1.手写代码水仙花数(input 100<=m<n<=999).
private static void print(int m, int n) {
for (int i = m; i <= n; i++) {
int a = i / 100;
int b = (i % 100) / 10;
int c = i % 10;
int total = (int) (Math.pow(a, 3) + Math.pow(b, 3) + Math.pow(c, 3));
if (total == i) {
System.out.println(i);
}
}
}
2.SQL语句,保留相同邮箱最后注册的人.
delete
from test.person
where id not in (select exist
from (select max(id) as exist from test.person group by email) as tmp);
3.秒杀系统的优化. 我个人认为用 mq 削峰,然后直接消费固定数量,最后持久化数据库.
