2. Add Two Numbers.py

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


def addTwoNumbers(l1: ListNode, l2: ListNode) -> ListNode:
    d = n = ListNode(0)
    carry = 0
    while l1 or l2 or carry:
        if l1:
            carry += l1.val
            l1 = l1.next
        if l2:
            carry += l2.val
            l2 = l2.next

        d.next = ListNode(carry % 10)
        d = d.next
        carry //= 10
    return d.next


l1 = ListNode(9)
l1.next = ListNode(9)
l1.next.next = ListNode(9)
l1.next.next.next = ListNode(9)
l1.next.next.next.next = ListNode(9)
l2 = ListNode(9)
l2.next = ListNode(9)
l2.next.next = ListNode(9)
l2.next.next.next = ListNode(9)
l2.next.next.next.next = ListNode(9)
v = addTwoNumbers(l1, l2)
print(v.val)