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。
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
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
def isEmpty(self): return self._head==None
1.4 add在链表前端添加元素
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
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
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
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
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
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
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()
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