code for linked_list.py

Author: sheetalkharab

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,51 @@
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.previous = None
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+    def push_head(self, value):
+        new_node = Node(value)  # <-- Node must exist
+        if not self.head:
+            self.head = 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 not self.tail:
+            return None
+        value = self.tail.value
+        if self.head == self.tail:
+            self.head = self.tail = None
+        else:
+            self.tail = self.tail.previous
+            self.tail.next = None
+        return value
+
+    def remove(self, node):
+        if node is self.head:
+            self.head = node.next
+            if self.head:
+                self.head.previous = None
+
+        if node is self.tail:
+            self.tail = node.previous
+            if self.tail:
+                self.tail.next = None
+
+        if node.previous:
+            node.previous.next = node.next
+
+        if node.next:
+            node.next.previous = node.previous
+
+        node.previous = node.next = None
+