wanderindev

from typing import Any, Union


class Node:
    """A linked list node implementation"""

    def __init__(self, node_data: Any) -> None:
        """Initialize the node with the given data and pointing to None"""
        self._data = node_data
        self._next_node = None

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class SinglyLinkedList:
    """A singly linked list implementation"""

    def __init__(self) -> None:
        """Initialize a singly link list where the head is None"""
        self.head = None

    def __str__(self) -> str:
        """Return a string representation of the linked list"""
        sll_nodes = []

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    def get_last_node(self) -> "Node":
        """Return the last node in the linked list"""
        current_node = self.head
        while current_node.next_node is not None:
            current_node = current_node.next_node
        return current_node

    def get_node(self, node_data: Any) -> Union["Node", None]:
        """Return the first node whose data is node_data or None"""
        current_node = self.head

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    def is_empty(self) -> bool:
        """Returns True is the linked list is empty"""
        return not self.head

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    def add_front(self, new_data: Any) -> None:
        """Add a node to the front of the linked list"""
        new_node = Node(new_data)
        new_node.next_node = self.head
        self.head = new_node

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    def add_back(self, new_data: Any) -> None:
        """Add a node to the back of the linked list"""
        self.get_last_node().next_node = Node(new_data)

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    def add_after(self, node_data: Any, new_data: Any) -> None:
        """Add a node after the first node whose data is node_data"""
        new_node = Node(new_data)
        insert_at_node = self.get_node(node_data)
        if insert_at_node:
            new_node.next_node = insert_at_node.next_node
            insert_at_node.next_node = new_node

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    def add_before(self, node_data: Any, new_data: Any) -> None:
        """Add a node before the first node whose data is node_data"""
        new_node = Node(new_data)
        insert_at_node = self.get_prev_node(node_data)
        if insert_at_node:
            new_node.next_node = insert_at_node.next_node
            insert_at_node.next_node = new_node
        else:
            self.add_front(new_data)

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    def pop(self) -> Union[Any, None]:
        """Return and remove the node at the front of the linked list"""
        if self.is_empty():
            return None
        node_to_pop = self.head
        self.head = self.head.next_node
        return node_to_pop.data

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    def remove(self, node_data: Any) -> None:
        """Remove the first node whose data is node_data"""
        if not self.is_empty():
            prev_node = self.get_prev_node(node_data)
            prev_node.next_node = prev_node.next_node.next_node