Detailed explanation of the code to implement linked list in Python-Python Tutorial-php.cn

This article mainly introduces the relevant information about the example code of Python to implement the linked list. Friends who need it can refer to

The example code of Python to implement the linked list

Foreword

Algorithms and data structures are an everlasting topic. As a programmer, it is very, very necessary to master the implementation of commonly used data structures.

Implementation List

Implementing a linked list is essentially independent of language. But flexibility is closely related to the language used to implement it. Today I will use Python to implement it, including the following operations:

[&#39;addNode(self, data)&#39;]
[&#39;append(self, value)&#39;]
[&#39;prepend(self, value)&#39;]
[&#39;insert(self, index, value)&#39;]
[&#39;delNode(self, index)&#39;]
[&#39;delValue(self, value)&#39;]
[&#39;isempty(self)&#39;]
[&#39;truncate(self)&#39;]
[&#39;getvalue(self, index)&#39;]
[&#39;peek(self)&#39;]
[&#39;pop(self)&#39;]
[&#39;reverse(self)&#39;]
[&#39;delDuplecate(self)&#39;]
[&#39;updateNode(self, index, value)&#39;]
[&#39;size(self)&#39;]
[&#39;print(self)&#39;]

Copy after login

Generating such a method list must not be written manually, otherwise it will be very troublesome, so I wrote a program to match these and implement it myself Methods. The code is relatively simple. The core idea is to match each line of the source file, find content that meets the matching rules, and add it to the total result set.

The code is as follows:

# coding: utf8

# @Author: 郭 璞
# @File: getmethods.py                                 
# @Time: 2017/4/5                  
# @Contact: 1064319632@qq.com
# @blog: http://blog.csdn.net/marksinoberg
# @Description: 获取一个模块或者类中的所有方法及参数列表

import re

def parse(filepath, repattern):
  with open(filepath, &#39;rb&#39;) as f:
    lines = f.readlines()
  # 预解析正则
  rep = re.compile(repattern)
  # 创建保存方法和参数列表的结果集列表
  result = []
  # 开始正式的匹配实现
  for line in lines:
    res = re.findall(rep, str(line))
    print("{}的匹配结果{}".format(str(line), res))
    if len(res)!=0 or res is not None:
      result.append(res)
    else:
      continue
  return [item for item in result if item !=[]]


if __name__ == &#39;__main__&#39;:
  repattern = "def (.[^_0-9]+\(.*?\)):"
  filepath = &#39;./SingleChain.py&#39;
  result = parse(filepath, repattern)
  for item in result:
    print(str(item))

Copy after login

Linked list implementation

# coding: utf8

# @Author: 郭 璞
# @File: SingleChain.py                                 
# @Time: 2017/4/5                  
# @Contact: 1064319632@qq.com
# @blog: http://blog.csdn.net/marksinoberg
# @Description: 单链表实现

class Node(object):
  def __init__(self, data, next):
    self.data = data
    self.next = next

class LianBiao(object):

  def __init__(self):
    self.root = None

  # 给单链表添加元素节点
  def addNode(self, data):
    if self.root==None:
      self.root = Node(data=data, next=None)
      return self.root
    else:
      # 有头结点，则需要遍历到尾部节点，进行链表增加操作
      cursor = self.root
      while cursor.next!= None:
        cursor = cursor.next
      cursor.next = Node(data=data, next=None)
      return self.root

  # 在链表的尾部添加新节点，底层调用addNode方法即可
  def append(self, value):
    self.addNode(data=value)

  # 在链表首部添加节点
  def prepend(self, value):
    if self.root == None:
      self.root = Node(value, None)
    else:
      newroot = Node(value, None)
      # 更新root索引
      newroot.next = self.root
      self.root = newroot

  # 在链表的指定位置添加节点
  def insert(self, index, value):
    if self.root == None:
      return
    if index<=0 or index >self.size():
      print(&#39;index %d 非法， 应该审视一下您的插入节点在整个链表的位置！&#39;)
      return
    elif index==1:
      # 如果index==1， 则在链表首部添加即可
      self.prepend(value)
    elif index == self.size()+1:
      # 如果index正好比当前链表长度大一，则添加在尾部即可
      self.append(value)
    else:
      # 如此，在链表中部添加新节点，直接进行添加即可。需要使用计数器来维护插入未知
      counter = 2
      pre = self.root
      cursor = self.root.next
      while cursor!=None:
        if counter == index:
          temp = Node(value, None)
          pre.next = temp
          temp.next = cursor
          break
        else:
          counter += 1
          pre = cursor
          cursor = cursor.next

