add = tmp_node.next.val if tmp_node.next != None else 0
            n = (n1 + n2 + add) % 10
            add = (n1 + n2 + add) / 10
            t_node = ListNode(n)
            tmp_node.next = t_node
            tmp_node = t_node
            if add > 0:
                tmp_node.next = ListNode(add)
            l1 = l1.next if l1 != None else None
            l2 = l2.next if l2 != None else None
        return node.next