Python 数据结构与算法——链表

#构造节点类
class Node(object):
    def __init__(self,data=None,_next=None):
        '''
        self.data:为自定义的数据
        self.next:下一个节点的地址（这里为下一个数据建立了一个对象）
        '''
        self.data = data
        self.next = _next
        
    def __repr__(self):
        return str(self.data)
    
#单链表
class MyChain(object):
    def __init__(self):
       '''初始化空链表'''
        self.head=None
        self.length=0
        
    def __repr__(self):
        """ 重构：对链表进行输出 """
        temp = self.head
        cstr = ""
        for i in range(self.length-1):
            cstr += str(temp.data)+' -> '
            temp = temp.next
        cstr += str(temp.data)
        return cstr
    
    def isEmpty(self):
        return (self.length==0)
    
    def append(self, mydata):
        '''增加节点'''
        item=None
        if isinstance(mydata, Node):
            item=mydata
        else:
            item=Node(mydata)
            
        if not self.head:
            self.head=item
            self.length +=1
        else:
            node=self.head
            while node.next:
                node=node.next
            node.next=item
            self.length += 1
        
    def delete(self,index):
        if self.isEmpty():
            print("this chain table is empty")
            return 
        
        if index<0 or self.length<=index:
            print("index is out of range")
            return
        if index==0:
            self.head=self.head.next
            self.length -=1
            return
        #prev为保存前导节点
        #node为保存当前节点
        #当j与index相等时就
        #相当于找到要删除的节点
        j=0
        node=self.head
        prev=self.head
        while node.next and j < index:
            prev = node
            node = node.next
            j += 1

        if j == index:
            prev.next = node.next
            self.length -= 1
        
    def update(self, index, data):
        '''修改节点'''
        if self.isEmpty() or index < 0 or index >= self.length:
            print('error: out of index')
            return
        j = 0
        node = self.head
        while node.next and j < index:
            node = node.next
            j += 1
    
        if j == index:
            node.data = data
            
    def getItem(self, index):
        '''查找节点'''
        if self.isEmpty() or index < 0 or index >= self.length:
            print("error: out of index")
            return
        j = 0
        node = self.head
        while node.next and j < index:
            node = node.next
            j += 1
    
        return node.data
    
    def getIndex(self, data):
        j = 0
        if self.isEmpty():
            print("this chain table is empty")
            return
        node = self.head
        while node:
            if node.data == data:
                print("index is %s"%str(j))
                return j
            node = node.next
            j += 1
    
        if j == self.length:
            print ("%s not found" % str(data))
            return
        
    def insert(self, index, mydata):
        if self.isEmpty():
            print ("this chain tabale is empty")
            return
    
        if index < 0 or index >= self.length:
            print ("error: out of index")
            return
    
        item = None
        if isinstance(mydata, Node):
            item = mydata
        else:
            item = Node(mydata)
    
        if index == 0:
            item.next = self.head
            self.head = item
            self.length += 1
            return
    
        j = 0
        node = self.head
        prev = self.head
        while node.next and j < index:
            prev = node
            node = node.next
            j += 1
    
        if j == index:
            item.next = node
            prev.next = item
            self.length += 1
            
    def clear(self):
        self.head = None
        self.length = 0
        
if __name__=="__main__":
    L = [1,2,3,4,5,6,7,8,9,0]
    chain = MyChain()
    for i in L:
        n = Node(i)
        chain.append(n)
    chain.getIndex(2) 
    chain.insert(0, 0) 
    chain.getItem(9)
    chain.update(3, 77)
    print(chain)