链表的Python总和

Question

These are my code

class Node():
'''A node in a linked list'''
    def __init__(self, data, next_node=None):
        self.data = data
        self.next_node = next_node


def sum(LL):

    head = LL

    # If Linked list is empty, return 0
    if (head.data is None or head.data == []):
        result = 0

    # If Linked List contain only 1 node then return it
    elif (head.next_node is None):
        result = head.data

    else:
        curr = head
        result = curr.data
        # If next is not None then add up to result
        while (curr.next_node is not None):
            curr = curr.next_node
            result += curr.data

    return result

Problem is at the end of the code

while (curr.next_node is not None):
    curr = curr.next_node
    result += curr.data

If i try this

LL = Node(1, Node(2, 3))
sum(LL)

I don't understand why it said

builtins.AttributeError: 'int' object has no attribute 'data'

The while loop works until it reach the last node

result should be 6

Answer 1

Because 3 is your next node. You probably wanted something like:

LL = Node(1, Node(2, Node(3)))

Answer 2

You are pointing to a node at the end which does not exist. The second nested node points to a next node 3, but that node does not exist sow hen it goes to look for its data, it is nowhere to be found.

Answer 3

How about a different approach; create an iterator to iterate through the linked list. Then you've got a standard iterator and you can just sum it with the builtin sum function:

def traverse(LL):
    head = LL
    while (head):
        yield head.data
        head = head.next_node


sum(traverse(LL))