dustfree's blog

在2020年1月15日左右找人内推简历，第二天收到HR面试邀请，约了2月上旬，面试岗位：Java后台研发实习（广告业务组）。

一面技术面（约60分钟）

Question

On a 2-dimensional grid, there are 4 types of squares:

1 represents the starting square. There is exactly one starting square.
2 represents the ending square. There is exactly one ending square.

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https://leetcode.com/contest/weekly-contest-189

Number of Students Doing Homework at a Given Time

Given two integer arrays startTime and endTime and given an integer queryTime.

The ith student started doing their homework at the time startTime[i] and finished it at time endTime[i].

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线程池

管理线程，避免增加创建线程和销毁线程的资源损耗。因为线程其实也是一个对象，创建一个对象，需要经过类加载过程，销毁一个对象，需要走GC垃圾回收流程，都是需要资源开销的。
提高响应速度。 如果任务到达了，相对于从线程池拿线程，重新去创建一条线程执行，速度肯定慢很多。
重复利用。 线程用完，再放回池子，可以达到重复利用的效果，节省资源。

内存分配

• 程序计数器
• 虚拟机栈（java方法服务）与本地方法栈（native方法服务）
• 堆区 存放实例对象 可达性算法
• 方法区 (已被加载的类信息，常量，静态变量）运行时常量池（方法区一部分）
• 直接内存（NIO）

Question

Build a heap using array. Sort an array by the heap

HTTP协议

HTTP协议是Hyper Text Transfer Protocol（超文本传输协议）。
HTTP使用统一资源标识符（Uniform Resource Identifiers, URI）来传输数据和建立连接。

进程与线程

进程：分配资源的基本单位
线程：独立运行和独立调度的基本单位

Question

Given a sorted integer array without duplicates, return the summary of its ranges.

Example 1:
Input: [0,1,2,4,5,7]
Output: [“0->2”,”4->5”,”7”]
Explanation: 0,1,2 form a continuous range; 4,5 form a continuous range.

Question

We have two special characters. The first character can be represented by one bit 0. The second character can be represented by two bits (10 or 11).

Now given a string represented by several bits. Return whether the last character must be a one-bit character or not. The given string will always end with a zero.

Example 1:
Input:
bits = [1, 0, 0]
Output: True
Explanation:
The only way to decode it is two-bit character and one-bit character. So the last character is one-bit character.