S: context, this project's background
T: task, responsible for their own projects in which the local
A: Action (☆), is well aware of the techniques used, such as what is the framework used, why use this, and other frameworks ( technology) compared to the advantages and so on.
R: result (☆), the project achieved what kind of effect, where they have not learned what to think well, what areas could be improved. The company enjoys having people to think for themselves
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one side:
1 to write a title, the median find a disorderly array of
2 wrote a fast row, and then I found a large number of k-disordered array, I said let's find the sort, in fact, you can use fast row partition function.
3 rows of fast time complexity, worst case it is the best case yet, heap sort time complexity of it, the complexity of the construction of the heap is how much, nlgn.
4 understand what operating system, Linux and Windows
5 to talk about Linux disk management, and a look ignorant force
6 Linux-process communication which, five pieces of
how to achieve 7 Linux shared memory, probably said a bit.
8 concrete steps to achieve the shared memory, I say not used
9 socket network programming, talk about the TCP three-way handshake and four waved intermediate network is not good, the interviewer did not hear clearly, very awkward
10 skips network, ask the project something
11 asked me how docker said very clearly, I'm from physical machines, virtual machines to achieve concrete container slightly to say next.
12 asked me specific implementation cgroup in linux will not.
More than 13 threads used which, chm and countdownlatch in practice used
video network speed passenger today's cattle under 14 have to Tucao do not know what reason than a card, obviously download speed is normal ah, cattle passenger per second video only 20k. . Crazy dropped was very boring.
Two faces:
1 self-introduction
2 Java collection classes which are thread-safe
3, respectively, to talk about these collections, how hashmap achieve, pull a lot
to achieve 4 MySQL indexes, innodb index, b + tree index is how to achieve, why does b + tree indexing node, a node stored in many data and how the provisions of the size of the corresponding disk page.
5 MySQL transaction isolation level, respectively, to resolve any problems.
6 Redis understand it, if there are 100 million Redis key, use the command keys will affect the online service, I would say, because it is a single-threaded model, can deploy multiple nodes.
7 Q. I know there is a command that can achieve the above functions. I do not know
the persistence of way 8 Redis, aod and rdb, how to achieve specific, additional log and backup files, then the principle underlying implementation know, is not clear.
9 Redis of the list is how to achieve, I say with ziplist + quicklist implemented, ziplist compression space, quicklist linked list implementation.
10 sortedset how to achieve, using dict + skiplist realized, I asked skiplist data structure, probably to say next is a simple quick query structure.
11 understand what the message queue, rmq and kafka, did not fine to ask
12 questions time to write. The first question: write a sequence traversal.
13 The second question: Write a tree node is inserted into the insertion method a sort of tree, using a recursive way to find the insertion position.
14 third question: a directed graph adjacency matrix, and is the right view in FIG. Analyzing now ask how there ring.
15 I said come directly dfs origin shall have the ring, just started writing when I asked a mouth is not just find one on the line, the interviewer said yes, then I say this should bfs, once access to the original there is a ring node.
16 I do not have a recursive interviewer asks this question can not be done, in fact, I have not started writing. Then I said, no ideas, he suggested that I topology. I did not understand the topology can bring any good. Now I thought, it seems to explain the process can not be found when accessing the next node has a ring. Access should make a mark on it.
Fourth Question 17: a binary tree, binary tree to find the longest path.
I use the high tree seeking ways to obtain the left and right subtrees height of the root node, add up to is.
18 Then the interviewer prompted to consider a sub-tree depth is particularly large, so I used to traverse the maximum refresh mode, complete traversal of a tree that you can use the above method.
19 The interviewer said complexity is relatively high, but due to the time say over.
Three sides:
The interviewer is really high on three sides of the cold ah, even stern, and I asked him to ask him that he did not love Dali, and made my heart Huangde one to feel cool.
1 tell us about the project
2 you talk about concurrency technology, chm and countdownlatch how to use
3 Why should such a deal, use the thread pool is not also possible. I can also say
what operating system the 4-process communication, and orphaned zombie process, how to avoid the zombies, I say let the parent process displayed a notice that the parent process know how the child process is over, do not answer.
5 computer network TCP and UDP What is the difference, why the Thunder download is UDP-based, and I say that FTP is based on TCP, and TCP does not require that the Thunder is p2p guarantee reliable transmission.
And he said no, because I say is not to establish a connection, overhead is relatively large, he said, not
7 I said a lot of the sending node p2p, it is not so various transport needs guarantee, he said wrong.
8 I said automatically subcontractors and TCP TCP can define their own data length. . He still say no.
Finally, he said forget it. We asked the next bar.
Deadlock necessary condition 9 operating system, and how to avoid deadlocks.
10 a write cache LRU, complete elimination of overtime and LRU eliminated.
I said with lhm okay, and he said with linkedlist hashmap
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Side of
the interviewer is very nice, very good talk. He said the interview process is that 1 project, 2 basis (OS, network, composed of principles), 3 algorithm, ok you ask me. Of course, ok, ah ~
I first said under the project, because the undergraduates have not done what , said teachers do a bit of research and projects, is about algorithms, did not feel extra points ...
and then ask Basics:
suppose a big game has 10 + G, memory is only 2G, how to make it go up?
