Trying to add two linked lists together but getting an AttributeError

Question

I am trying to add two LinkedLists together but I keep receiving an error saying:

AttributeError: 'int' object has no attribute 'val'

I understand my code may be wrong algorithmically, but I cannot get around this one error. I have tried removing the .val but that throws a different error and I have printed l1.val and l2.val before the while loop and it prints without error. The following is the definition for the LinkedList class provided and my code.

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

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        output = ListNode(None)
        while l1:
            temp = l1.val + l2.val
            if temp > 9:
                temp -= 10
                l1 = l1.next.val + 1
            else:
                l1 = l1.next
            output.next = temp
            l2 = l2.next

Scott Hunter · Accepted Answer · 2020-03-19 16:25:14Z

2

temp is an int, but you assign it to output.next, which will cause the error you see when it is used as a ListNode.

answered Mar 19, 2020 at 16:25

Scott Hunter

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2 Comments

Scott Hunter Over a year ago

output.val = temp?

Shrey Over a year ago

Sorry for the confusion. I understand now. Thanks.

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