实例讲述了Python数据结构与算法之链表定义与用法。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
（1）从链表节点的定义开始，以类的方式，面向对象的思想进行链表的设计文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
（2）链表类插入和删除等成员函数实现时需要考虑的边界条件，
prepend（头部插入）、pop（头部删除）、append（尾部插入）、pop_last（尾部删除）文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
2.1 插入：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
空链表
链表长度为1
插入到末尾文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
2.2 删除文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
空链表
链表长度为1
删除末尾元素文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
（3）从单链表到单链表的一众变体：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
带尾节点的单链表
循环单链表
双链表文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
1. 链表节点的定义文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
class LNode: def __init__(self, elem, next_=None): self.elem = elem self.next = next_
2. 单链表的实现文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
重点理解插入、删除的实现及其需要考虑的边界条件：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
class LinkedListUnderflow(ValueError):
pass
class LList:
def __init__(self):
self._head = None
def is_empty(self):
return self._head is None
def prepend(self, elem):
self._head = LNode(elem, self._head)
def pop(self):
if self._head is None:
raise LinkedListUnderflow('in pop')
e = self._head.elem
self._head = self._head.next
return e
def append(self, elem):
if self._head is None:
self._head = LNode(elem)
return
p = self._head
while p.next is not None:
p = p.next
p.next = LNode(elem)
def pop_last(self):
if self._head is None:
raise LinkedListUnderflow('in pop_last')
p = self._head
if p.next is None:
e = p.elem
self._head = None
return e
while p.next.next is not None:
p = p.next
e = p.next.elem
p.next = None
return e
简单总结：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
（0）能够访问 p.next.next 的前提是 p.next 不为空；
（1）尾部插入，如果链表不为空，需且仅需改变的是尾部节点的指针；
（2）尾部删除，如果链表长度不为空，需且仅需改变的是倒数第二个节点的指针。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
单链表的简单变形：具有尾部节点的单链表文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
class LList1(LList): def __init__(self): LList.__init__(self) self._rear = None ...
我们仅需重写的是：头部的插入、尾部的插入、尾部的删除文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
def prepend(self, elem):
if self._head is None:
self._head = LNode(elem)
self._rear = self._head
else:
self._head = LNode(elem, self._head)
def append(self, elem):
if self._head is None:
self._head = LNode(elem)
self._rear = self._head
else:
self._rear.next = LNode(elem)
self._rear = self._rear.next
def pop_last(self):
if self._head is None:
raise LinkedListUnderflow('in pop_last')
p = self._head
if p.next is None:
e = p.elem
self._head = None
return e
while p.next.next is not None:
p = p.next
e = p.next.elem
self._rear = p
p.next = None
return e
单链表的变体：循环单链表文章源自菜鸟学院-https://www.cainiaoxueyuan.com/suanfa/9662.html
class LCList:
def __init__(self):
self._rear = None
def prepend(self, elem):
if self._rear is None:
self._rear = LNode(elem)
self._rear.next = self._rear
else:
self._rear.next = LNode(elem, self._rear.next)
def append(self, elem):
self.prepend(elem)
self_rear = self._rear.next
def pop(self):
if self._rear is None:
raise LinkedListUnderflow('in pop')
p = self._rear.next
if p is None:
self._rear = None
else:
self._rear.next = p.next
return p.elem
def printall(self):
if self._rear is None:
raise ...
p = self._rear.next
while True:
print(p.elem)
if p is self._rear:
break
p = p.next