从尾到头打印链表

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题目：

题解：

1、方法一：使用辅助栈实现

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {

    LinkedList<Integer> stack = null;

    public int[] reversePrint(ListNode head) {
        stack = new LinkedList<Integer>();
        while (!(head == null)){
            stack.push(head.val);
            head = head.next;
        }
        int[] a = new int[stack.size()];
        for (int i = 0; i < a.length; i++) {
                a[i] = stack.pop();
        }
        return a;
    }
}

方法二：使用递归实现（从后往前将链表中的数据放入list里）

class Solution2 {

    ArrayList<Integer> tmp = new ArrayList<>();

    public int[] reversePrint(ListNode head) {
        recur(head);
        int[] a = new int[tmp.size()];
        for (int i = 0; i < a.length; i++) {
            a[i] = tmp.get(i);
        }
        return a;
    }

    void recur(ListNode head) {
        if (head == null) return;
        recur(head.next);
        tmp.add(head.val);
    }
}