From d4ca92cf66759d30481ced7723639b8984f3c2e2 Mon Sep 17 00:00:00 2001
From: Aida Eslami <ayda.eslami@gmail.com>
Date: Sun, 1 Mar 2026 18:38:04 +0000
Subject: [PATCH 1/2] implement linked list with O(1) operations

---
 Sprint-2/implement_linked_list/linked_list.py | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py
index e69de29..a712132 100644
--- a/Sprint-2/implement_linked_list/linked_list.py
+++ b/Sprint-2/implement_linked_list/linked_list.py
@@ -0,0 +1,51 @@
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.previous = None
+        self.next = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value):
+        new_node = Node(value)
+
+        new_node.next = self.head
+        if self.head:
+            self.head.previous = new_node
+
+        self.head = new_node
+
+        if self.tail is None:
+            self.tail = new_node
+
+        return new_node
+
+    def pop_tail(self):
+        if self.tail is None:
+            return None
+
+        removed = self.tail
+
+        if self.tail.previous:
+            self.tail = self.tail.previous
+            self.tail.next = None
+        else:
+            self.head = None
+            self.tail = None
+
+        return removed.value
+
+    def remove(self, node):
+        if node.previous:
+            node.previous.next = node.next
+        else:
+            self.head = node.next
+
+        if node.next:
+            node.next.previous = node.previous
+        else:
+            self.tail = node.previous
\ No newline at end of file

From eef38b3648ed001c17f9cf7667ce2fea0cca80a0 Mon Sep 17 00:00:00 2001
From: Aida Eslami <ayda.eslami@gmail.com>
Date: Sun, 1 Mar 2026 20:52:11 +0000
Subject: [PATCH 2/2] implement doubly linked list

---
 Sprint-2/implement_linked_list/linked_list.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py
index a712132..d4ee971 100644
--- a/Sprint-2/implement_linked_list/linked_list.py
+++ b/Sprint-2/implement_linked_list/linked_list.py
@@ -16,12 +16,10 @@ def push_head(self, value):
         new_node.next = self.head
         if self.head:
             self.head.previous = new_node
-
-        self.head = new_node
-
-        if self.tail is None:
+        else:
             self.tail = new_node
 
+        self.head = new_node
         return new_node
 
     def pop_tail(self):
@@ -44,6 +42,8 @@ def remove(self, node):
             node.previous.next = node.next
         else:
             self.head = node.next
+            if self.head:
+                self.head.previous = None
 
         if node.next:
             node.next.previous = node.previous