  # 删除指定位置上的节点
  def delNode(self, index):
    if self.root == None:
      return
    if index<=0 or index > self.size():
      return
    # 对第一个位置需要小心处理
    if index == 1:
      self.root = self.root.next
    else:
      pre = self.root
      cursor = pre.next
      counter = 2
      while cursor!= None:
        if index == counter:
          print(&#39;can be here!&#39;)
          pre.next = cursor.next
          break
        else:
          pre = cursor
          cursor = cursor.next
          counter += 1

  # 删除值为value的链表节点元素
  def delValue(self, value):
    if self.root == None:
      return
    # 对第一个位置需要小心处理
    if self.root.data == value:
      self.root = self.root.next
    else:
      pre = self.root
      cursor = pre.next
      while cursor!=None:
        if cursor.data == value:
          pre.next = cursor.next
          # 千万记得更新这个节点，否则会出现死循环。。。
          cursor = cursor.next
          continue
        else:
          pre = cursor
          cursor = cursor.next

  # 判断链表是否为空
  def isempty(self):
    if self.root == None or self.size()==0:
      return True
    else:
      return False

  # 删除链表及其内部所有元素
  def truncate(self):
    if self.root == None or self.size()==0:
      return
    else:
      cursor = self.root
      while cursor!= None:
        cursor.data = None
        cursor = cursor.next
      self.root = None
      cursor = None

  # 获取指定位置的节点的值
  def getvalue(self, index):
    if self.root is None or self.size()==0:
      print(&#39;当前链表为空！&#39;)
      return None
    if index<=0 or index>self.size():
      print("index %d不合法！"%index)
      return None
    else:
      counter = 1
      cursor = self.root
      while cursor is not None:
        if index == counter:
          return cursor.data
        else:
          counter += 1
          cursor = cursor.next

  # 获取链表尾部的值，且不删除该尾部节点
  def peek(self):
    return self.getvalue(self.size())

  # 获取链表尾部节点的值，并删除该尾部节点
  def pop(self):
    if self.root is None or self.size()==0:
      print(&#39;当前链表已经为空！&#39;)
      return None
    elif self.size()==1:
      top = self.root.data
      self.root = None
      return top
    else:
      pre = self.root
      cursor = pre.next
      while cursor.next is not None:
        pre = cursor
        cursor = cursor.next
      top = cursor.data
      cursor = None
      pre.next = None
      return top

  # 单链表逆序实现
  def reverse(self):
    if self.root is None:
      return
    if self.size()==1:
      return
    else:
      # post = None
      pre = None
      cursor = self.root
      while cursor is not None:
        # print(&#39;逆序操作逆序操作&#39;)
        post = cursor.next
        cursor.next = pre
        pre = cursor
        cursor = post
      # 千万不要忘记了把逆序后的头结点赋值给root，否则无法正确显示
      self.root = pre

  # 删除链表中的重复元素
  def delDuplecate(self):
    # 使用一个map来存放即可，类似于变形的“桶排序”
    dic = {}
    if self.root == None:
      return
    if self.size() == 1:
      return
    pre = self.root
    cursor = pre.next
    dic = {}
    # 为字典赋值
    temp = self.root
    while temp!=None:
      dic[str(temp.data)] = 0
      temp = temp.next
    temp = None
    # 开始实施删除重复元素的操作
    while cursor!=None:
      if dic[str(cursor.data)] == 1:
        pre.next = cursor.next
        cursor = cursor.next
      else:
        dic[str(cursor.data)] += 1
        pre = cursor
        cursor = cursor.next


  # 修改指定位置节点的值
  def updateNode(self, index, value):
    if self.root == None:
      return
    if index<0 or index>self.size():
      return
    if index == 1:
      self.root.data = value
      return
    else:
      cursor = self.root.next
      counter = 2
      while cursor!=None:
        if counter == index:
          cursor.data = value
          break
        cursor = cursor.next
        counter += 1


  # 获取单链表的大小
  def size(self):
    counter = 0
    if self.root == None:
      return counter
    else:
      cursor = self.root
      while cursor!=None:
        counter +=1
        cursor = cursor.next
      return counter


