Python数据结构——链表（二）双链表

续之前的单链表

定义节点

class node(object):
    def __init__(self,item):
        self.item = item
        self.next = None
        self.pre = None

item代表存储的内容，next用来模拟指针指向后一个节点，pre用来模拟指针指向前一节点。

插入节点示意图

插入节点1.png

插入节点2.png

创建双链表类

• length：链表长度
• head：链表头节点
• count：现有节点数

class bidirectchainlist(object):
    def __init__(self,length:int):
        self.length = length
        self.head = node(None)
        self.count = 0
        
    def __num_node(self,x:int):
        self.count += x
    
    def search(self,x:node,mode='b'):
        '''
        mode='b':search for the node and return the precvious node, backward
        mode='f':search for the node and return the next node, forward
        '''
        if mode=='b':
            if self.head.next == x:
                return self.head
            else:
                temp = self.head.next
                while temp.next != x:
                    temp = temp.next
                return temp
        elif mode=='f':
            if self.find_tail() == x:
                return x
            elif self.find_tail().pre == x:
                return self.find_tail()
            else:
                temp = self.find_tail().pre
                while temp.pre != x:
                    temp = temp.pre
                return temp
        
    def add_node(self,node:node): # add at the end of chainself.search(x).next
        if self.count == self.length:
            print('cannot exceed max length')
        else:
            temp = self.find_tail()
            self.find_tail().next = node
            node.pre = temp
            self.__num_node(1)
            
    def find_tail(self,x=None): # find the last node
        if x is None:
            x = self.head
        if x.next is None:
            return x
        else:
            temp = x.next
            if temp.next is None:
                return temp
            else:
                return self.find_tail(temp)
    
    def del_node(self,x=None):
        if self.head.next is None:
            print('no node any more!')
        else:
            if x is None:
                self.search(self.find_tail()).next=None
                self.__num_node(-1)
            else:
                temp = self.search(x)
                self.search(x).next = x.next
                x.next.pre = temp
                x = None
                self.__num_node(-1)
    
    def insert_node(self,x:node,y:node):
        if self.count == self.length:
            print('cannot exceed max length')
        else:
            if self.head.next is None:
                self.head.next = y
                y.pre = self.head
                self.__num_node(1)
            else:
                temp = self.search(x)
                temp.next = y
                y.pre = temp
                y.next = x
                x.pre = y
                self.__num_node(1)
            
    def get_chain(self):
        chain = [self.head]
        while chain[-1].next != None:
            chain.append(chain[-1].next)
        return chain

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