AddTwoNumbers.py

'''
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 contains a single digit.
Add the two numbers and return the sum as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
'''

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def addTwoNumbers(self, l1, l2, c = 0):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        val = l1.val + l2.val + c
        c = val // 10
        ret = ListNode(val % 10)
    
        
        if(l1.next != None or l2.next != None or c != 0 ):
            if l1.next == None:
                l1.next = ListNode(0)
            if l2.next == None:
                l2.next = ListNode(0)
            ret.next = self.addTwoNumbers(l1.next,l2.next,c)
        return  ret
'''
Your input [2,4,3] [5,6,4]
Output
[7,0,8]
Expected
[7,0,8]
'''