1.什么是无序表?

一种数据项按照相对位置存放的数据集，特别的，被称为“无序集unordered list”，其中数据项只按照存放位置来索引，如第一个、第二个等等。

2.无序表的定义

List():创建一个空列表
add(item):添加一个数据项到列表中,假设item原来不存在于列表中
remove(item):从列表中移除item,列表被修改,item原先存在应存在表中
search:在列表中查找item,返回布尔类型值
is_Empty:返回列表是否为空
size:返回列表包含了多少数据项
append(item):添加一个数据项到表末尾,假设item原先不存在列表中
index(item):返回数据项在表中的位置
insert(pos,item):将数据项插入到位置pos,假设item原先不存在与列表中,同时原列表具有足够多个数据项,能让item占据位置pos
pos():从列表末尾移除数据项,假设原列表至少有1个数据项
pop(pos):移除位置为pos的数据项,假设原列表存在位置pos

3.Python用链表实现无序表

# 链表实现:节点Node
class Node:
	def __init__(self,initdata):
		self.data = initdata
		self.next = None
	
	def getData(self):
		return self.data
	
	def getNext(self):
		return self.next
	
	def setData(self,newdata):
		self.data = newdata
	
	def setNext(self,newnext):
		self.next = newnext

# 链表实现: 无序表UnorderndList
class UnorderndList:
	def __init__(self):
		self.head = None
	
	def is_Empty(self):
	"""判断链表是否为空"""
		return self.head == None
	
	def add(self,item):
	"""添加数据"""
		temp = Node(item)
		temp.setNext(self.head)
		self.head = temp
	
	def size(self):
	"""返回数据项的个数"""
		current = self.head
		count = 0
		while != None:
			count = count + 1
			current = current.getNext()
		return count
	
	def search(self,item):
	"""搜索数据项"""
		current = self.head
		found = False
		while current != None and not found:
			if current.getData() == item:
				found = True
			else:
				current = current.getNext()
		return found
	
	def remove(self,item):
	"""删除数据项"""
		current = self.head
		previous = None
		found = False
		while not found:
			if current.getData() == item:
				found = True
			else:
				previous = current
				current = current.getNext()
		
		if previous == None:
			self.head = current.getNext()
		else:
			previous.setNext(current.getNext())
	
	def append(self,item):
	"""在链表尾部插入item"""
		node = Node(item)
		current = self.head
		if current is None:
			self.head = node
		while current.getNext() is not None:
			current = current.getNext()
		current.setNext(node)
	
	 
    def index(self, item):
    """查询元素item"""
        current = self.head
        count = 0
        while current != None:
            if current.getData() == item:
                return count
            current = current.getNext()
            count += 1
        return -1

    def pop(self, index=None):
    """删除尾部元素"""
        previous = None
        current = self.head
        if index == None: #默认删除尾部的元素并返回
            index = self.size() - 1
        if index < 0 or index >= (self.size()): #index不能小于0 或者 超出链表的大小
            raise IndexError
        while self.index(current.getData()) != index: #判断当前节点对应的索引是否等于index
            previous = current
            current = current.getNext()
        data = current.getData()
        #和remove方法类似
        if previous == None: 	
            self.head = current.getNext()
        else:
            previous.setNext(current.getNext())
        return data

    
    def insert(self, index, item):
    """在item插入元素"""
        node = Node(item)
        if index == 0:
            node.setNext(self.head)
            self.head = node
        else:
            if index < 0 or (index >= self.size()):
                raise IndexError
            current = self.head
            previous = None
            while self.index(current.getData()) != index:
                previous = current
                current = current.getNext()
                if current is None:
                    break
            previous.setNext(node)
            node.setNext(current)

    def reverseList(self):
    """链表反向排序"""
        previous = None
        temp = None
        current = self.head
        while current != None:
            temp = current.getNext()
            current.setNext(previous)
            previous = current #将current 和previou 节点向链表的前方移动
            current = temp
            if previous != self.head:
                self.add(previous.getData())
        return self