高频考题

方法一:

三指针

  1. class Solution {
  2.     //顺序
  3.     public ListNode reverseList(ListNode head) {
  4.         if (head == null || head.next == null) {
  5.             return head;
  6.         }
  7.         ListNode pre = null, now = head, next = null;
  8.         while (now != null) {
  9.             next = now.next;
  10.             now.next = pre;
  11.             pre = now;
  12.             now = next;
  13.         }
  14.         return pre;
  15.     }
  16. }

方法二：

  1. 递归