二刷206

Author: diguage

docs/0206-reverse-linked-list.adoc

@@ -20,11 +20,39 @@ Reverse a singly linked list.
 
 A linked list can be reversed either iteratively or recursively. Could you implement both?
 
+== 思路分析
 
+image::images/0206-01.png[{image_attr}]
 
 [[src-0206]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0206_ReverseLinkedList.java[tag=answer]
 ----
+--
 
+二刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0206_ReverseLinkedList_2.java[tag=answer]
+----
+--
+====
+
+== 思考题
+
+可以尝试一下递归！
+
+另外，思考一下如何通过传参来简化代码。
+
+== 参考资料
+
+. https://leetcode.cn/problems/reverse-linked-list/solutions/551596/fan-zhuan-lian-biao-by-leetcode-solution-d1k2/?envType=study-plan-v2&envId=selected-coding-interview[206. 反转链表 - 官方题解^]
+. https://leetcode.cn/problems/reverse-linked-list/solutions/2361282/206-fan-zhuan-lian-biao-shuang-zhi-zhen-r1jel/?envType=study-plan-v2&envId=selected-coding-interview[206. 反转链表 - 双指针，清晰图解^]

docs/images/0206-01.png

@@ -469,6 +469,11 @@
 |{doc_base_url}/0343-integer-break.adoc[题解]
 |动态规划
 
+|{counter:codes}
+|{leetcode_base_url}/reverse-linked-list/[206. Reverse Linked List^]
+|{doc_base_url}/0206-reverse-linked-list.adoc[题解]
+|递给解法非常妙！
+
 |===
 
 截止目前，本轮练习一共完成 {codes} 道题。

logbook/202406.adoc

@@ -36,20 +36,22 @@ public class _0206_ReverseLinkedList {
      * Runtime: 0 ms, faster than 100.00% of Java online submissions for Reverse Linked List.
      *
      * Memory Usage: 38 MB, less than 6.48% of Java online submissions for Reverse Linked List.
+     *
+     * @author D瓜哥 · https://www.diguage.com
+     * @since 2020-01-12 12:47
      */
     public ListNode reverseList(ListNode head) {
-        if (Objects.isNull(head)) {
-            return null;
-        }
-        ListNode result = null;
-        ListNode current = head;
-        while (Objects.nonNull(current)) {
-            ListNode pre = current.next;
-            current.next = result;
-            result = current;
-            current = pre;
-        }
-        return result;
+      if (head == null || head.next == null) {
+        return head;
+      }
+      ListNode curr = null;
+      while (head != null) {
+        ListNode next = head.next;
+        head.next = curr;
+        curr = head;
+        head = next;
+      }
+      return curr;
     }
 
     /**

src/main/java/com/diguage/algo/leetcode/_0206_ReverseLinkedList.java

@@ -0,0 +1,24 @@
+package com.diguage.algo.leetcode;
+
+import com.diguage.algo.util.ListNode;
+
+public class _0206_ReverseLinkedList_2 {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2024-09-13 16:24:00
+   */
+  public ListNode reverseList(ListNode head) {
+    return reverseList(head, null);
+  }
+
+  public ListNode reverseList(ListNode head, ListNode pre) {
+    if (head == null) {
+      return pre;
+    }
+    ListNode result = reverseList(head.next, head);
+    head.next = pre;
+    return result;
+  }
+  // end::answer[]
+}