Birmingham | 26-Jul SDC | Merve Reis | Sprint 2 | Implement linked list

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,54 @@
+
+from typing import Optional
+
+
+class Node:
+    __slots__ = ("value", "next", "previous")
+
+    def __init__(self, value: object) -> None:
+        self.value: object = value
+        self.next: Optional["Node"] = None
+        self.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: object) -> Node:
+        new_node = Node(value)
+
+        if self.head is None:
+            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[object]:
+        if self.tail is None:
+            return None
+
+        old_tail = self.tail
+        value = old_tail.value
+        self.remove(old_tail)
+
+        return value
+
+    def remove(self, node: Node) -> None:
+        if node.previous is None:
+            self.head = node.next
+        else:
+            node.previous.next = node.next
+
+        if node.next is None:
+            self.tail = node.previous
+        else:
+            node.next.previous = node.previous
+
+        node.next = None
+        node.previous = None