class Node:
    def __init__(self, next, val=None):
        self.val = val  # 值
        self.next = next  # 游标。最后一个元素的游标必须是 0


class SLinkList:
    # 分配线性表长度、定义线性表
    def __init__(self, size=7):
        self.size = size
        self.link = [Node((i + 1) % self.size) for i in range(self.size)]

    # 线性表清空
    def clearSLL(self):
        self.__init__()

    # 线性表是否为空
    def isEmpty(self):
        return False if self.link[self.size - 1].next else True

        # 查找空位置

    def findEmpty(self):
        ind = self.size
        for i in range(1, self.size - 1):
            if self.link[i].val is None:
                ind = i
                break
        return ind

    # 指定位置插入元素
    def insert(self, ind, ele):
        sua = -1
        # 前一个元素
        pre = self.size - 1
        # 插入元素的位置（第一个空位置）
        insertLoc = self.link[0].next
        # 条件判断
        if ind  1 or ind >= pre or insertLoc >= self.size:
            return 0
        # 第一个元素的索引
        for i in range(1, self.size - 1):
            index = self.link[pre].next
            if i == ind:
                self.link[pre].next = insertLoc
                # 元素插入
                self.link[insertLoc].val = ele
                self.link[insertLoc].next = index
                # 首位元素
                self.link[0].next = self.findEmpty()
                sua = 1
                break
            if self.link[index].val is None:
                break
            pre = index
        return sua

    # 查找线性表某位置的元素
    def getByIndex(self, ind):
        if ind  1 or ind >= self.size - 1:
            return -1

        index = self.link[self.size - 1].next
        if index == 0:
            return -1
        for i in range(1, ind):
            index = self.link[index].next

        return self.link[index].val

        # 查找线性表的元素所在位置
    def locateElement(self, ele):
        index = self.link[self.size - 1].next
        ind = -1
        if index == 0:
            return ind
        for i in range(1, self.size - 1):
            if self.link[index].val == ele:
                ind = i
                break
            if self.link[index].val is None:
                break
            index = self.link[index].next
        return ind

        # 删除线性表指定位置的元素
    def deleteElement(self, ind):
        sua = -1
        # 前一个索引
        pre = self.size - 1
        for i in range(1, self.size - 1):
            index = self.link[pre].next
            # 当前位置是个空位置
            if self.link[index].val is None:
                break
            # 已经遍历到第i个位置
            if i == ind:
                self.link[pre].next = self.link[index].next
                self.link[index].val = None
                # 删除元素的游标指向备用链表
                self.link[index].next = self.link[0].next
                # 首位元素
                self.link[0].next = index
                sua = 1
                break
            pre = index
        return sua

        # 按照线性表排序线性表遍历
    def travelLink(self):
        print("*" * 50)
        index = self.link[self.size - 1].next
        while self.link[index].val:
            print(
                f"value = {self.link[index].val} next = {self.link[index].next}"
            )
            index = self.link[index].next
        print("*" * 50)

    # 按照索引遍历
    def traversingByIndex(self):
        print("*" * 50)
        for i in range(self.size):
            print(
                f"index = {i}, value = {self.link[i].val} next = {self.link[i].next}"
            )
        print("*" * 50)


if __name__ == '__main__':
    ll = SLinkList()
    ll.traversingByIndex()
    print(ll.isEmpty())
    print(ll.insert(1, 'A'))
    ll.travelLink()
    print(ll.insert(2, 'B'))
    ll.travelLink()
    print(ll.insert(1, 'C'))
    print(ll.insert(4, 'D'))
    ll.travelLink()
    ll.traversingByIndex()
    print(ll.deleteElement(3))
    ll.traversingByIndex()
    ll.travelLink()
    print(ll.isEmpty())
    print(ll.getByIndex(2))
    print(ll.locateElement('BcA'))
    print(ll.clearSLL())