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 contain a single digit. Add the two numbers and return it as a linked list.

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

Example 1:

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

Example 2:

``````Input: l1 = , l2 = 
Output: 
``````

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]
``````

Constraints:

• The number of nodes in each linked list is in the range `[1, 100]`.
• `0 <= Node.val <= 9`
• It is guaranteed that the list represents a number that does not have leading zeros.
 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 `````` ``````# Definition for singly-linked list. # class ListNode: # def __init__(self, val=0, next=None): # self.val = val # self.next = next class Solution: def addTwoNumbers( self, l1: Optional[ListNode], l2: Optional[ListNode] ) -> Optional[ListNode]: dummy = ListNode(0) tail = dummy carry = 0 while l1 or l2: num1 = l1.val if l1 else 0 num2 = l2.val if l2 else 0 s = num1 + num2 + carry carry = s // 10 tail.next = ListNode(s % 10) tail = tail.next if l1: l1 = l1.next if l2: l2 = l2.next if carry: tail.next = ListNode(carry) return dummy.next``````
 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 `````` ``````type ListNode struct { Val int Next *ListNode } func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode { head := &ListNode{0, nil} result := head carry := 0 for l1 != nil || l2 != nil { temp := carry if l1 != nil && l2 != nil { temp += l1.Val + l2.Val } else if l1 != nil { temp += l1.Val } else { temp += l2.Val } head.Next = &ListNode{temp % 10, nil} carry = temp / 10 if l1 != nil { l1 = l1.Next } if l2 != nil { l2 = l2.Next } head = head.Next } if carry > 0 { head.Next = &ListNode{carry, nil} } return result.Next }``````