Switch to Java development and apply (Toutiao, Pinduoduo, Huawei, NetEase, etc.) and won Toutiao offer

1. Opening

As a second-level major under a civil engineering major of a 211 college, I found that the prospect of this major was worrying through Zhihu in my sophomore year (a life-changing knowledge problem!) and made an early plan to change careers. Thanks to NTU's persistence, I finally got the inter-professional undergraduate program to the NTU Soft Institute. Facts have proved that the school's reputation has brought me a lot of help during the spring recruitment and concealed the inter-professional disadvantage. After the first semester of graduate school, basically after the winter vacation, the spring internship will officially start at the end of February .

Two, before the text

Before the interview , I would like to personally talk about two important off-site factors: interview rhythm and psychological preparation .

1. Interview rhythm

Before we have really experienced an interview, we will definitely think: first go to a small factory to practice hands, and then go to a large factory. However, in fact, it is not the rhythm of small factories first and then big ones, but the rhythm of big and small, big and small. **Big factories and small factories are usually interspersed with interviews, and the big factories are often the first to interview. **This requires us to be fully prepared from the beginning of the spring recruitment-even if the depth may not be enough, the breadth must at least cover most of the knowledge points, so that "even if the bat on March 1st, at least can pass 1 "Face" level. If you are not sure, it is better to delay for two days. The growth in these two days will be very rapid (just like the two days before the final exam). I suffered a big loss myself: Tencent was very inquisitive on the one hand, and I can’t explain both post and get (god knows what I think), so when others Tencent is 2, 3, 4, and 5, I only have this in the whole spring recruitment. One chance-if the performance is too bad, other interviewers won't make it.

Considering that our abilities are gradually increasing over time, I personally feel that it is more appropriate to arrange the company that I want to go to in the middle and late stages of the review. **Of course, the issue of hc must be taken into consideration. Take me as a chestnut. I originally made headlines on the official website in early March, but for various reasons there has been no interview. I missed a collective interview in late March and didn't pass the interview until late April. Compared with the classmates I met in March, I lost the choice of the department, but I was really not confident that I could pass the interview in late March. Moreover, for the company Toutiao, please try to push first. There is no written test, you can choose the department freely. If you are lucky, you can enter on both sides, and finally go to the official website for delivery!

2. Mental preparation

The front of spring recruitment can be drawn from February to May, which is very long. Not only do we need to read books and study, but we also have constant interviews, as well as courses and exams that may be arranged by the school, so mental health is very important. Brothers who have girlfriends hold their girlfriends tightly, and those who don’t have girlfriends hold their roommates tightly (I would like to thank several of my roommates!)

In addition, before the spring recruits, there must be psychological preparations for "immediately facing spring recruits". The ideal timeline is:

• From November to December last year, I realized that I was looking for an internship, and I started to read the questions and read the data (algorithms are the most difficult to attack)
• During the winter vacation there is no project to do a deep project (non-crud), there is a deep mining project of the project (distributed, high concurrency sent to Shangyi, the evil Ali)
• Spring recruits began on March 1, Haitou and preparing for interviews.
• March-April: ( The pre-approval stage of Tencent, Alibaba, NetEase and other big companies, the rolling interview stage of Toutiao, PDD, and other factories also began ) While studying, watching the interviews of the cattle customers, the interview collapsed. Beng, sum up the lessons, and face the next game well. It is recommended to take an offer first, otherwise, the mentality is easy to explode.
• From April to May: ( Official approval from major companies such as Tencent, Ali, headline, rolling interview phase of pdd, Huawei, and blue-green start ) The big guys have already got the offer at this time, and the ones who have been approved in advance like me are cold Just get ready for the formal approval, which is still the intersection of interview and study. **Tencent does not lock your resume, and you can face it if you are caught. Ali can only face one at a stage, choose the department carefully, don't worry about it. **Blue factory can enter as long as one side, the price is too high. Huawei is also very good. I asked the basics in two ways, that is, the personality test is more metaphysical (who would have thought that Haisi was pushed to the forefront of the storm).
• May-June: The big factories basically ended before, but Huawei is an exception. The offer is slow, and the entry is slow. Wait slowly for the prize draw. But at this time, you can still receive calls from departments that are not fully recruited, so you can pick up a miss. I even received an interview call from a department of Ali in the headquarter building of Toutiao (= =)

Three, the text

The following is the order in which I have posted the experience of each factory.

Netease side (mutual entertainment)

• Self introduction + project
• What are the differences and advantages between RPC framework and ordinary http? Based on Tcp encapsulation or http encapsulation
• Is rpc a long connection? If you want to transmit a particularly large file, is the bottom layer still stream-based? What IO model is Nio?
• watch star fork of github
• The difference between exception and error, is oom an error or an exception? What is allocated on the heap and stack?
• Only perform gc on the heap. Is this sentence correct? Call system.gc() and execute gc immediately?
• Page fault interrupt page address translation memory jitter
• Does the fork instruction of linux copy the data immediately?
• What does linux use to see network conditions? What do you use to see logs?
• Congestion control and the algorithm inside? Flow control protocol
• What does the Ping command do? Based on which layer? Which layer is ping?
• The biggest difference between Mysql and Redis? The difference between MyISAM and InnoDB?
• Implementation of Redis. Why is it so high-performance? When the set kv key-value pair is entered, the length of the kv key-value is different. Do you think the underlying data structure is the same? What should I do if the AOF file will be large for a long time with the persistence strategy? Classification of InnoDB row locks (in fact, exclusive locks and shared locks)
• What is the effect of Select from update? How do you usually handle affairs?
• Two queues realize a stack and generate points evenly in the circle (polar coordinate system)
• The underlying implementation of the ps command (???)
• Did the class loader write it yourself?

