今天这道题是道简单题，使用双指针进行迭代即可，画了下草图如下

代码如下

class Solution {
    public ListNode reverseList(ListNode head) {
        if (head == null || head.next == null) {
            return head;
        }
        ListNode p = head, q = head.next, temp = null;
        while (q != null) {
            p.next = temp;
            temp = p;
            p = q;
            q = q.next;
        }
        p.next = temp;
        return p;
    }
}

题目链接：题单 - 力扣（LeetCode）全球极客挚爱的技术成长平台