I say it is virtual memory, virtual memory I just say it's design, hr: ah, the ok ~,
WO: balabala ~ ... said virtual memory, CPU over the fight from a command began to explain, I feel pretty good,
HR : Then I asked each process has a page table is still only one. What is the role of two logical space page table, look at the size of the process. Anyway, you asked not answer, or he felt ok up until the
network
to explain a data packet from one subnet to another subnet process, MAC address, how IP transformation, clear
algorithm questions, write code
1) how determining a directed acyclic graph there is no ring (topo)
diameter 2) a binary tree, I told him twice bfs like, he does not believe, but let me prove a bit difficult to prove ... ah
asked a little java-based, let me explain HashMap
HR: the ok, what I would like to ask?
wo: can give an evaluation of it? hr also say ok, said the headline pay greater attention to communication, said this part of my doing okay.
After 3 minutes, 2 surface notice came
two faces
1. Look at your resume only know that I was undergraduate, said he had never been face undergraduates. I wanted to introduce myself.
ACM said that a solution to the most difficult topics
wo: what ??? have retired a year. He says to do on a last newcoder. Explains most of the day good
language,
1) says about the difference between c ++ and java are
here to pull a bunch,
2) cut from c ++ to java to pay attention to what
wo: what? ? ? ? Did not know, you can say elaborate
hr: student1 = student2, java and c ++ what's the difference
wo: finally understand the
3) is too many to understand? ?
Base Print {} class
class Base {Supper exend. . . Print @override ()}
Base b = new new Supper ();
b.printf ();
output of which.
WO: Supper
HR: Why?
Not clear
hr: You can guess what
I said, because b points to memory is supper, and then ...
hr: What do you think this is still running the compiler decide when, based on your answer
w: Runtime
the ok algorithm the
algorithm
1) memory only 1kw, there are 100 million int on disk O (n) to find a large section k.
I said that if I'd have the memory limit is not O (n) approach. He said no, give a hint, the value is even 1 billion to 200 million, after finally prompted me to solve
2) subsequent binary tree traversal non-recursive
3) a pen questions, (looks like they do not know the written test ...)
An open question, he said Chaogang, it should be to refuse me (55555555555 ~)
database exists on a different server, in order to allow different server load balancing, now add a server how to make data move at least. I answered strategy with hash, and then hash hashmap of reference.
hr: what questions to ask me?
wo: evaluation of what I ...
3 3 minutes to surface, a second surface, said third surface is his boss.
on three sides,
3 sides asked quickly, seems to want to know where you are at the upper bound of knowledge.
Introduce
the Java the JVM, JNI, the Spring
WO: I do not know ...
HR: language is the basis of it
w: en ~
algorithm problem
k-th largest, write code, I wrote a quick idea row
network
1) 3-way handshake, 4 waved
me say my three-way handshake, he asked why. I did not answer it,
he does not know can not know, do not mess answer.
2) Then he asked after sliding window congestion. Also asked why, I said to congestion, TCP fair. hr said no. . . Hey every wrong here
asked a more difficult question
to ask me search system, tens of millions of pages, the query how to do,
hey, good answer. Later ate lunch
at lunch and 3 hr face eat together, he asked me some other problems, feeling a little routine
Bixiao province ranked
in graduating students in what is a first-class Internet companies
took a few offer
why not PubMed
well, thanks on a big brother. Here I offer experience
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Ants gold service side:
1. You used the project AOP, AOP that you know about (mainly answered static agents, dynamic proxy, dynamic and static proxy proxy difference, the difference between JDK CGLIB agents and agents),
2. If now allows you to design a distributed cache system, how would you design, decisively Redis, he said at Redis advantage, thread pool,
3.Redis and Memcache difference,
Several parameters 4. thread pool, which refused strategy (this problem by heart, even gave his colleagues trained),
5.mysql slow queries, how would you optimize,
6. The index is what principle, can not describe,
7. If id is now 192, you talk about the B + Tree of the search process,
8. There is a reading and writing little scenes, how you design (answer Canel monitor binlog, read from the Redis. But consistency is not the interviewer questioned. Then he said separate read and write, then I question his isolated and can not read and write ensure consistency, he said that this delay is very small [ha ha])
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synchronized lock implementation principle:
synchronized is achieved by a pair of monitorenter / monitorexit instruction, monitor objects are basically synchronized unit.
Before Java 6, is implemented entirely on internal monitor operating system mutex, because of the need to switch the user mode kernel mode, a synchronous operation is undifferentiated heavyweight operation, performance is very low.
But when Java 6, Java virtual machine conducted a drastically improved, providing three different monitor implementation,
That is often said that three different locks: Lock biased (Biased Locking), lightweight and heavyweight lock lock, which greatly improved its performance.
synchronized lock escalation works:
In the object header locks the object which has a threadid field, at the time of the first visit threadid is empty, jvm allowed to hold biased locking and threadid set to its thread id,
Again the time of entry will first determine whether the threadid consistent with its thread id, if consistent, you can directly use this object, and if not, then upgrade biased locking is a lightweight lock,
To get through the spin cycle of a certain number of lock, after performing a certain number of times, if you do not normally get to the object you want to use, then it will upgrade the lock locks from lightweight to heavyweight, this process constitutes a synchronized lock upgrade.
Lock escalation purposes:
Lock escalation is a lock to bring order to reduce the consumption of performance. After optimization of Java 6 implementation of synchronized using a biased locking upgraded to lightweight to heavyweight and then upgrade lock lock manner, thus reducing the lock performance brought consumption.
Worst Resume:
