London | Nadika Zavodovska | Module-Complexity | Sprint 2 | Implement linked list

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,57 @@
+# A single node in the list
+class ListNode:
+    def __init__(self, value):
+        self.value = value
+        self.previous = None
+        self.next = None
+# The linked list class
+class LinkedList:
+    def __init__(self):        
+        self.head = None        
+        self.tail = None
+
+    # Add a value to the front of the list
+    def push_head(self, value):        
+        new_node = ListNode(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
+
+    # Remove and return value from the end
+    def pop_tail(self):
+        if self.tail is None:
+            return None
+
+        value = self.tail.value
+
+        if self.tail.previous:
+            self.tail = self.tail.previous
+            self.tail.next = None
+        else:            
+            self.head = None
+            self.tail = None
+
+        return value
+
+    # Remove a node from the list
+    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
+
+        node.previous = None
+        node.next = None