二刷25

Author: diguage

docs/0025-reverse-nodes-in-k-group.adoc

@@ -1,7 +1,7 @@
 [#0025-reverse-nodes-in-k-group]
 = 25. K 个一组翻转链表
 
-https://leetcode.cn/problems/reverse-nodes-in-k-group/[LeetCode - 25. K 个一组翻转链表 ^]
+https://leetcode.cn/problems/reverse-nodes-in-k-group/[LeetCode - 25. K 个一组翻转链表^]
 
 给你链表的头节点 `head`，每 `k` 个节点一组进行翻转，请你返回修改后的链表。
 
@@ -30,14 +30,18 @@ image::images/0025-02.jpg[{image_attr}]
 *提示：*
 
 * 链表中的节点数目为 `n`
-* `+1 <= k <= n <= 5000+`
-* `+0 <= Node.val <= 1000+`
+* `1 \<= k \<= n \<= 5000+`
+* `0 \<= Node.val \<= 1000+`
 
 **进阶：**你可以设计一个只用 stem:[O(1)] 额外内存空间的算法解决此问题吗？
 
 == 思路分析
 
-先统计链表长度，然后根据长度将链表切段，每段使用递归反转链表，最后再接上剩余不够一段的部分。代码如下：
+先统计链表长度，然后根据长度将链表切段，每段使用递归反转链表，最后再接上剩余不够一段的部分。
+
+image::images/0025-10.png[{image_attr}]
+
+也可以从头开始遍历，内层遍历有 K 个元素就反转，否则就直接接上。
 
 [[src-0025]]
 [tabs]
@@ -51,13 +55,19 @@ include::{sourcedir}/_0025_ReverseNodesInKGroup.java[tag=answer]
 ----
 --
 
-// 二刷::
-// +
-// --
-// [{java_src_attr}]
-// ----
-// include::{sourcedir}/_0025_ReverseNodesInKGroup_2.java[tag=answer]
-// ----
-// --
+二刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0025_ReverseNodesInKGroup_2.java[tag=answer]
+----
+--
 ====
 
+
+== 参考资料
+
+. https://leetcode.cn/problems/reverse-nodes-in-k-group/solutions/1992228/you-xie-cuo-liao-yi-ge-shi-pin-jiang-tou-plfs/[25. K 个一组翻转链表 - 【视频讲解】从反转链表到 K 个一组反转^]
+. https://leetcode.cn/problems/reverse-nodes-in-k-group/solutions/248591/k-ge-yi-zu-fan-zhuan-lian-biao-by-leetcode-solutio/[25. K 个一组翻转链表 - 官方题解^]
+. https://leetcode.cn/problems/reverse-nodes-in-k-group/solutions/10416/tu-jie-kge-yi-zu-fan-zhuan-lian-biao-by-user7208t/[25. K 个一组翻转链表 - 图解 K 个一组翻转链表^]

docs/images/0025-10.png

@@ -2024,6 +2024,11 @@ endif::[]
 |{doc_base_url}/0031-next-permutation.adoc[题解]
 |❌ 双指针。看了解题思路，自己写出来的。解题思路还要多推敲。
 
+|{counter:codes2503}
+|{leetcode_base_url}/reverse-nodes-in-k-group/[25. K 个一组翻转链表^]
+|{doc_base_url}/0025-reverse-nodes-in-k-group.adoc[题解]
+|✅ 从头开始遍历，内层遍历有 K 个元素就反转，否则就直接接上。
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

logbook/202503.adoc

@@ -0,0 +1,61 @@
+package com.diguage.algo.leetcode;
+
+import com.diguage.algo.util.ListNode;
+import com.diguage.util.ListNodes;
+
+import java.util.Objects;
+
+public class _0025_ReverseNodesInKGroup_2 {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-12-01 22:32:23
+   */
+  public ListNode reverseKGroup(ListNode head, int k) {
+    ListNode dummy = new ListNode(0);
+    dummy.next = head;
+    ListNode pre = dummy;
+    ListNode cur = head;
+    while (cur != null) {
+      ListNode temp = cur;
+      ListNode next = null;
+      boolean flag = false;
+      for (int i = 0; i < k - 1 && Objects.nonNull(temp.next); i++) {
+        temp = temp.next;
+        if (i == k - 2) {
+          flag = true;
+          next = temp.next;
+          temp.next = null;
+        }
+      }
+
+      if (flag) {
+        pre.next = reverse(cur);
+        pre = cur;
+      } else {
+        pre.next = cur;
+        break;
+      }
+
+      cur = next;
+    }
+    return dummy.next;
+  }
+
+  private ListNode reverse(ListNode head) {
+    ListNode pre = null;
+    while (head != null) {
+      ListNode next = head.next;
+      head.next = pre;
+      pre = head;
+      head = next;
+    }
+    return pre;
+  }
+  // end::answer[]
+
+  static void main() {
+    new _0025_ReverseNodesInKGroup_2()
+      .reverseKGroup(ListNodes.build(1, 2, 3, 4, 5), 2);
+  }
+}