From 85f1f87c8dcb62daef1d1e94e81e115be96035bd Mon Sep 17 00:00:00 2001
From: marina <138340846+bt3gl-cryptographer@users.noreply.github.com>
Date: Mon, 7 Aug 2023 16:22:14 -0700
Subject: [PATCH] Update flatten_list.py

---
 linked_lists/flatten_list.py | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/linked_lists/flatten_list.py b/linked_lists/flatten_list.py
index 278acdb..b4e7900 100644
--- a/linked_lists/flatten_list.py
+++ b/linked_lists/flatten_list.py
@@ -27,14 +27,15 @@ def dfs(prev, node):
         return dfs(last, temp_next)
 
 
-    def flatten(head):
+def flatten(head):
         
         if head is None:
             return head
 
-        pseudo_head = Node(None, None, head, None)
-      
-        dfs(pseudo_head, head)
-        pseudo_head.next.prev = None
-      
-        return pseudo_head.next
+        sentinel = Node(None, None, head, None)
+    
+        dfs(prev=sentinel, node=head)
+
+        # erase the pointer to sentinel and return
+        sentinel.next.prev = None 
+        return sentinel.next