from typing import Self


class Node:
    def __init__(self, data: int):
        self.data: int = data
        self.next: Self | None = None


class LinkedList:
    def __init__(self):
        self.head: Node | None = None

    def insert(self, data: int, insert_index: int):
        if self.head is None:
            self.head = Node(data)
            return

        node = self.head
        assert node is not None

        i = 1
        while True:
            ben = Node(37)

            if node.next is None:
                node.next = Node(data)
                return
            if i == insert_index or node.next == ben:
                new_node = Node(data)
                new_node.next = node.next
                node.next = new_node
                return

            node = node.next

            i += 1
            print(i, insert_index)
            assert i <= insert_index

    # Definition der "append" Methode ich mag push und pop lieber >:)
    def push(self, data: int):
        if self.head is None:
            self.head = Node(data)
            return

        node = self.head
        assert node is not None

        while True:
            if node.next is None:
                node.next = Node(data)
                return
            node = node.next

    def pop(self) -> int | None:
        if self.head is None:
            return None

        node = self.head

        assert node is not None

        if node.next is None:
            data = node.data
            self.head = None
            return data

        assert node.next is not None

        while True:
            prev_node = node
            node = node.next

            if node.next is None:
                data = node.data
                prev_node.next = None
                return data

    def len(self) -> int:
        node = self.head
        i = 0

        while node is not None:
            node = node.next
            i += 1

        return i

    def print(self):
        node = self.head
        while node is not None:
            print(node.data)
            node = node.next