输入一个链表,按链表值从尾到头的顺序返回一个ArrayList。
一种方法是利用栈来实现;
另外一种方法是利用三个指针把链表反转,关键是 r 指针保存断开的节点。
/**
* 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) {
if(listNode == null)
return new ArrayList<Integer>();
ListNode head = listNode;
ListNode cur = listNode.next;
while( cur!= null){
ListNode temp = cur.next;
cur.next = head;
head = cur;
cur = temp;
}
//此时listNode的next还指向第二个node,所以要让listNode.next=null,防止循环
listNode.next = null;
ArrayList<Integer> res = new ArrayList<Integer>();
while(head !=null){
res.add(head.val);
head = head.next;
}
return res;
}
}
版权属于: 尾尾部落
原文地址: https://cloud.tencent.com/developer/article/1327748
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