Question

我正在Python 3.6.5中实现LinkedList。我一直坚持从头删除节点：

代码如下：

class Node(object):

def __init__(self, data):
    self.data = data
    self.nextNode = None

class LinkedList(object):

def __init__(self):
    self.head = None
    self.counter = 0

def print_list(self):
    current = self.head
    while current is not None:
        print(current.data)
        current = current.nextNode

def size(self):
    print(self.counter)

def insert_end(self,data):
    newNode = Node(data)
    current = self.head
    if self.head is None:
        self.head = newNode
        self.counter+=1
    else:
        while current.nextNode is not None:
            current = current.nextNode
        current.nextNode = newNode
        self.counter+=1

def insert_end(self,data):
    newNode = Node(data)
    current = self.head
    if self.head is None:
        self.head = newNode
        self.counter+=1
    else:
        while current.nextNode is not None:
            current = current.nextNode
        current.nextNode = newNode
        self.counter+=1

def insert_beg(self,data):
    newNode = Node(data)
    if self.head is None:
        self.head = newNode
        self.counter+=1
    else:
        newNode.nextNode = self.head
        self.head = newNode
        self.counter+=1

def remove_beg(self):
    if self.head is None:
        print("Linked List is already empty")
    else:
        currentNode = self.head
        self.head = self.head.nextNode
        self.counter-=1
        del currentNode

def remove_end(self):
    if self.head is None:
        print("Linked List is already empty")
    else:
        current_head = self.head
        while current_head.nextNode is not None:
            current_head = current_head.nextNode
        current_node = current_head
        current_head.nextNode = None
        del current_node.nextNode
        self.counter-=1


linkedlist = LinkedList()
linkedlist.remove_beg()
linkedlist.insert_end(1)
linkedlist.insert_end(2)
linkedlist.insert_end(3)
linkedlist.insert_end(4)
print("printing list")
linkedlist.print_list()
linkedlist.insert_beg(22)
print("printing list after addition of 22 in the beginning")
linkedlist.print_list()
linkedlist.remove_beg()
print("printing list")
linkedlist.print_list()
print("printing size")
linkedlist.size()
linkedlist.insert_end(55)
linkedlist.print_list()
linkedlist.remove_end()
linkedlist.print_list()

一切正常，除了从末端移除节点。

输出：

回溯（最近通话最近）：

中的文件“ intermediate.py”，第84行      linkedlist.remove_end（）
   在remove_end
的文件“ intermediate.py”的第61行      current_head.nextNode =无
  AttributeError：'NoneType'对象没有属性'nextNode'

Answer 1

要从最后一个节点删除节点，我们需要在倒数第二个节点和None之间创建链接

def remove_end(self):
    if self.head is None:
        print('List is empty!')
    else:
        current_head = self.head
        current_node = None
        while current_head.nextNode is not None:
            previous = current_head
            current_head = current_head.nextNode
        previous.nextNode = None
        del current_head

最后删除节点的Python链接列表

1 个答案: