Python數據結構——鏈表的實現

鏈表由一系列沒必要在內存中相連的結構構成,這些對象按線性順序排序。每一個結構含有表元素和指向後繼元素的指針。最後一個單元的指針指向NULL。爲了方便鏈表的刪除與插入操做,能夠爲鏈表添加一個表頭。前端

 

 刪除操做能夠經過修改一個指針來實現。python

插入操做須要執行兩次指針調整。app

 

1. 單向鏈表的實現

1.1 Node實現指針

    每一個Node分爲兩部分。一部分含有鏈表的元素,能夠稱爲數據域;另外一部分爲一指針,指向下一個Node。對象

class Node():
    __slots__=['_item','_next']    #限定Node實例的屬性
    def __init__(self,item):
        self._item=item
        self._next=None     #Node的指針部分默認指向None
    def getItem(self):
        return self._item
    def getNext(self):
        return self._next
    def setItem(self,newitem):
        self._item=newitem
    def setNext(self,newnext):
        self._next=newnext

1.2 SinglelinkedList的實現blog

class SingleLinkedList():   
    def __init__(self):
        self._head=None    #初始化鏈表爲空表
        self._size=0

1.3 檢測鏈表是否爲空排序

def isEmpty(self):
    return self._head==None   

1.4 add在鏈表前端添加元素索引

def add(self,item):
    temp=Node(item)
    temp.setNext(self._head)
    self._head=temp

1.5 append在鏈表尾部添加元素內存

def append(self,item):
    temp=Node(item)
    if self.isEmpty():
        self._head=temp   #若爲空表,將添加的元素設爲第一個元素
    else:
        current=self._head
        while current.getNext()!=None:
            current=current.getNext()   #遍歷鏈表
        current.setNext(temp)   #此時current爲鏈表最後的元素
    

1.6 search檢索元素是否在鏈表中rem

def search(self,item):
    current=self._head
    founditem=False
    while current!=None and not founditem:
        if current.getItem()==item:
            founditem=True
        else:
            current=current.getNext()
    return founditem

1.7 index索引元素在鏈表中的位置

def index(self,item):
    current=self._head
    count=0
    found=None
    while current!=None and not found:
        count+=1
        if current.getItem()==item:
            found=True
        else:
            current=current.getNext()
    if found:
        return count
    else:
        raise ValueError,'%s is not in linkedlist'%item  

1.8 remove刪除鏈表中的某項元素

def remove(self,item):
    current=self._head
    pre=None
    while current!=None:
        if current.getItem()==item:
            if not pre:
                self._head=current.getNext()
            else:
                pre.setNext(current.getNext())
            break
        else:
            pre=current
            current=current.getNext()

1.9 insert鏈表中插入元素

 def insert(self,pos,item):
    if pos<=1:
        self.add(item)
    elif pos>self.size():
        self.append(item)
    else:
        temp=Node(item)
        count=1
        pre=None
        current=self._head
        while count<pos:
            count+=1
            pre=current
            current=current.getNext()
        pre.setNext(temp)
        temp.setNext(current)

所有代碼

class Node():
    __slots__=['_item','_next']
    def __init__(self,item):
        self._item=item
        self._next=None
    def getItem(self):
        return self._item
    def getNext(self):
        return self._next
    def setItem(self,newitem):
        self._item=newitem
    def setNext(self,newnext):
        self._next=newnext
        
class SingleLinkedList():   
    def __init__(self):
        self._head=None  #初始化爲空鏈表
    def isEmpty(self):
        return self._head==None
    def size(self):
        current=self._head
        count=0
        while current!=None:
            count+=1
            current=current.getNext()
        return count
    def travel(self):
        current=self._head
        while current!=None:
            print current.getItem()
            current=current.getNext()
    def add(self,item):
        temp=Node(item)
        temp.setNext(self._head)
        self._head=temp

    def append(self,item):
        temp=Node(item)
        if self.isEmpty():
            self._head=temp   #若爲空表,將添加的元素設爲第一個元素
        else:
            current=self._head
            while current.getNext()!=None:
                current=current.getNext()   #遍歷鏈表
            current.setNext(temp)   #此時current爲鏈表最後的元素
    def search(self,item):
        current=self._head
        founditem=False
        while current!=None and not founditem:
            if current.getItem()==item:
                founditem=True
            else:
                current=current.getNext()
        return founditem
    def index(self,item):
        current=self._head
        count=0
        found=None
        while current!=None and not found:
            count+=1
            if current.getItem()==item:
                found=True
            else:
                current=current.getNext()
        if found:
            return count
        else:
            raise ValueError,'%s is not in linkedlist'%item                
    def remove(self,item):
        current=self._head
        pre=None
        while current!=None:
            if current.getItem()==item:
                if not pre:
                    self._head=current.getNext()
                else:
                    pre.setNext(current.getNext())
                break
            else:
                pre=current
                current=current.getNext()                        
    def insert(self,pos,item):
        if pos<=1:
            self.add(item)
        elif pos>self.size():
            self.append(item)
        else:
            temp=Node(item)
            count=1
            pre=None
            current=self._head
            while count<pos:
                count+=1
                pre=current
                current=current.getNext()
            pre.setNext(temp)
            temp.setNext(current)

if __name__=='__main__':
    a=SingleLinkedList()
    for i in range(1,10):
        a.append(i)
    print a.size()
    a.travel()
    print a.search(6)
    print a.index(5)
    a.remove(4)
    a.travel()
    a.insert(4,100)
    a.travel()
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