From 12037f1fce33fbf49cb616b829c72b6bb309dc4b Mon Sep 17 00:00:00 2001
From: Wonder <hezhaohui0807@163.com>
Date: Fri, 3 Oct 2025 11:32:31 +0800
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+# 反转链表
+
+## 题目
+
+给你单链表的头节点 head ，请你反转链表，并返回反转后的链表。
+ 
+
+示例 1：
+
+
+输入：head = [1,2,3,4,5]
+输出：[5,4,3,2,1]
+示例 2：
+
+
+输入：head = [1,2]
+输出：[2,1]
+示例 3：
+
+输入：head = []
+输出：[]
+ 
+
+提示：
+
+链表中节点的数目范围是 [0, 5000]
+-5000 <= Node.val <= 5000
+ 
+
+进阶：链表可以选用迭代或递归方式完成反转。你能否用两种方法解决这道题？
+
+## 思路
+
+- 初始化
+  - 设置虚拟头结点 `dummyHead`
+- 头插法
+  - 将新来的元素插在虚拟头结点和当前节点之间
+
+
+## 代码
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    public ListNode reverseList(ListNode head) {
+        // Special
+        if (head == null) {
+            return null;
+        }
+        
+        // Init: dummyHead
+        ListNode dummyHead = new ListNode(-1, null);
+
+        // Traverse: Insert
+        while (head != null) {
+            ListNode tmp = head.next;
+            head.next = dummyHead.next;
+            dummyHead.next = head;
+            head = tmp;
+        }
+
+        return dummyHead.next;
+
+    }
+}
+```
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