03_反转链表
反转链表
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。力扣题目链接
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
思路:直接反转
/**
* 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 pre = null;
ListNode cur = head;
while (cur != null) {
ListNode temp = cur.next;
cur.next = pre;
pre = cur;
cur = temp;
}
return pre;
}
}