## Problem Statement

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 -> 8Explanation:342 + 465 = 807.

**Solution:**

# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution:
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
dummy_head = ListNode(0)
l3 = dummy_head
carry=0
while l1!=None or l2!=None:
l1_value = l2_value = 0
if l1!=None:
l1_value = l1.val
if l2!=None:
l2_value = l2.val
current_sum = l1_value + l2_value + carry
carry = current_sum//10
last_digit = current_sum%10
new_node = ListNode(last_digit)
l3.next = new_node
if l1!=None:
l1=l1.next
if l2!=None:
l2=l2.next
l3=l3.next
if carry>0:
new_node = ListNode(carry)
l3.next = new_node
l3 = l3.next
return dummy_head.next