[2]AddTwoNumbers.py

from typing import Optional


class ListNode:
    def __init__(self, val=0, next=None):
        self.value = val
        self.next = next

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        dummyHead = ListNode(0)
        tail = dummyHead
        carry = 0

        while l1 is not None or l2 is not None or carry != 0:
            digit1 = l1.val if l1 is not None else 0
            digit2 = l2.val if l2 is not None else 0

            sum = digit1 + digit2 + carry
            digit = sum % 10
            carry = sum // 10

            newNode = ListNode(digit)
            tail.next = newNode
            tail = tail.next

            l1 = l1.next if l1 is not None else None
            l2 = l2.next if l2 is not None else None
        
        result = dummyHead.next
        dummyHead.next = None
        return result
l1 = ListNode(2, ListNode(4, ListNode(3)))
l2 = ListNode(5, ListNode(6, ListNode(4)))
x = Solution().addTwoNumbers(l1 = l1, l2 = l2)
print(x.next.next.value)