国际化安全

一面

项目

用到的中间件

基础知识

更新数据库，刷新缓存，通知下游，怎么保持一致性

futuretask

代码

反转链表

//TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or
// click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.

class Node {
    int val;
    Node next;
}

public Node reverse(Node head) {

    Node prev = null;
    Node cur = head;

    while (cur != null) {
        Node next = cur.next;
        cur.next = prev;
        prev = cur;
        cur = next;
    }

    return prev;
}

void main() {
    //TIP Press <shortcut actionId="ShowIntentionActions"/> with your caret at the highlighted text
    // to see how IntelliJ IDEA suggests fixing it.

    Node head = new Node();
    head.val = 1;
    Node head1 = new Node();
    head1.val = 2;
    Node head2 = new Node();
    head2.val = 3;
    head.next = head1;
    head1.next = head2;

    Node ans = reverse(head);

    for (Node p = ans; p != null; p = p.next) {
        System.out.println(p.val);
    }

}

用本地IDE写的，不知道IDEA试用期有多久，一会我搞个盗版装上吧。

挂

配送引擎

一面

项目

稳定性保障

代码

数据流取中位数，用两个优先队列实现。

//TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or
// click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.

PriorityQueue<Integer> qMin = new PriorityQueue<>(),
        qMax = new PriorityQueue<>((o1, o2) -> o2 - o1);

void main() {
    //TIP Press <shortcut actionId="ShowIntentionActions"/> with your caret at the highlighted text
    // to see how IntelliJ IDEA suggests fixing it.

    int[] a = {10,9,8,7,6,5,4,3,2,1};

    for (int i = 0; i < a.length; i++) {
        add(a[i]);
        System.out.println(getMid());
    }

}

void add(int n) {
    qMax.offer(n);
    qMin.offer(qMax.poll());

    if (qMin.size() > qMax.size()) {
        qMax.offer(qMin.poll());
    }
}

double getMid() {
    if (qMax.isEmpty()) {
        return 0;
    }
    if (qMax.size() > qMin.size()) {
        return qMax.peek();
    }
    return (qMax.peek() + qMin.peek()) / 2.0;
}

问题

优先队列的底层实现
秒杀系统如何保证库存一致性