【发布时间】：2016-10-26 13:07:42
【问题描述】：
我想实现 5 种方法来删除单个链表中的节点。
删除列表中的第一个元素 - 简单
删除列表中的最后一个元素 - 简单
删除某个位置的元素（数字） - 简单
删除具有给定值的元素 - 简单
删除特定节点 - 不知道该怎么做
我猜我面临的挑战是如何找到节点的内存地址或如何将节点的内存地址传递给方法。以下是我想出的代码。显然 " def delete_node(self, node):" 不起作用。以下是我目前想出的代码。
from Node import Node
class SingleLinkedList:
"""Constructor. Sets the length of the linkedlist to zero and initializes head reference"""
def __init__(self):
self.head = None
self.length = 0
""" Method to get the length of the list """
def get_list_length(self):
return self.length
""" Method to INSERT a node at the beginning of the list """
def insert_at_beginning(self, data):
new_Node = Node()
new_Node.set_data(data)
if self.length == 0:
self.head = new_Node
else:
new_Node.set_next(self.head)
self.head = new_Node
self.length += 1
""" Method to INSERT a node at the end of the list """
def insert_at_end(self, data):
new_Node = Node()
new_Node.set_data(data)
if self.length == 0:
self.head = new_Node
else:
current = self.head
while current.has_next():
current = current.get_next()
current.set_next(new_Node)
self.length += 1
""" Method to INSERT a node at the given position, i.e. after postion - 1 . Position count start at 0 """
def insert_at_position(self, position, data):
if position > self.length or position < 0:
return None
else:
if position == 0:
self.insert_at_beginning(data)
else:
if position == self.length:
self.insert_at_end(data)
else:
new_Node = Node()
new_Node.set_data(data)
current = self.head
count = 0
while count < (position - 1):
current = current.get_next()
count += 1
new_Node.set_next(current.get_next())
current.set_next(new_Node)
self.length += 1
""" Method to INSERT a new node to the list. Default insertion at the end of the list """
def add(self, data):
self.insert_at_end(data)
""" Method to PRINT the elements of the list """
def print_list(self):
if self.length == 0:
return "Linked List is empty"
else:
current = self.head
while current.has_next():
print str(current.get_data()) + " ---> ",
current = current.get_next()
print str(current.get_data())
""" Method to DELETE the node at the beginning of the list """
def delete_at_beginning(self):
if self.length == 0:
return "List is empty"
else :
self.head = self.head.get_Next()
self.length -= 1
""" Method to DELETE the node at the end of the list """
def delete_at_end(self):
if self.length == 0:
return "List is empty"
else:
current = self.head
previous = None
while current.has_next():
previous = current
current = current.get_next()
previous.set_Next(None)
self.length -= 1
""" Method to DELETE a node at the given position, i.e. after postion - 1 . Position count start at 0 """
def delete_at_position(self, position):
if position > self.length or position < 0:
return "Position does not exist"
else:
if position == 0:
self.delete_at_beginning()
elif position == self.length:
self.delete_at_end()
else:
count = 0
current = self.head
previous = None
while count < position:
previous = current
current = current.get_next()
count += 1
previous.set_next(current.get_next())
self.length -= 1
""" Method to DELETE a node with a given value """
def delete_value(self, value):
if self.length == 0:
print " List is empty "
else:
current = self.head
previous = None
while current.has_next():
if current.get_data() == value:
break
previous = current
current = current.get_next()
if current.get_data() != value:
print "Item " + str(value) + " not in the list"
else:
previous.set_next(current.get_next())
self.length -= 1
def delete_node(self, node):
if self.length == 0:
print "List is empty"
else:
current = self.head
previous = None
found = False
while not found:
if current == node:
found = True
elif current is None:
print "Node not in the list"
return
else:
previous = current
current = current.get_next()
if previous is None:
self.head = current.get_next()
else:
previous.set_next(current.get_next())
self.length -= 1
def main():
l = SingleLinkedList()
print l.get_list_length()
l.add(1)
l.add(2)
l.add(3)
l.print_list()
l.insert_at_beginning(500)
l.insert_at_beginning(600)
l.insert_at_beginning(700)
l.print_list()
l.insert_at_position(3, 99999)
l.print_list()
l.delete_at_position(3)
l.print_list()
l.delete_value(500)
l.print_list()
nd = Node()
nd.set_data(2)
l.delete_node(nd)
l.print_list()
if __name__ == '__main__':
main()
我正在关注一本用 C++ 编写的关于数据结构的书，并将其翻译成 Python。我想在 C++ 中传递内存地址很容易，也许这在使用 Python 时不可行？
任何帮助将不胜感激。
谢谢
编辑： 我有另一个与这门课有关的挑战。我希望能够迭代地和递归地找到链表的长度/大小。迭代地查找长度是直截了当的。我如何递归地找到长度？我能够在脑海中想象递归方法，但无法用 Python 编写代码。此外，这很令人困惑，因为 self 是参数中的第一个方法。
def sizeByIteration(self):
current = self.head
counter = 0
while current is not None:
counter += 1
current = current.get_next()
return counter
# def sizeByRecursion(self):
# if self.head is None:
# return 0
# else:
# self.head = self.head.get_next()
# return 1 + self.sizeByRecursion()
【问题讨论】：
-
在一个位置删除我们可以改变链接，保持两个指针，说
p1=head,p2=head.next当p1到达你要删除的节点时改变p1.next=p2.next -
答案与 C++ 无关。 Pythonic 习语有很大的不同。
-
你的意思是
l.delete_node(nd)接近你的测试结束？这在 C++ 中也行不通。该节点根本不在列表中，因此无法从中删除。 -
你的代码应该等同于
delete_value(node.get_data())。忘记内存地址——你只是删除了传入的节点的值 -
如果无法从外部访问列表的节点，即使在 C++ 中也无法进行此操作。
标签： python data-structures linked-list singly-linked-list