python数据结构之单向循环链表

class Node():
    def __init__(self,elem):
        self.elem = elem
        self.next = None
# 是带有头结点的单向循环链表，还是不带头结点的单向循环链表
class SingleXunHuanLinkList():
    # 创建头结点,有默认参数
    def __init__(self,  head=None):
        self.__head = head
        if head:
            head.next = head
    # 判断链表是否为空
    def is_empty(self):
        return self.__head.next == self.__head

    # 返回链表长度
    def length(self):
        p = self.__head.next
        length = 0
        while p!=self.__head:
            length += 1
            p = p.next
        return length
    # 遍历链表
    def travel(self):
        if self.is_empty():
            print("单向循环链表为空")
            return
        p = self.__head.next
        while p!= self.__head:
            print(p.elem,end=" ")
            p = p.next
    # 头插法创建循环单链表
    def add(self,item):
        node = Node(item)
        if self.is_empty():
            self.__head.next = node
            node.next = self.__head
        else:
            p = self.__head
            node.next = p.next
            p.next = node

    # 尾插法创建单向循环链表
    def append(self, item):
        # 根据传进来的数字创建新节点
        node = Node(item)
        if self.__head.next==self.__head:
            self.__head.next = node
            node.next = self.__head
        else:
            p = self.__head
            while p.next!=self.__head:
                p = p.next
            p.next = node
            node.next = self.__head

    # 在某一位置插入节点
    def insert(self,pos,item):
        if pos<0:
            print()
            print("error")
            return
        elif pos>=self.length():
            self.append(item)
        else:
            index = 0
            node = Node(item)
            p = self.__head.next
            while p!=None:
                index = index + 1
                if index==pos:
                    node.next = p.next
                    p.next = node
                p = p.next

    def remove(self,item):
        if self.is_empty():
            print("单链表已经为空，无法删除")
        elif self.length()==1 and item==1:
            self.__head.next = self.__head
        elif item>self.length():
            print("该位置没有节点")
        else:
            p = self.__head
            pos = 0
            while p.next!=self.__head:
                pos = pos+1
                if pos==item:
                    p.next = p.next.next
                p = p.next

    # 查找指定位置的节点
    def search(self,item):
        if item<=0 and item>self.length():
            print("该位置越界")
            return
        else:
            p = self.__head.next
            pos = 0
            while p!=self.__head:
                pos +=1
                if pos==item:
                    return p.elem
                p = p.next
if __name__=='__main__':
    # 创建一个节点
    head = Node(0)
    xunhuan = SingleXunHuanLinkList(head)
    print(xunhuan.is_empty())
    print(xunhuan.length())
    xunhuan.travel()
    xunhuan.append(4)
    xunhuan.append(5)
    xunhuan.append(6)
    xunhuan.travel()
    print()
    xunhuan.add(1)
    xunhuan.add(2)
    xunhuan.add(3)
    xunhuan.travel()
    print()
    print(xunhuan.is_empty())
    print(xunhuan.length())
    xunhuan.insert(9,10)
    xunhuan.travel()
    print()
    print("删除节点")
    xunhuan.remove(6)
    xunhuan.travel()
    print()
    print("查询节点")
    print(xunhuan.search(4))