206. 反转链表

r囧r小猫 2022-09-08 00:19 168阅读 0赞

[https://leetcode-cn.com/problems/reverse-linked-list/][https_leetcode-cn.com_problems_reverse-linked-list]

难度简单1915

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：**

![1479f99ec2d8583971cc3dfb0c59e0cb.png][]

输入：head = [1,2,3,4,5]
    输出：[5,4,3,2,1]

**示例 2：**

![1b87f6d74f7125930f57958e210e996b.png][]

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？

通过次数662,267提交次数917,373

/**
     * 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) {
            ListNode newHead = new ListNode(); //新头节点
            ListNode node = head;
            while(head!=null)
            {
                node = head.next;
                head.next = newHead.next;
                newHead.next = head;
                head = node;
    
            }
            return newHead.next;
        }
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16][]

[https_leetcode-cn.com_problems_reverse-linked-list]: https://leetcode-cn.com/problems/reverse-linked-list/
[1479f99ec2d8583971cc3dfb0c59e0cb.png]: /images/20220829/1faa0f99ee564a328dc8c21d952cfa28.png
[1b87f6d74f7125930f57958e210e996b.png]: /images/20220829/f762cdaf9dd14382bdcae7b837e621ed.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16]: /images/20220829/cb383eb01cd045988f626b7f29d6c88f.png