剑指offer系列：从尾到头打印链表

描述

输入一个链表，按链表从尾到头的顺序返回一个ArrayList。

代码

/** * 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> curlist = new ArrayList<>();
        ArrayList<Integer> ans2 = new ArrayList<>();
        ListNode cur = listNode;
        while (cur!=null) {
           curlist.add(cur.val);
           cur =cur.next;
        }
        for (int i = curlist.size()-1; i >= 0; i--) {
            ans2.add(curlist.get(i));
        }
        return ans2;
    }
}

代码优化

/** * 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> curlist = new ArrayList<>();
        ListNode cur = listNode;
        while (cur!=null) {
           curlist.add(0,cur.val);
           cur =cur.next;
        }
       return curlist;
    }
}