doubly linked list: add dataclass and typing (#12647)

* Node is a dataclass

* fix mypy errors

* LinkedList is a dataclass

* fix mypy errors

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

* Update doubly_linked_list_two.py

---------

Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>

data_structures/linked_list/doubly_linked_list_two.py

@@ -9,25 +9,19 @@
      Delete operation is more efficient
 """
 
+from dataclasses import dataclass
+from typing import Self
 
+
+@dataclass
 class Node:
-    def __init__(self, data: int, previous=None, next_node=None):
+    data: int
-        self.data = data
+    previous: Self | None = None
-        self.previous = previous
+    next: Self | None = None
-        self.next = next_node
 
     def __str__(self) -> str:
         return f"{self.data}"
 
-    def get_data(self) -> int:
-        return self.data
-
-    def get_next(self):
-        return self.next
-
-    def get_previous(self):
-        return self.previous
-
 
 class LinkedListIterator:
     def __init__(self, head):
@@ -40,30 +34,30 @@ class LinkedListIterator:
         if not self.current:
             raise StopIteration
         else:
-            value = self.current.get_data()
+            value = self.current.data
-            self.current = self.current.get_next()
+            self.current = self.current.next
             return value
 
 
+@dataclass
 class LinkedList:
-    def __init__(self):
+    head: Node | None = None  # First node in list
-        self.head = None  # First node in list
+    tail: Node | None = None  # Last node in list
-        self.tail = None  # Last node in list
 
     def __str__(self):
         current = self.head
         nodes = []
         while current is not None:
-            nodes.append(current.get_data())
+            nodes.append(current.data)
-            current = current.get_next()
+            current = current.next
         return " ".join(str(node) for node in nodes)
 
     def __contains__(self, value: int):
         current = self.head
         while current:
-            if current.get_data() == value:
+            if current.data == value:
                 return True
-            current = current.get_next()
+            current = current.next
         return False
 
     def __iter__(self):
@@ -71,12 +65,12 @@ class LinkedList:
 
     def get_head_data(self):
         if self.head:
-            return self.head.get_data()
+            return self.head.data
         return None
 
     def get_tail_data(self):
         if self.tail:
-            return self.tail.get_data()
+            return self.tail.data
         return None
 
     def set_head(self, node: Node) -> None:
@@ -103,18 +97,20 @@ class LinkedList:
         node_to_insert.next = node
         node_to_insert.previous = node.previous
 
-        if node.get_previous() is None:
+        if node.previous is None:
             self.head = node_to_insert
         else:
             node.previous.next = node_to_insert
 
         node.previous = node_to_insert
 
-    def insert_after_node(self, node: Node, node_to_insert: Node) -> None:
+    def insert_after_node(self, node: Node | None, node_to_insert: Node) -> None:
+        assert node is not None
+
         node_to_insert.previous = node
         node_to_insert.next = node.next
 
-        if node.get_next() is None:
+        if node.next is None:
             self.tail = node_to_insert
         else:
             node.next.previous = node_to_insert
@@ -136,27 +132,27 @@ class LinkedList:
     def get_node(self, item: int) -> Node:
         node = self.head
         while node:
-            if node.get_data() == item:
+            if node.data == item:
                 return node
-            node = node.get_next()
+            node = node.next
         raise Exception("Node not found")
 
     def delete_value(self, value):
         if (node := self.get_node(value)) is not None:
             if node == self.head:
-                self.head = self.head.get_next()
+                self.head = self.head.next
 
             if node == self.tail:
-                self.tail = self.tail.get_previous()
+                self.tail = self.tail.previous
 
             self.remove_node_pointers(node)
 
     @staticmethod
     def remove_node_pointers(node: Node) -> None:
-        if node.get_next():
+        if node.next:
             node.next.previous = node.previous
 
-        if node.get_previous():
+        if node.previous:
             node.previous.next = node.next
 
         node.next = None