Implement doubly-linked list with O(1) operations

Author: RahwaZeslusHaile

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,57 @@
+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 is 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 is None:
+            raise IndexError("pop_tail from empty linked list")
+        
+        value = self.tail.value
+        
+        if self.head == self.tail:
+            self.head = None
+            self.tail = None
+        else:
+            self.tail = self.tail.previous
+            self.tail.next = None
+        
+        return value
+
+    def remove(self, node):
+        if node is None:
+            raise ValueError("Cannot remove None node")
+        
+        if node == self.head == self.tail:
+            self.head = None
+            self.tail = None
+        elif node == self.head:
+            self.head = node.next
+            self.head.previous = None
+        elif node == self.tail:
+            self.tail = node.previous
+            self.tail.next = None
+        else:
+            node.previous.next = node.next
+            node.next.previous = node.previous