这道题值得注意的是返回不能返回null,要返回一个空数组;
切记切记;
/** * public class ListNode { * int val; * ListNode next = null; * * ListNode(int val) { * this.val = val; * } * } * */ import java.util.ArrayList; public class Solution { public ArrayList<Integer> printListFromTailToHead(ListNode listNode) { ArrayList<Integer> result=new ArrayList<>(); if(listNode==null){ return result; } ListNode first=listNode; ListNode second=first.next; first.next=null; ListNode third; while(second!=null){ third=second.next; second.next=first; first=second; second=third; } listNode=first; while(listNode!=null){ result.add(listNode.val); listNode=listNode.next; } return result; } }