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There are only questions, but no answers.

  • How to implement an efficient one-way list reverse output?
  • Given that SQRT (2) is approximately equal to 1.414, we require that SQRT (2) be accurate to 10 decimal places without using the math library.
  • Given a binary search tree (BST), find the KTH smallest node in the tree.
  • LRU Caching Mechanism Design and implement an LRU (least recently used) cache data structure that should support the following operations: GET and PUT. Get (key) – Gets the value of the key if it exists in the cache (always positive), otherwise -1 is returned. Put (key,value) – If key does not exist, set or insert value. When the cache reaches its capacity, it should invalidate the least recently used items before inserting new ones.
  • What is true about the difference between epoll and SELECT? (pops)

A. Epoll and SELECT are I/O multiplexing technologies that can monitor the status of multiple I/O events at the same time.

B. Epoll is more efficient than SELECT because of the I/O event notification mechanism supported by the operating system, while SELECT is based on polling.

C. Epoll supports two modes: horizontal trigger and edge trigger.

D. Select Supports parallel I/ OS. The I/ OS are small and cannot be modified.

  • Which trigger method is more efficient for epoll with high concurrent access? What are some things to look out for when using edge triggers?
  • From innoDB index structure analysis, why index key length can not be too long?
  • How can MySQL data be restored to any point in time?
  • NFS and SMB are the two most common Network Attached Storage (NAS) protocols. When a file system is shared to multiple hosts using NFS and SMB protocols, which statements are incorrect? (Multiple options)

A. It is impossible to share A file system to multiple hosts using NFS and SMB.

B. A file or directory created by a user of host A using the NFS protocol cannot be deleted by a user of host B using the SMB protocol.

C. In the same directory, host A can view file file. TXT using NFS, and host B can view file file. TXT using SMB.

D. Host A uses NFS and host B uses SMB to cache data on the host to improve file access performance.

  • Type ping IP and press Enter. What happens before the packet is sent?
  • Please explain why the weibo system crashes when Lu Han announces his relationship, and how to solve it?
  • A batch of mail needs to be sent to subscribers, and there is a cluster (the number of nodes in the cluster is variable, and the capacity will be dynamically expanded and shrunk) to take charge of the specific mail sending task. How to make the system complete the mail sending as soon as possible? Please specify the technical solution!
  • You need to obtain the observation data of a number of meteorological observation stations and store them in Hive. But the weather service only provides API queries, which can only be queried at a single observation point at a time. What if we could quickly and easily get all the data from all the observation points?
  • How to add two amounts of data (up to two decimal places)?
  • Some fundamental open questions about parallel computing.

◼ how to define and calculate, please explain the difference and implementation of distributed memory to shared memory pattern line programming respectively (example code)?

◼ Can N processors sum M variables using MPI and OpenMP respectively?

◼ What permissions are used by SIMD instructions in loops? What are the means of vectorization optimization?

◼ please use Amdahl’s law to explain what is parallel efficiency and the scalability of parallel algorithms? Describe scalability performance indicators and limitations. Finally, describe the limitations of shared memory on a shared memory computer. How does OpenMP implement a shared memory programming environment? What is the difference between MPI blocking and non-blocking reads and writes?

  • Please calculate how much TOPS is equal to the computing power of XILINX COMPANY VU9P chip, and give the calculation process and formula.
  • How many simple MOV instructions can a modern processor execute per second? What are the main influencing factors?
  • Please analyze the relationship between MaxCompute product and distributed technology and the current market status and development trend of big data computing platform products.
  • How to understand the metadata management in the big data platform, what is the metadata collection management system, and what kind of impact it will have on the big data application.
  • You understand the technical system differences, development trends and technical bottlenecks of big data platforms such as Alibaba and Youshang, and give an overview in storage and computing.
  • In the cloud computing big data processing scenario, thousands of tasks run every day, and each task requires I/O reads and writes. For better service, a storage system often ensures that high-priority tasks are executed first. How to ensure priority and fairness when multiple jobs or users access the storage system?
  • Maximum frequency stack.
  • FreqStack, a class that simulates the operation of stack-like data structures. FreqStack has two functions: push(int x), which pushes the integer x onto the stack. Pop (), which removes and returns the most frequent element on the stack. If more than one element is most frequently used, the element closest to the top of the stack is removed and returned. ◼ example: push [5,7,5,7,4,5] pop() -> returns 5 because 5 is the most frequent occurrence. The stack becomes [5,7,5,7,4]. Pop () -> returns 7, because both 5 and 7 are the most frequent, but 7 is closest to the top of the stack. The stack becomes [5,7,5,4]. Pop () -> return 5. The stack becomes [5,7,4]. Pop () -> return 4. The stack becomes [5,7].
  • Given a linked list, delete the NTH last node of the list and return the first node of the list.

◼ example: Given a linked list: 1->2->3->4->5, and n = 2. When the penultimate node is deleted, the linked list becomes 1->2->3->5. Note: the given n is guaranteed to be valid. Requirement: Only one traversal of the linked list is allowed.

