[剑指offer] 从尾到头打印链表

/**
*    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;
    }
}