LeetCode 2. Add Two Numbers

Description

　　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:

　　Input: (2 -> 4 - > 3) + (5 -> 6 - > 4)

　　Output: 7 -> 0 - > 8

　　Explanation: 342 + 465 = 807.

Python code

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        carry = 0 
        head = ListNode(0)
        currentNode = head
        while l1 or l2:
            if l1:
                carry += l1.val
                l1 = l1.next
            if l2:
                carry += l2.val
                l2 = l2.next
                
            currentNode.next = ListNode(carry%10)
            currentNode = currentNode.next
            carry = carry//10
            
        if carry == 1:
            currentNode.next = ListNode(1)
            currentNode = currentNode.next
        return head.next