  # 打印链表自身元素
  def print(self):
    if(self.root==None):
      return
    else:
      cursor = self.root
      while cursor!=None:
        print(cursor.data, end=&#39;\t&#39;)
        cursor = cursor.next
      print()

if __name__ == &#39;__main__&#39;:
  # 创建一个链表对象
  lianbiao = LianBiao()
  # 判断当前链表是否为空
  print("链表为空%d"%lianbiao.isempty())
  # 判断当前链表是否为空
  lianbiao.addNode(1)
  print("链表为空%d"%lianbiao.isempty())
  # 添加一些节点，方便操作
  lianbiao.addNode(2)
  lianbiao.addNode(3)
  lianbiao.addNode(4)
  lianbiao.addNode(6)
  lianbiao.addNode(5)
  lianbiao.addNode(6)
  lianbiao.addNode(7)
  lianbiao.addNode(3)
  # 打印当前链表所有值
  print(&#39;打印当前链表所有值&#39;)
  lianbiao.print()
  # 测试对链表求size的操作
  print("链表的size: "+str(lianbiao.size()))
  # 测试指定位置节点值的获取
  print(&#39;测试指定位置节点值的获取&#39;)
  print(lianbiao.getvalue(1))
  print(lianbiao.getvalue(lianbiao.size()))
  print(lianbiao.getvalue(7))
  # 测试删除链表中指定值， 可重复性删除
  print(&#39;测试删除链表中指定值， 可重复性删除&#39;)
  lianbiao.delNode(4)
  lianbiao.print()
  lianbiao.delValue(3)
  lianbiao.print()
  # 去除链表中的重复元素
  print(&#39;去除链表中的重复元素&#39;)
  lianbiao.delDuplecate()
  lianbiao.print()
  # 指定位置的链表元素的更新测试
  print(&#39;指定位置的链表元素的更新测试&#39;)
  lianbiao.updateNode(6, 99)
  lianbiao.print()
  # 测试在链表首部添加节点
  print(&#39;测试在链表首部添加节点&#39;)
  lianbiao.prepend(77)
  lianbiao.prepend(108)
  lianbiao.print()
  # 测试在链表尾部添加节点
  print(&#39;测试在链表尾部添加节点&#39;)
  lianbiao.append(99)
  lianbiao.append(100)
  lianbiao.print()
  # 测试指定下标的插入操作
  print(&#39;测试指定下标的插入操作&#39;)
  lianbiao.insert(1, 10010)
  lianbiao.insert(3, 333)
  lianbiao.insert(lianbiao.size(), 99999)
  lianbiao.print()
  # 测试peek 操作
  print(&#39;测试peek 操作&#39;)
  print(lianbiao.peek())
  lianbiao.print()
  # 测试pop 操作
  print(&#39;测试pop 操作&#39;)
  print(lianbiao.pop())
  lianbiao.print()
  # 测试单链表的逆序输出
  print(&#39;测试单链表的逆序输出&#39;)
  lianbiao.reverse()
  lianbiao.print()
  # 测试链表的truncate操作
  print(&#39;测试链表的truncate操作&#39;)
  lianbiao.truncate()
  lianbiao.print()

Copy after login

What is the result of running the code? Whether it can meet our needs, let's look at the printed results:

D:\Software\Python3\python.exe E:/Code/Python/Python3/CommonTest/datastructor/SingleChain.py
链表为空1
链表为空0
打印当前链表所有值
1  2  3  4  6  5  6  7  3  
链表的size: 9
测试指定位置节点值的获取
1
3
6
测试删除链表中指定值， 可重复性删除
can be here!
1  2  3  6  5  6  7  3  
1  2  6  5  6  7  
去除链表中的重复元素
1  2  6  5  7  
指定位置的链表元素的更新测试
1  2  6  5  7  
测试在链表首部添加节点
108 77 1  2  6  5  7  
测试在链表尾部添加节点
108 77 1  2  6  5  7  99 100 
测试指定下标的插入操作
10010  108 333 77 1  2  6  5  7  99 99999  100 
测试peek 操作
100
10010  108 333 77 1  2  6  5  7  99 99999  100 
测试pop 操作
100
10010  108 333 77 1  2  6  5  7  99 99999  
测试单链表的逆序输出
99999  99 7  5  6  2  1  77 333 108 10010  
测试链表的truncate操作

Process finished with exit code 0

Copy after login

just meets the target requirements.

Summary

Today’s content is relatively basic and there is nothing difficult about it. But understanding and being able to write are two different things. Writing such code when you have nothing to do is still very rewarding.

The above is the detailed content of Detailed explanation of the code to implement linked list in Python. For more information, please follow other related articles on the PHP Chinese website!