Create doubly linkedlist implementation

doubly linkedlist implementation

@@ -0,0 +1,38 @@
+// Given a reference (pointer to pointer) to the head
+// of a DLL and an int, appends a new node at the end
+void append(Node** head_ref, int new_data)
+{
+	// 1. allocate node
+	Node* new_node = new Node();
+
+	Node* last = *head_ref; /* used in step 5*/
+
+	// 2. put in the data
+	new_node->data = new_data;
+
+	// 3. This new node is going to be the last node, so
+	// make next of it as NULL
+	new_node->next = NULL;
+
+	// 4. If the Linked List is empty, then make the new
+	// node as head
+	if (*head_ref == NULL) {
+		new_node->prev = NULL;
+		*head_ref = new_node;
+		return;
+	}
+
+	// 5. Else traverse till the last node
+	while (last->next != NULL)
+		last = last->next;
+
+	// 6. Change the next of last node
+	last->next = new_node;
+
+	// 7. Make last node as previous of new node
+	new_node->prev = last;
+
+	return;
+}
+
+// This code is contributed by shivanisinghss2110