Update 0206.翻转链表.md

Python递归法从后向前

Author: roylx

problems/0206.翻转链表.md

@@ -228,7 +228,22 @@ class Solution:
 
 ```
 
+Python递归法从后向前：
 
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next: return head
+        p = self.reverseList(head.next)
+        head.next.next = head
+        head.next = None
+        return p
+```
 
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