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]

解

class Solution {
    public ListNode reverseList(ListNode head) {
        if(head == null || head.next == null){
            return head;
        }
        ListNode pre = null;
        ListNode cur = head;
        ListNode next = null;
        while(cur != null){
            next = cur.next;
            
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return pre;
    }
}