"""

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 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.

My opinion:
I want to use less if statement.
"""
# 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:
        total = 0
        result = None
        node = None
        while l1 != None or l2 != None:
            # if l1 or l2 is not none, add value to total
            if l1 != None:
                total += l1.val
                l1 = l1.next
            if l2 != None:
                total += l2.val
                l2 = l2.next

            # val less than 10
            val = 0
            if total >= 10:
                val = total - 10
                total = 1
            else:
                val = total
                total = 0

            # make linked list
            if result == None:
                node = ListNode(val)
                result = node
            else:
                node.next = ListNode(val)
                node = node.next

        # last value
        if total != 0:
            if result == None:
                result = ListNode(total)
            else:
                node.next = ListNode(total)
        return result