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问题描述
所以我正在学习Python中的链接列表，但是在节点之间插入节点时遇到了麻烦.让我在下面发布我的代码，并解释我已经做过的事情以及我认为问题出在哪里.
So I'm learning Linked Lists in Python but having trouble inserting a node between my nodes. Let me post my code below and explain what I've done and where I believe the problem is happening.
class Node(object):
def __init__(self, data):
self.data = data
self.nextNode = None
'''
def __str__(self):
return str(self.data)
'''
class LinkedList(object):
def __init__(self):
self.head = None
self.tail = None
# Insert inbetween
def insert_in_between(self, data, prev_data):
print("<<< INSERT INBETWEEN >>>")
# instantiate the new node
new_node = Node(data)
print("This is new_node: ", new_node)
# assign to head
thisval = self.head
print("This is thisval: ", thisval)
print("This is prev_data: ", prev_data)
# check each value in linked list against prev_data as long as value is not empty
while thisval is not None:
print("thisval is NOT NONE")
print("in while loop, thisval = ", thisval)
print("in while loop, prev_data = ", prev_data)
# if value is equal to prev_data
if thisval == prev_data:
print("thisval == prev_data")
# make the next of new_node the prev_data's next
new_node.nextNode = prev_data.nextNode
# make the next of prev_data the new_node
prev_data.nextNode = new_node
break;
# if value is not eqaul to prev_data then assign variable to next Node
else:
thisval = thisval.nextNode
def push_from_head(self, NewVal):
new_node = Node(NewVal)
print("This is new_node: ", new_node.data)
last = self.head
print("This is last/HEAD: ", last)
if self.head is None:
print("Head is NONE")
self.head = new_node
print("This is self.head: ",self.head)
return
print("last.nextNode: ", last.nextNode)
while last.nextNode is not None:
print("this is last inside while loop: ", last.data)
print("last.nextNode is not NONE")
last = last.nextNode
print("This is the last last: ", last.data)
last.nextNode = new_node
print("This is last.nextNode: ", last.nextNode)
def print_nodes(self):
if self.head:
thisval = self.head
while thisval:
print("This is node: ", thisval.data)
thisval = thisval.nextNode
e1 = LinkedList()
e1.push_from_head(10)
e1.push_from_head(20)
e1.push_from_head(30)
e1.push_from_head(40)
e1.push_from_head(50)
e1.insert_in_between(25, 20)
e1.print_nodes()
- 好的，所以我想在20到30之间插入节点(25).
- 在我的方法insert_in_between中，我采用两个参数:data和prev_data.数据为25，但由于将其传递给Node类而成为Node?但是prev_data是int(20).
- 我期望这个打印语句在
thisval == prev_data时打印print("thisval == prev_data")，但我认为是因为节点和整数之间存在不匹配，那么该陈述将无法评估为真. - Ok, so I want to insert the node (25) in between 20 and 30.
- In my method insert_in_between I'm taking two arguments: data and prev_data. Data is 25, but becomes a Node because I'm passing it into a Node class? But prev_data is an int(20).
- I was expecting this print statment to print
print("thisval == prev_data")whenthisval == prev_databut I think because there a mismatch between nodes and ints, that statment won't evaluate to true.
我确信这是一个简单的解决方法，并且一直在尝试找到一个没有运气的解决方案.谁能指出我正确的方向?
I'm sure this is an easy fix and have been trying to work out a solution with no luck. Can anyone point me in the right direction?
编辑
当我按照建议将行更改为: if thisval.data == prev_data:时，我得到一个错误:AttributeError:'int'对象没有属性'nextNode'，它抱怨此行: new_node.nextNode = prev_data.nextNode
When I change the line as suggested to: if thisval.data == prev_data: I get an error: AttributeError: 'int' object has no attribute 'nextNode' where it complains about this line: new_node.nextNode = prev_data.nextNode
推荐答案
上述建议不太奏效.我必须添加一个名为getNodes()的新方法来获取节点的索引，以便可以在我的insert_in_between方法中调用它.
The above suggestion didn't quite work. I had to add a new method called getNodes() to get the index of the node so I can call it in my insert_in_between method.
class Node(object):
def __init__(self, data):
self.data = data
self.nextNode = None
class LinkedList(object):
def __init__(self):
self.head = None
self.tail = None
def getNode(self, index):
if self.head is not None:
current = self.head
count = 0
while(current):
if count == index:
return current;
else:
count+=1
current = current.nextNode
else:
print("There are no nodes")
# Insert inbetween
def insert_in_between(self, data, prev_data):
print("<<< INSERT INBETWEEN >>>")
# instantiate the new node
new_node = Node(data)
print("This is new_node: ", new_node)
# assign to head
thisval = self.head
print("This is thisval: ", thisval)
print("This is prev_data: ", prev_data)
prev_node = self.getNode(1)
print("This is prev_node: ", prev_node.data)
# check each value in linked list against prev_data as long as value is not empty
while thisval is not None:
print("thisval is NOT NONE")
print("in while loop, thisval = ", thisval)
print("in while loop, prev_data = ", prev_data)
# if value is equal to prev_node
if thisval.data == prev_node.data:
print("thisval == prev_node")
# make the next of new_node the prev_node's next
new_node.nextNode = prev_node.nextNode
# make the next of prev_node the new_node
prev_node.nextNode = new_node
break;
# if value is not eqaul to prev_data then assign variable to next Node
else:
thisval = thisval.nextNode
def push_from_head(self, NewVal):
new_node = Node(NewVal)
print("This is new_node: ", new_node.data)
last = self.head
print("This is last/HEAD: ", last)
if self.head is None:
print("Head is NONE")
self.head = new_node
print("This is self.head: ",self.head)
return
print("last.nextNode: ", last.nextNode)
while last.nextNode is not None:
print("this is last inside while loop: ", last.data)
print("last.nextNode is not NONE")
last = last.nextNode
print("This is the last last: ", last.data)
last.nextNode = new_node
print("This is last.nextNode: ", last.nextNode)
def print_nodes(self):
if self.head:
thisval = self.head
while thisval:
print("This is node: ", thisval.data)
thisval = thisval.nextNode
e1 = LinkedList()
e1.push_from_head(10)
e1.push_from_head(20)
e1.push_from_head(30)
e1.push_from_head(40)
e1.push_from_head(50)
e1.insert_in_between(25, 20)
e1.print_nodes()
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