added the linkedlist class

Author: ZabihollahNamazi

Sprint-2/implement_lru_cache/lru_cache.py

@@ -3,7 +3,56 @@ def __init__(self, key, value):
         self.key = key 
         self.value = value 
         self.previous = None
-        self.next = None        
+        self.next = None
+
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value) -> Node:
+        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 remove(self, node: Node) -> None:
+        if node is None:
+            return
+
+        if node == self.head:
+            self.head = node.next
+            
+        if node == self.tail:
+            self.tail = node.previous
+
+        if node.previous is not None:
+            node.previous.next = node.next
+            
+        if node.next is not None:
+            node.next.previous = node.previous
+
+        node.next = None
+        node.previous = None
+
+    def pop_tail(self):
+        if self.tail is None:
+            return None
+        
+        last_node = self.tail
+        value = last_node.value
+        
+        self.remove(last_node)
+        
+        return value        
 
 class LruCache:
     def __init__(self, limit: int):