Python数据结构之双向链表的定义与使用方法示例

本文实例讲述了Python数据结构之双向链表的定义与使用方法。分享给大家供大家参考，具体如下：

和单链表类似，只不过是增加了一个指向前面一个元素的指针而已。

示意图：

python 实现代码：

#!/usr/bin/python
# -*- coding: utf-8 -*-
class Node(object):
  def __init__(self,val,p=0):
    self.data = val
    self.next = p
    self.prev = p
class LinkList(object):
  def __init__(self):
    self.head = 0
  def __getitem__(self, key):
    if self.is_empty():
      print 'linklist is empty.'
      return
    elif key <0 or key > self.getlength():
      print 'the given key is error'
      return
    else:
      return self.getitem(key)
  def __setitem__(self, key, value):
    if self.is_empty():
      print 'linklist is empty.'
      return
    elif key <0 or key > self.getlength():
      print 'the given key is error'
      return
    else:
      self.delete(key)
      return self.insert(key)
  def initlist(self,data):
    self.head = Node(data[0])
    p = self.head
    for i in data[1:]:
      node = Node(i)
      p.next = node
      node.prev = p
      p = p.next
  def getlength(self):
    p = self.head
    length = 0
    while p!=0:
      length+=1
      p = p.next
    return length
  def is_empty(self):
    if self.getlength() ==0:
      return True
    else:
      return False
  def clear(self):
    self.head = 0
  def append(self,item):
    q = Node(item)
    if self.head ==0:
      self.head = q
    else:
      p = self.head
      while p.next!=0:
        p = p.next
      p.next = q
      q.prev = p
  def getitem(self,index):
    if self.is_empty():
      print 'Linklist is empty.'
      return
    j = 0
    p = self.head
    while p.next!=0 and j <index:
      p = p.next
      j+=1
    if j ==index:
      return p.data
    else:
      print 'target is not exist!'
  def insert(self,index,item):
    if self.is_empty() or index<0 or index >self.getlength():
      print 'Linklist is empty.'
      return
    if index ==0:
      q = Node(item,self.head)
      self.head = q
    p = self.head
    post = self.head
    j = 0
    while p.next!=0 and j<index:
      post = p
      p = p.next
      j+=1
    if index ==j:
      q = Node(item,p)
      post.next = q
      q.prev = post
      q.next = p
      p.prev = q
  def delete(self,index):
    if self.is_empty() or index<0 or index >self.getlength():
      print 'Linklist is empty.'
      return
    if index ==0:
      q = Node(item,self.head)
      self.head = q
    p = self.head
    post = self.head
    j = 0
    while p.next!=0 and j<index:
      post = p
      p = p.next
      j+=1
    if index ==j:
      post.next = p.next
      p.next.prev = post
  def index(self,value):
    if self.is_empty():
      print 'Linklist is empty.'
      return
    p = self.head
    i = 0
    while p.next!=0 and not p.data ==value:
      p = p.next
      i+=1
    if p.data == value:
      return i
    else:
      return -1
l = LinkList()
l.initlist([1,2,3,4,5])
print "脚本之家测试结果："
print l.getitem(4)
l.append(6)
print l.getitem(5)
l.insert(4,40)
print l.getitem(3)
print l.getitem(4)
print l.getitem(5)
l.delete(5)
print l.getitem(5)
l.index(5)
结果为；

和单链表结果一样。

PS：双向链表就是将链表首尾相接。