应用于链表时，python中深层和浅层副本的区别是什么？

Question

当我尝试解决leetcode 19从最后删除第k个节点时，我发现了一个棘手的问题。我认为原因是我不太了解python的深层和浅层副本。谁能告诉我为什么我的版本2对所有测试用例都不起作用？

class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None


class Solution(object):
    def removeNthFromEnd(self, head, n):  //this is correct
        """
        :type head: ListNode
        :type n: int
        :rtype: ListNode
        """
        help=[]
        dummy=ListNode(None)
        dummy.next=head
        cur=dummy
        while cur:
            help.append(cur)
            cur=cur.next

        node=help[-n-1]
        node.next=node.next.next

        return dummy.next


    def removeNthFromEnd2(self, head, n):  //this is not correct when test case is head [1], n=1
        """
        :type head: ListNode
        :type n: int
        :rtype: ListNode
        """
        help=[]
        dummy=ListNode(None)
        dummy.next=head

        while dummy:
            help.append(dummy)
            dummy=dummy.next

        node=help[-n-1]
        node.next=node.next.next

        return head