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。
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()