def reverseLink(head: ListNode) -> ListNode:
if not head or not head.next:
return head
node = reverseLink(head.next)
head.next.next = head
head.next = None
return node
def reverseList(self, head: ListNode) -> ListNode:
if not head or not head.next:
return head
node = self.reverseList(head.next)
head.next.next = head
head.next = None
return node
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
if not l1 and not l2:
return None
if not l2:
l2 = ListNode(0)
if not l1:
l1 = ListNode(0)
l1.val = l1.val + l2.val
if l1.val > 9:
l1.val = l1.val - 10
if l1.next:
l1.next.val += 1
else:
l1.next = ListNode(1)
l1.next = self.addTwoNumbers(l1.next, l2.next)
return l1
