Merge pull request #2155 from yifanliuu/patch-1

新增python解法递归版 0024.两两交换链表中的节点.md

problems/0024.两两交换链表中的节点.md

@@ -177,6 +177,30 @@ class Solution {
 ```
 
 Python：
+```python
+# 递归版本
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+
+class Solution:
+    def swapPairs(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if head is None or head.next is None:
+            return head
+
+        # 待翻转的两个node分别是pre和cur
+        pre = head
+        cur = head.next
+        next = head.next.next
+        
+        cur.next = pre  # 交换
+        pre.next = self.swapPairs(next) # 将以next为head的后续链表两两交换
+         
+        return cur
+```
+
 ```python
 # Definition for singly-linked list.
 # class ListNode: