四刷206

Author: diguage

docs/0206-reverse-linked-list.adoc

@@ -31,7 +31,7 @@ image:images/0206-01.jpg[{image_attr}]
 
 *提示：*
 
-* 链表中节点的数目范围是 `+[0, 5000]+`
+* 链表中节点的数目范围是 `[0, 5000]`
 * `+-5000 <= Node.val <= 5000+`
 
 
@@ -69,6 +69,23 @@ include::{sourcedir}/_0206_ReverseLinkedList_2.java[tag=answer]
 ----
 include::{sourcedir}/_0206_ReverseLinkedList_3.java[tag=answer]
 ----
+
+四刷（递归）::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0206_ReverseLinkedList_41.java[tag=answer]
+----
+--
+
+四刷（迭代）::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0206_ReverseLinkedList_42.java[tag=answer]
+----
 --
 ====
 

logbook/202503.adoc

@@ -110,6 +110,11 @@ endif::[]
 |{doc_base_url}/0146-lru-cache.adoc[题解]
 |✅ 链表前后指针操作
 
+|{counter:codes2503}
+|{leetcode_base_url}/reverse-linked-list/[206. 反转链表^]
+|{doc_base_url}/0206-reverse-linked-list.adoc[题解]
+|✅ 两种解法：递归+迭代
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

src/main/java/com/diguage/algo/leetcode/_0206_ReverseLinkedList_3.java

@@ -14,7 +14,7 @@ public ListNode reverseList(ListNode head) {
 
   private ListNode reverseList(ListNode head, ListNode pre) {
     if (head == null) {
-      return head;
+      return pre;
     }
     ListNode result = reverseList(head.next, head);
     head.next = pre;

src/main/java/com/diguage/algo/leetcode/_0206_ReverseLinkedList_41.java

@@ -0,0 +1,25 @@
+package com.diguage.algo.leetcode;
+
+import com.diguage.algo.util.ListNode;
+
+public class _0206_ReverseLinkedList_41 {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-02 15:23:04
+   */
+  public ListNode reverseList(ListNode head) {
+    return reverseList(head, null);
+  }
+
+  private ListNode reverseList(ListNode head, ListNode pre) {
+    if (head == null) {
+      return pre;
+    }
+    ListNode next = head.next;
+    ListNode result = reverseList(next, head);
+    head.next = pre;
+    return result;
+  }
+  // end::answer[]
+}

src/main/java/com/diguage/algo/leetcode/_0206_ReverseLinkedList_42.java

@@ -0,0 +1,22 @@
+package com.diguage.algo.leetcode;
+
+import com.diguage.algo.util.ListNode;
+
+public class _0206_ReverseLinkedList_42 {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-02 15:39:16
+   */
+  public ListNode reverseList(ListNode head) {
+    ListNode prev = null;
+    while (head != null) {
+      ListNode next = head.next;
+      head.next = prev;
+      prev = head;
+      head = next;
+    }
+    return prev;
+  }
+  // end::answer[]
+}