单向循环链表

　　单向循环链表，相对于单向链表来说区别就是尾节点不再是指向None，而是指向头节点。

代码实现

# -*- coding = utf-8 -*-
# @Author: Wchime
# @time: 2023/1/20 15:31
# @file: 单向循环链表.py


class Node(object):
    """单向链表节点"""
    def __init__(self, item):
        self.item = item
        self.next = None


class SingleLoopList(object):
    """
    单向循环链表
    """
    def __init__(self, node=None):
        self.__link = node
        if node:
            node.next = node

    def is_empty(self):
        """
        判断链表是否为空
        :return:
        """
        return self.__link is None

    def get_length(self):
        """
        获取链表长度
        循环链表最后节点next不是None值，而是第一个节点
        :return:
        """
        if self.is_empty():
            return 0
        else:
            cur = self.__link
            count = 1
            while cur.next != self.__link:
                count += 1
                cur = cur.next
            return count

    def append(self, item):
        """
        添加节点, 当链表不是空链表时，需要找到最后一个节点, 最后节点的判断的等于第一个节点
        :param item:
        :return:
        """
        node = Node(item)
        if self.is_empty():
            self.__link = node
            node.next = node
        else:
            cur = self.__link
            while cur.next != self.__link:
                cur = cur.next
            cur.next = node
            node.next = self.__link

    def insert(self, index, item):
        """
        在指定位置插入节点
        :param index:
        :param item:
        :return:
        """
        # print(self.get_length())
        if index == 0:
            node = Node(item)
            if self.is_empty():
                self.__link = node
                node.next = node
                return
            cur = self.__link
            while cur.next != self.__link:
                cur = cur.next
            node.next = self.__link
            self.__link = node
            cur.next = node
        elif index > self.get_length()-1:
            self.append(item)

        else:
            pre = self.__link
            count = 0
            while count < index - 1:
                count += 1
                pre = pre.next
            node = Node(item)
            node.next = pre.next
            pre.next = node

    def remove(self, item):
        """
        根据值删除节点
        :param item:
        :return:
        """
        if self.is_empty():
            return
        cur = self.__link
        pre = None
        while cur.next != self.__link:
            if cur.item == item:
                if cur == self.__link:
                    # 头节点
                    rear = self.__link
                    while rear.next != self.__link:
                        rear = rear.next
                    self.__link = cur.next
                    rear.next = self.__link
                else:
                    # 中间节点
                    pre.next = cur.next
                return
            else:
                pre = cur
                cur = cur.next
        # 尾节点
        if cur.item == item:
            if cur == self.__link:
                self.__link = None
            else:
                pre.next = cur.next

    def search(self,item):
        """
        查找节点是否存在
        :param item:
        :return:
        """
        if self.is_empty():
            return False
        cur = self.__link
        while cur.next != self.__link:
            if cur.item == item:
                return True
            else:
                cur = cur.next
        if cur.item == item:
            return True
        return False

    def travel(self):
        """
        链表遍历
        :return:
        """
        if self.is_empty():
            return
        cur = self.__link
        while cur.next != self.__link:
            print(cur.item,end="  ")
            cur = cur.next
        print(cur.item)


if __name__ == "__main__":

    singlelist = SingleLoopList()
    singlelist.append(1)
    singlelist.append(7)
    singlelist.append(5)
    singlelist.travel()

    singlelist.insert(1, 66)
    singlelist.travel()

    length = singlelist.get_length()
    print(length)

    print(singlelist.search(66))

    singlelist.remove(66)
    singlelist.travel()

    print(singlelist.is_empty())