445. Add Two Numbers II

https://leetcode.com/problems/add-two-numbers-ii/
Python

# 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]:
        if not l1 and not l2:
            return ListNode(val=0)
        stack1, stack2 = [], []
        cur1, cur2 = l1, l2

        while cur1:
            stack1.append(cur1.val)
            cur1 = cur1.next

        while cur2:
            stack2.append(cur2.val)
            cur2 = cur2.next
        
        new_head = None
        carry = 0
        while stack1 or stack2 or carry:
            num1 = stack1.pop() if stack1 else 0
            num2 = stack2.pop() if stack2 else 0

            total = num1 + num2 + carry
            carry = total // 10
            
            new_node = ListNode(total % 10)
            new_node.next = new_head
            new_head = new_node

        return new_head
Python​

Python