Netease two sides (mutual entertainment)

• Self-introduction, crawler project function introduction
• Are static web pages crawled or loaded asynchronously? How to crawl asynchronously loaded? How is the performance? What if the performance requirements are high?
• Introduce the principle of coroutine implementation
• When a coroutine is stuck when crawling a website, will the coroutine of the same process be stuck?
• Comparison of the benefits of coroutines and threads
• What problem can the coroutine solve
• Is there a stress test? Under what circumstances need to use coroutine
• The bottom layer implementation of the yield mechanism of the coroutine
• rpc frame full duplex or half duplex unidirectional or bidirectional
• Regardless of how full duplex can be implemented in both directions under half duplex conditions? If you want to achieve two-way, should you use a long connection or a short connection?
• Can half-duplex communication be realized with short connection
• How to obtain the result of an RPC call asynchronously
• Is the communication format of RPC implemented based on javaAPI?
• What communication format have you used? Can these libraries be cross-language?
• What are the technical difficulties of Springboot? What issues should be paid attention to when designing a microservice system? How do you understand microservices?
• The application can scale horizontally, what about the database?
• How does redis ensure cache consistency
• Where microservices will increase complexity exponentially
• Scenario: How to quickly locate a failure in one of a thousand microservices?

Headline Beijing side

PS: Because I passed the Niuke video interview and there was no recording, the replay question was not too complete. This is also my mentor after joining the company.

• Process scheduling
• tcp shakes hands three times and waves four times, why is it four times?
• Algorithm problem: Generate full array, non-recursive middle-order traversal of the binary tree

Headline Beijing Two Sides

• The internal implementation of ThreadLocal. How to determine which threadlocal is used by a thread?
• The internal implementation of sync, and optimization
• What is the difference between the different methods of sync annotation.
• Algorithmic question: Convert the numbers represented by Chinese characters into Arabic numerals (I actually wrote by converting Arabic numerals to Chinese characters, but the logic is fine)
• Application problem: a problem that is implemented in combination mode. Similar to list all files in the folder. (There are many minor problems with handwriting, such as typos and no return value)
• Is there any way to store the database in the tree?

Headlines on three sides of Beijing

• Blow the project. I focused on Netty, startup, connection establishment, NIO features, and applicable scenarios.
• Features of Spring, IOC and AOP
• Database index, transaction
• Algorithm: Minimum edit distance. (Luck, I just got the original problem a few days ago, otherwise it will be cool. Even so, I still missed a condition when writing the transfer equation on the spot)

PS: Toutiao is very efficient. At the end of the day, the results are well received in 5 minutes. However, I voted for the Nanjing backend, and the last offer was the Beijing Big Data Post............I am not really humble, but............In the end, I went to Beijing to read poetry.

Pinduoduo

PS: The pdd written test is really amazing. I was so lucky to make three of them. They passed the written test, but the big guys who made the same three did not have the written test... And the written test was passed in March, and the interview was only scheduled in April after I reminded hr... ………

PS1: But the pdd interview experience is really good, it is really basic. It's much more friendly than Ali's fight!

• Talk about 8 data structures
• The difference between stack and queue
• Examples of stacks in life: I didn’t expect it, this is the only thing I don’t know in the whole interview
• Algorithm question: Oral, or TOPK original question...
• The possible height of a tree of n nodes. Highest and lowest height
• BST tree height
• Project difficulties
• The usage scenario of redis and the difference between memrycache
• The difference between UDP and TCP
• Mysql storage engine and index
• Asked about an order data table (uid, orderId, time, moblie) 2000w per day, it needs to be stored for 1 year. How should I save it?
• Finally, I chatted with me for a few minutes about my career plan! Experience invincibility

Pinduoduo two sides

• Ask the project first. web project background. How to deal with high concurrency and how to do distributed transactions.
• Have you read the source code? AQS and concurentHashMap and HashMap. Let me talk about the differences between the various versions.
• What is the difference between the efficiency of ConcurentHashMap of 1.8 version and HashMap in single thread
• What have you learned about multithreading? Let’s introduce the Netty thread model and the four Java thread pools.
• Nio feature introduction
• How do you self-study read books: the art of concurrent programming
• JMM memory visibility
• What else can guarantee visibility: sync and Lock
• How to interrupt the thread (didn't understand the problem, I got the kill command later)
• Asked my previous written test questions (how can I remember it after more than a month)
• Handwritten code: There is no algorithm, just translate according to the meaning of the question. But I haven’t written for a long time, the writing is very poor, the bug hasn’t been seen yet, and the interviewer has to remind...

PS: Unlike the product of Pinduoduo, which gives people an impression, the interview experience is quite good, and it is not very fairy, maybe it is in the period of rapid development.

other

Blue Factory: On-site. I asked a lot about spring, such as how to solve the problem of interdependence.

Huawei: The interview process is very formal, and a meal is included. If it is not for random separation, Huawei is really good.

Four, summary

During the whole spring recruitment period, I have met all kinds of great gods, especially when others have an offer. I have not yet... Fortunately, at the end of Toutiao and Pinduoduo, I gave an offer that met my psychological expectations. It ended more than 2 months. torment.

But unfortunately, I didn’t get any offer from BAT in the end. Compared with other great gods, the algorithm questions were also not accumulated before, but I passed the interview of Toutiao by luck; every knowledge point is also Without in-depth understanding, I have forgotten most of it after memorizing it; and most importantly, writing less code!

It will be autumn move within two months, fighting!

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