class Element:
    def __init__(self, data):
        self.data = data
        self.next = None

    # Rekursive Methode zur Berechnung der Länge der Liste
    def length(self):
        if self.next is None:
            return 1
        else:
            return 1 + self.next.length()

    # Entfernt iterativ das erste gefundene Elemente mit dem Wert value aus der Liste
    def remove(self,value):
        previous = self
        current = self.next
        while current is not None:
            if current.data == value:
                previous.next = current.next
            previous = previous.next
            current = current.next

    # Rekursive Methode zur Entfernung des letzten Elements
    def remove_last(self):
        if self.next.next is not None:
            self.next.remove_last()
        else:
            self.next = None


class Liste:
    def __init__(self):
        self.head = None

    # Einfügen eines Elements mit Wert value am Anfang der Liste
    def insert(self, value):
        new_element = Element(value)
        new_element.next = self.head
        self.head = new_element

    # Entfernt das erste Element aus der Liste
    def remove_first(self):
        if self.head is not None:
            value = self.head.data
            self.head = self.head.next
            return value

    # Methode zur Darstellung der Liste
    def show_list(self):
        current = self.head
        while current is not None:
            print(current.data)
            current = current.next
        print("---")

    # Bestimmt rekursiv die Länge der Liste
    def length(self):
        if self.head is None:
            return 0
        else:
            return self.head.length()

    # Sucht nach einem Element mit dem Wert value und gibt den Wert zurück
    def search(self, value):
        current = self.head
        while current is not None:
            if current.data == value:
                return current
            current = current.next
        return None

    # Fügt ein Element mit Wert value vor einem Element mit Wert compValue ein
    def insert_before(self, value, comp_value):
        new_element = Element(value)
        if self.head is None:
            return
        if self.head.data == comp_value:
            new_element.next = self.head
            self.head = new_element
            return
        current = self.head
        while current.next is not None and current.next.data != comp_value:
            current = current.next
        if current.next is not None:
            new_element.next = current.next
            current.next = new_element

    # Rekursive Methode zur Entfernung des letzten Elements
    def remove_last(self):
        if self.head is not None:
            if self.head.next is not None:
                self.head.remove_last()
            else:
                self.head = None

    # Iterative Methode zur Entfernung des letzten Elements
    def remove_last2(self):
        current = self.head
        if current is None:
            return
        elif current.next is None:
            self.head = None
            return
        else:
            previous = self.head
            current = current.next
            while current.next is not None:
                previous = current
                current = current.next
            previous.next = None
            return

    # Rekursive Methode zur Entfernung eines Elements mit Wert value
    def remove(self,value):
        if self.head is None:
            return
        if self.head.data == value:
            self.head = self.head.next
        else:
            self.head.remove(value)

    # Iterative Methode zur Entfernung eines Elements mit Wert value
    def remove2(self, value):
        if self.head is None:
            return
        if self.head.data == value:
            self.head = self.head.next
            return
        previous = self.head
        current = previous.next
        while current is not None:
            if current.data == value:
                previous.next = current.next
                return
            previous = previous.next
            current = current.next

    # Sortiert rekursiv eine Liste nachträglich
    def sub_sort(self):
        if self.head is not None:
            value = self.remove_first()
            self.sub_sort()
            self.insert_sorted(value)

    # Hilfsfunktion zu sub_sort, welches ein neues Element mit Wert value sortiert in eine bestehende Liste einsortiert
    def insert_sorted(self, value):
        new_element = Element(value)
        if self.head is None:
            self.head = new_element
        elif self.head.data > value:
            new_element.next = self.head
            self.head = new_element
        else:
            current = self.head
            while current.next is not None and current.next.data < value:
                current = current.next
            new_element.next = current.next
            current.next = new_element