diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py index e69de29..3732110 100644 --- a/Sprint-2/implement_linked_list/linked_list.py +++ b/Sprint-2/implement_linked_list/linked_list.py @@ -0,0 +1,62 @@ +from dataclasses import dataclass +from typing import Any, Optional +# to reduce memory usage we use slots true to tells Python not to create a dynamic __dict__ for every node, +@dataclass(slots=True) +class Node: + value: Any + next: Optional['Node'] = None + previous: Optional['Node'] = None + + +class LinkedList: + def __init__(self) -> None: + self.head: Optional[Node] = None + self.tail: Optional[Node] = None + + def push_head(self, value: Any) -> Node: + new_node = Node(value) + + if not self.head: + self.head = new_node + self.tail = new_node + else: + new_node.next = self.head + self.head.previous = new_node + self.head = new_node + + return new_node + + def pop_tail(self) -> Optional[Any]: + if not self.tail: + return None + + value_to_return = self.tail.value + self.remove(self.tail) + return value_to_return + + def remove(self, node: Node) -> None: + if not node: + return + + if node == self.head: + self.head = node.next + if self.head: + self.head.previous = None + else: + self.tail = None + + elif node == self.tail: + self.tail = node.previous + if self.tail: + self.tail.next = None + else: + self.head = None + + else: + assert node.previous is not None + assert node.next is not None + node.previous.next = node.next + node.next.previous = node.previous + + node.next = None + node.previous = None