2. Add Two Numbers - LeetCode

from typing import Optional, Self


# Definition for singly-linked list.
class ListNode:
    def __init__(self, val=0, next: Optional[Self] = None):
        self.val = val
        self.next = next


class Solution:
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        dummy = ListNode()
        h, c = dummy, 0
        while l1 or l2:
            v = (l1.val if l1 else 0) + (l2.val if l2 else 0)
            c, r = divmod(v + c, 10)
            h.next = ListNode(r)
            h = h.next
            l1 = l1.next if l1 else None
            l2 = l2.next if l2 else None
        if c:
            h.next = ListNode(c)
        return dummy.next