diff --git a/src/main/java/linkedlist/ReverseBetween.java b/src/main/java/linkedlist/ReverseBetween.java
index 6e67f24..9e86470 100644
--- a/src/main/java/linkedlist/ReverseBetween.java
+++ b/src/main/java/linkedlist/ReverseBetween.java
@@ -10,6 +10,7 @@ package linkedlist;
  * 链接：https://leetcode.cn/problems/reverse-linked-list-ii/
  */
 //不会一次遍历来翻转
+//二刷不会
 public class ReverseBetween {
     private void reverseLinkedList(ListNode head) {
         // 也可以使用递归反转一个链表
@@ -92,4 +93,5 @@ public class ReverseBetween {
         // 5. 返回新的链表头
         return dummyNode.next;
     }
+
 }
diff --git a/src/main/java/linkedlist/ReverseKGroup.java b/src/main/java/linkedlist/ReverseKGroup.java
index c34adbe..5f657f9 100644
--- a/src/main/java/linkedlist/ReverseKGroup.java
+++ b/src/main/java/linkedlist/ReverseKGroup.java
@@ -10,4 +10,44 @@ package linkedlist;
  * 链接：https://leetcode.cn/problems/remove-duplicates-from-sorted-list-ii/
  */
 public class ReverseKGroup {
+    // 反转 [head, tail] 这一段，返回新的头和新的尾
+    private ListNode[] reverse(ListNode head, ListNode tail) {
+        ListNode prev = tail.next;
+        ListNode p = head;
+        while (prev != tail) {
+            ListNode nxt = p.next;
+            p.next = prev;
+            prev = p;
+            p = nxt;
+        }
+        // 反转后，tail 变成新头，head 变成新尾
+        return new ListNode[]{ tail, head };
+    }
+
+    public ListNode reverseKGroup(ListNode head, int k) {
+        ListNode dummy = new ListNode(-1);
+        dummy.next = head;             // ←—— 关键：把 dummy.next 指向原始 head
+        ListNode pre = dummy;
+
+        while (true) {
+            // 检查剩余是否至少有 k 个节点
+            ListNode tail = pre;
+            for (int i = 0; i < k; i++) {
+                tail = tail.next;
+                if (tail == null) {
+                    // 不足 k 个，直接返回
+                    return dummy.next;
+                }
+            }
+            ListNode nextGroupHead = tail.next;
+            // 反转 pre.next ... tail 这一段
+            ListNode[] reversed = reverse(pre.next, tail);
+            // 接上前半段：pre → reversedHead
+            pre.next = reversed[0];
+            // reversedTail → nextGroupHead
+            reversed[1].next = nextGroupHead;
+            // 移动 pre 到这一段反转后的尾部，为下一轮做准备
+            pre = reversed[1];
+        }
+    }
 }
diff --git a/src/main/java/linkedlist/SwapPairs.java b/src/main/java/linkedlist/SwapPairs.java
index 863ef35..31be1c2 100644
--- a/src/main/java/linkedlist/SwapPairs.java
+++ b/src/main/java/linkedlist/SwapPairs.java
@@ -8,7 +8,8 @@ package linkedlist;
 
  */
 //需重做
-public class SwapPairs {
+//二刷会做
+ public class SwapPairs {
     //只有一个节点或没有节点时无需交换！
     //递归
     public ListNode swapPairs(ListNode head) {
@@ -38,4 +39,20 @@ public class SwapPairs {
         }
         return dummyHead.next;
     }
+
+    public ListNode swapPairs2(ListNode head) {
+        if(head==null || head.next==null) return head;
+        ListNode dummyNode=new ListNode(-1);
+        ListNode pre=dummyNode,cur=head,next=head.next;
+        while (next!=null){
+            cur.next=next.next;
+            next.next=cur;
+            pre.next=next;
+            pre=cur;
+            cur=pre.next;
+            if(cur==null)break;
+            else next=cur.next;
+        }
+        return dummyNode.next;
+    }
 }