Python数据结构——链表的实现

链表由一系列不必在内存中相连的结构构成，这些对象按线性顺序排序。每个结构含有表元素和指向后继元素的指针。最后一个单元的指针指向NULL。为了方便链表的删除与插入操作，可以为链表添加一个表头。

 

 删除操作可以通过修改一个指针来实现。

插入操作需要执行两次指针调整。

 

1. 单向链表的实现

1.1 Node实现

    每个Node分为两部分。一部分含有链表的元素，可以称为数据域；另一部分为一指针，指向下一个Node。

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class Node():     __slots__=['_item','_next']    #限定Node实例的属性     def __init__(self,item):         self._item=item         self._next=None     #Node的指针部分默认指向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的实现

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class SingleLinkedList():       def __init__(self):         self._head=None    #初始化链表为空表         self._size=0

1.3 检测链表是否为空

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1 2	def isEmpty(self):     return self._head==None

1.4 add在链表前端添加元素

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

1.5 append在链表尾部添加元素

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def append(self,item):     temp=Node(item)     if self.isEmpty():         self._head=temp   #若为空表，将添加的元素设为第一个元素     else:         current=self._head         while current.getNext()!=None:             current=current.getNext()   #遍历链表         current.setNext(temp)   #此时current为链表最后的元素

1.6 search检索元素是否在链表中

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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索引元素在链表中的位置

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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删除链表中的某项元素

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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链表中插入元素

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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)

全部代码

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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  #初始化为空链表     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   #若为空表，将添加的元素设为第一个元素         else:             current=self._head             while current.getNext()!=None:                 current=current.getNext()   #遍历链表             current.setNext(temp)   #此时current为链表最后的元素     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()