题目

法1:递归写法

class Solution {public ListNode reverseList(ListNode head) {if (head == null || head.next == null) {return head;}ListNode last = reverseList(head.next);head.next.next = head;head.next = null;return last;}
}

法2:迭代写法

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