London | 25-SDC-NOV | Jesus del Moral | Sprint 2 | Implement Linked List

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,53 @@
+class Node: #A node in a doubly linked list
+    def __init__(self, value): #Initialize a new node with the given value and no next or previous nodes
+        self.value = value
+        self.previous = None
+        self.next = None
+
+
+class LinkedList: # A doubly linked list data structure
+    def __init__(self): # Initialize an empty linked list with no head node
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value): # Add a new node with the given value to the head of the list
+        new_node = Node(value) # Create a new node with the given value
+
+        new_node.next = self.head # Set the new node's next pointer to the current head of the list
+        if self.head: # If the list is not empty, set the current head's previous pointer to the new node
+            self.head.previous = new_node
+        else:
+            self.tail = new_node
+
+        self.head = new_node # Update the head of the list to be the new node
+        return new_node   # Return node for O(1) removal later
+
+    def remove(self, node): # Remove the given node from the list
+        if node.previous:
+            node.previous.next = node.next
+        else:
+            # Removing head
+            self.head = node.next
+
+        if node.next:
+            node.next.previous = node.previous
+        else:
+            # Removing tail
+            self.tail = node.previous
+
+        # Clean up references
+        node.previous = None
+        node.next = None
+
+    def pop_tail(self):
+        if not self.tail:
+            return None
+
+        old_tail = self.tail
+        value = old_tail.value
+
+        self.remove(old_tail)  # handles pointer updates + cleanup
+
+        return value
+
+

Sprint-2/implement_linked_list/linked_list_test.py

@@ -1,5 +1,4 @@
 import unittest
-
 from linked_list import LinkedList
 
 class LinkedListTest(unittest.TestCase):