linked list implementation

Author: Mikiyas-STP

Sprint-2/implement_linked_list/linked_list.py

@@ -0,0 +1,52 @@
+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):
+        """Add a value to the head. Return the node as a handle."""
+        node = Node(value)
+        node.next = self.head
+
+        if self.head:
+            self.head.previous = node
+        self.head = node
+        if not self.tail:
+            self.tail = node      #list=empty,tail also points to new node
+        return node
+
+    def pop_tail(self):
+        if not self.tail:
+            return None 
+        value = self.tail.value
+        prev_node = self.tail.previous
+        if prev_node:
+            prev_node.next = None
+        self.tail = prev_node
+
+        
+        if not self.tail:
+            self.head = None #If we removed the only element
+
+        return value
+
+    def remove(self, node):
+        if not node:
+            return
+        prev_node = node.previous
+        next_node = node.next
+        if prev_node:
+            prev_node.next = next_node
+        else:
+            self.head = next_node
+        if next_node:
+            next_node.previous = prev_node
+        else:
+            self.tail = prev_node
+        node.next = None     # Disconnect node
+        node.previous = None