Update 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

@@ -186,21 +186,20 @@ Python：
 
 class Solution:
     def swapPairs(self, head: ListNode) -> ListNode:
-        res = ListNode(next=head)
-        pre = res
+        dummy_head = ListNode(next=head)
+        current = dummy_head
         
-        # 必须有pre的下一个和下下个才能交换，否则说明已经交换结束了
-        while pre.next and pre.next.next:
-            cur = pre.next
-            post = pre.next.next
+        # 必须有cur的下一个和下下个才能交换，否则说明已经交换结束了
+        while current.next and current.next.next:
+            temp = current.next # 防止节点修改
+            temp1 = current.next.next.next
             
-            # pre，cur，post对应最左，中间的，最右边的节点
-            cur.next = post.next
-            post.next = cur
-            pre.next = post
+            current.next = current.next.next
+            current.next.next = temp
+            temp.next = temp1
+            current = current.next.next
+        return dummy_head.next
 
-            pre = pre.next.next
-        return res.next
 ```
 
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