python实现循环双端链表

# -*- coding:utf-8 -*-
"""
每一个结点包含prev， value ， next。 prev指向上一个结点。 root根节点作为接口。根节点的下一个结点是head结点。尾结点尾tail，tail.next=root, root.prev = tail所以说这是一个双端循环结点
"""



class Node(object):
    def __init__(self, prev = None, value = None, next = None):
        self.value = value
        self.next = next
        self.prev = prev


class CircualDoubleLinedList(object):

    def __init__(self, maxsize=None):
        self.maxsize = maxsize
        node = Node()
        node.next, node.prev = node, node
        self.root = node            # 根结点默认是自己指向自己的
        self.length = 0


    def __len__(self):
        return self.length


    def headnode(self):         # 获取头结点
        return self.root.next


    def tailnode(self):         # 获取尾结点
        return self.root.prev


    def append(self, value):       # 加入到尾结点的后面。 该结点的下一结点是root， 上一结点是尾结点tailnode
        if self.maxsize is not None and len(self) > self.maxsize:
            raise Exception('full')
        node = Node(value = value)
        tailnode = self.tailnode()   # 获取尾结点
        tailnode.next = node
        node.prev = tailnode
        node.next = self.root
        self.root.prev = node

        self.length += 1


    def appendleft(self, value):
        if self.maxsize is not None and len(self) > self.maxsize:
            raise Exception('full')
        node = Node(value = value)

        if self.root.next  is self.root:     # 此时双端链表为空 除了根结点外只有一个结点
            self.root.next = node
            self.root.prev = node
            node.next = self.root
            node.prev = self.root
        else:
            head = self.root.next
            self.root.next = node
            node.prev = self.root
            node.next = head
            head.prev = node

        self.length += 1



    def remove(self, node):       # 这里传入的node， 不是value
        if node is self.root:
            return
        else:
            node.prev.next = node.next
            node.next.prev = node.prev

        self.length -= 1
        return node


    def iter_node(self):     #  遍历结点
        if self.root.next is self.root: # 此时链表为空 不做任何事情
            return
        curnode = self.root.next
        while curnode.next is not self.root:
            yield curnode
            curnode = curnode.next
        yield curnode    # yield 尾结点


    def __iter__(self):
        for node in self.iter_node():
            yield node.value


    def iter_node_reverse(self): # 反向遍历
        if self.root.prev is self.root:
            return

        curnode = self.root.prev    # tailnode
        while curnode.prev is not self.root:
            yield curnode
            curnode =  curnode.prev
        yield curnode


    def insert(self, value, new_value):     #   插入替换方法
        for node in self.iter_node():
            if node.value == value:
                node.value = new_value


def test_double_link_lis():  　　　　　　
    dll = CircualDoubleLinedList()
    assert len(dll) == 0
    dll.append(0)
    dll.append(1)
    dll.append(2)
    assert len(dll) == 3
    assert list(dll) == [0, 1, 2]     # 会调用iter方法

    assert [node.value for node in dll.iter_node()] == [0,1,2]
    assert [node.value for node in dll.iter_node_reverse()] == [2,1,0]



    headnode = dll.headnode()
    assert headnode.value == 0
    dll.remove(headnode)
    assert len(dll) == 2
    assert [node.value for node in dll.iter_node()] == [1,2]

    dll.appendleft(0)
    assert len(dll) == 3
    assert [node.value for node in dll.iter_node()] == [0,1,2]


    dll.insert(0,3)
    assert [node.value for node in dll.iter_node()] == [3,1,2]