CodeYourFuture · TzeMingHo · Jun 16, 2026 · Jun 17, 2026 · cjyuan · Jun 18, 2026
diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py
@@ -0,0 +1,69 @@
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+        self.previous = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value):
+        new_node = Node(value)
+
+        if self.head == 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):
+
+        if self.tail == None:
+            return None
+
+        return self.remove(self.tail)
+
+    def remove(self, node):
+        if self.head == None and self.tail == None:
+            return
+
+        new_previous = node.previous
+        new_next = node.next
+
+        val = node.value
+
+        if self.head == node and self.tail == node:
+            self.head = None
+            self.tail = None
+        elif self.head == node :
+            new_next.previous = None
+            self.head = new_next
+        elif self.tail == node:
+            new_previous.next = None
+            self.tail = new_previous
+        elif new_next and new_previous:
+            new_previous.next = new_next
+            new_next.previous = new_previous
+
+        node.previous = None
+        node.next = None
+        return val
+
+    def push_tail(self, value):
+        new_node = Node(value)
+
+        if self.tail == None:
+            self.tail = new_node
+            self.head = new_node
+        else:
+            self.tail.next = new_node
+            new_node.previous = self.tail
+            self.tail = new_node
+        return new_node
+
diff --git a/Sprint-2/implement_linked_list/linked_list_test.py b/Sprint-2/implement_linked_list/linked_list_test.py
@@ -1,6 +1,6 @@
 import unittest
 
-from linked_list import LinkedList
+from linked_list import LinkedList, Node
 
 class LinkedListTest(unittest.TestCase):
     def test_pushes_then_pops(self):
@@ -34,6 +34,29 @@ def test_remove_tail(self):
         self.assertIsNone(b.next)
         self.assertIsNone(b.previous)
 
+    def test_push_tail(self):
+        l = LinkedList()
+        a = l.push_tail("a")
+        b = l.push_tail("b")
+
+        self.assertEqual(l.tail, b)
+        self.assertEqual(l.head, a)
+        self.assertIsNone(b.next)
+        self.assertIsNone(a.previous)
+
+    def test_remove_non_exist_node(self):
+        l = LinkedList()
+        a = l.push_tail("a")
+        b = l.push_tail("b")
+        c = Node("c")
+
+        l.remove(c)
+
+        self.assertEqual(l.tail, b)
+        self.assertEqual(l.head, a)
+        self.assertIsNone(b.next)
+        self.assertIsNone(a.previous)
+
 
 if __name__ == "__main__":
     unittest.main()