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# Question:

# 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.
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# 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
        """
        return self.addList(l1, l2, 0)
            
        
    def addList(self, l1, l2, c):
        if not l1 and not l2:
            if c == 0:
                return None
            return ListNode(c)
        i = j = 0
        if l1:
            i = l1.val
            l1 = l1.next
        if l2:
            j = l2.val
            l2 = l2.next
        s = i + j + c
        c = int(s / 10)
        s = s % 10
        r = ListNode(s)
        r.next = self.addList(l1, l2, c)
        return r
        