Python写数据结构:双向循环链表

注：有头结点

#!/usr/bin/python3.5
# _*_coding:utf-8

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


class CycleDoubleLinkList:
    def __init__(self):
        self._head = Node(None)
        self._head.next = self._head
        self._head.prev = self._head
        self._rear = self._head

    def insert(self, index, value):
        if index <= 0:
            print('插入位置有误')
            return
        n = Node(value)
        cur = self._head
        for i in range(index - 1):
            cur = cur.next
            if cur == self._head:
                print('插入位置有误')
                return
        n.next = cur.next
        cur.next.prev = n
        cur.next = n
        n.prev = cur
        if n.next == self._head:
            self._rear = n

    def remove(self, index):
        if self.empty():
            print('链表是空的')
        if index <= 0 and index > self.length():
            print('删除位置有误')
            return
        cur = self._head
        for i in range(index - 1):
            cur = cur.next
        n = cur.next
        cur.next.next.prev = cur
        cur.next = cur.next.next
        if cur.next == self._head:
            self._rear = cur
        del n

    def empty(self):
        return self._head.next == self._head

    def travel(self):
        cur = self._head.next
        print('正向输出:')
        while cur != self._head:
            print(cur.data)
            cur = cur.next
        print('逆向输出:')
        while cur.prev != self._head:
            cur = cur.prev
            print(cur.data)

    def search(self,value):
        cur = self._head.next
        index = 1
        while cur != self._head:
            if cur.data == value:
                print('index:%d,value:%d' % (index,value))
                return
            cur = cur.next
            index += 1
        print('没有该元素')

    def clear(self):
        cur = self._head.next
        while cur != self._head:
            temp = cur
            cur = cur.next
            del temp
        self._head.next = self._head
        self._head.prev = self._head

    def appendleft(self,value):
        n = Node(value)
        self._head.next.prev = n
        n.next = self._head.next
        self._head.next = n
        n.prev = self._head
        if n.next == self._head:
            self._rear = n

    def appendright(self,value):
        n = Node(value)
        self._rear.next.prev = n
        n.next = self._rear.next
        self._rear.next = n
        n.prev = self._rear
        self._rear = n

    def length(self):
        cur = self._head.next
        count = 0
        while cur != self._head:
            cur = cur.next
            count += 1
        return count


if __name__ == '__main__':
    link = CycleDoubleLinkList()