Refactor

Author: AhmedLSayed9

data_structures/linked_list/doubly_linked_list.dart

@@ -11,15 +11,14 @@ class Node<T> {
 class DoubleLinkedList<T> extends Iterable<T> {
   int _length = 0;
 
+  Node<T>? _head, _tail;
+
   @override
   int get length => this._length;
 
   @override
   Iterator<T> get iterator => _LinkedListIterator<T>(this._head);
 
-  Node<T>? _head;
-  Node<T>? _tail;
-
   /// Pseudocode:
   /// - Create a new node with the value passed to the function.
   /// - If the list is empty, set the head and tail to be the newly created node.

data_structures/linked_list/linked_list.dart

@@ -10,15 +10,14 @@ class Node<T> {
 class LinkedList<T> extends Iterable<T> {
   int _length = 0;
 
+  Node<T>? _head, _tail;
+
   @override
   int get length => this._length;
 
   @override
   Iterator<T> get iterator => _LinkedListIterator<T>(this._head);
 
-  Node<T>? _head;
-  Node<T>? _tail;
-
   /// Pseudocode:
   /// - This function should accept a value.
   /// - Create a new node using the value passed to the function.

data_structures/stack/linked_list_stack.dart

@@ -9,6 +9,7 @@ class Node<T> {
 
 class LinkedListStack<T> {
   Node<T>? _head;
+
   int _size = 0;
 
   T? get last => _head?.value;