London | 26-JUL SDC | Ping Wang | Sprint 2 |Implement linked-list CYF-1180

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,55 @@
+class Node:
+    __slots__ = ("value", "next", "previous")
+
+    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):
+        node = Node(value)
+
+        if self.head is None:
+            self.head = node
+            self.tail = node
+        else:
+            node.next = self.head
+            self.head.previous = node
+            self.head = node
+
+        return node
+
+    def pop_tail(self):
+        node = self.tail
+
+        if node is None:
+            return None
+
+        self.remove(node)
+
+        return node.value
+
+    def remove(self, node):
+        if node == self.head and node == 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
+
+        node.next = None
+        node.previous = None