Update README.md

Author: yanglbme

solution/0200-0299/0206.Reverse Linked List/README.md

@@ -37,13 +37,15 @@
 
 class Solution:
     def reverseList(self, head: ListNode) -> ListNode:
-        pre, p = None, head
-        while p:
-            q = p.next
-            p.next = pre
-            pre = p
-            p = q
-        return pre
+        previous, current, next = None, head, None
+        
+        while current is not None:
+            next = current.next
+            current.next = previous
+            previous = current
+            current = next
+        
+        return previous
 ```
 
 ### **Java**