2. Add Two Numbers

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 contains a single digit. Add the two numbers and return the sum as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example 1:

Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.

Example 2:

Input: l1 = [0], l2 = [0]
Output: [0]

Example 3:

Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]

def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
	dummy_head = ListNode(0)
	current = dummy_head
	carry = 0
	
	while l1 or l2 or carry:
		val1 = l1.val if l1 else 0
		val2 = l2.val if l2 else 0
		
		total = val1 + val2 + carry
		carry = total // 10
		current.next = ListNode(total % 10)
		
		current = current.next
		if l1: l1 = l1.next
		if l2: l2 = l2.next
	
	return dummy_head.next