  • If you could design a universal system that supported second backups and recovery of all kinds of databases, what would you do?
  • If you were asked to design a data flow and processing system that supports the real-time flow of data between databases, NOSQL, and big data, what would you consider? How to design?
  • Given an array of integers and an integer, returns the indexes of two arrays whose sum equals the specified integer. The optimal algorithm is needed to analyze the spatial and temporal complexity of the algorithm
  • If you were given a new product, what would you do to ensure its quality?
  • Please evaluate the results of the program?
  • How do you test a bike?
  • How do I determine if two linked lists intersect?

Meituan article

  • Java virtual machine memory model
  • Memory overflow usually occurs in this area? Will persistent generation cause memory overflow?
  • How about a framework for dynamically loading classes?
  • How are dynamic proxies generally implemented? What are the application scenarios of dynamic proxy?
  • Do stacks overlap? What exceptions are thrown when stacks overlap? Where does the JVM set the stack size? What are the parameters set?
  • Have you used commands to check the state of the JVM?
  • JVM garbage collection mechanism?
  • Java class loading mechanism? How to implement a custom class loader? The difference between findClass and loadClass?
  • What’s the difference between String, StringBuffer, StringBuilder? What are the corresponding application scenarios?
  • How do you implement immutable classes?
  • Shallow copy and deep copy? How to implement deep copy?
  • What is the difference between HashMap, HashTable, ConcurrentHashMap?
  • CAS is some kind of synchronization mechanism, right?
  • What are the components of NIO?
  • A brief introduction to Reflection in Java? Does reflection have application scenarios in some places?
  • Spring’s process for loading beans?
  • Java thread pools? What are the parameters of the thread pool constructor? KeepAliveTime explain?
  • One interface calls five other interfaces, each of which returns data to the calling interface, which merges the data and returns it to the upper layer. What kind of category might such a scenario use and outsource? How would you implement such a business scenario?
  • What’s the difference between CountDownLatch and CyclicBarrier?
  • What are the ways to screw lock? What’s the difference between synchronization and locking?
  • What does the volatile keyword do? Why use AtomicLong and not Long? How is AtomicLong’s transformation implemented?
  • What are the storage engines of mysql?
  • What are the starting points for SQL optimization? What does the left-most alignment principle for composite indexes mean?
  • How does SpringMVC process requests?
  • How do Spring transactions work? Transaction rollback? Custom exceptions?
  • Dirty read? Phantom read?
  • How does TCP wave four times? TIME_WAIT Why at least double MSL time?
  • What’s the difference between get and POST requests?
  • Cookie and session requests?
  • What open source middleware do you know? The cache? The message? Distributed framework?
  • Use some design patterns? Implementation of singleton pattern?
  • Database transaction realization principle, operation process, how to achieve the independence between things and other issues
  • Database dirty read, unreal read, unrepeatable read appear reason principle, solution
  • Isolation level of the database, MVCC
  • Optimistic lock, pessimistic lock, mutex lock, read and write lock principle implementation and difference
  • The life cycle of a thread
  • Principles and applications of the consistent Hash algorithm
  • The principle of CAP
  • The CAS operation
  • Distributed RAFT algorithm

Jingdong paper

  • General SQL injection how to find links from binary sqlMap how to test injection points.
  • How does Masscan scan ports and why so fast? Please contrast.
  • You’ve written widgets, and what changes you’ve made to the tools you’ve used.
  • How to improve the scanning speed written in Python, talk about GIL lock understanding.
  • You think the breakthrough you made made a big difference.
  • What are the common network extensions?
  • Have you ever played hardware security, how much research?
  • Anti-crawler, if it is how you do anti-crawler, how to bypass anti-crawler measures. Headless browser detected, how to bypass?
  • Nmap Scan How to scan. Packet and protocol, handshake and no-handshake, these protocol handshakes, some kind of no-handshake. How do I detect whether the port is open without directly contacting the target server?
  • If you want to solve the problem of scanning {k1: v1, k2: v2, k3: v3}, make sure that the specific value appears in K1 v1, k2 v2, and K3, v3 at the same time. How do you do that?
  • What is the principle of XSS and how to implement an XSS platform similar to BEEF. Since this is implemented, how to solve the cross-domain problem?
  • IP frequency limit, IP credibility model?
  • What is the SCTP protocol? How can YOU optimize your network using SCTP?

Redis is often asked questions in interviews

  1. What are the benefits of using Redis?
  2. What advantages does Redis have over memcached?
  3. Redis Common performance problems and solutions
  4. MySQL has 2000W data, redis only 20W data, how to ensure that the data in Redis is hot data?
  5. Four types of ZooKeeper ZNodes
  6. What are the differences between Memcache and Redis?
  7. What are the common performance issues with Redis? How to solve it?
  8. Redis is the most suitable scenario
  9. How about Redis synchronization?
  10. Have you used Redis clustering? How does clustering work?

Interview often ask MySQL questions

  1. Primary key superkey candidate what is a foreign key
  2. Four features of database transactions and their implications
  3. What does a view do? Can a view change?
  4. Differences between DROP, DELETE, and TRUNCate
  5. How indexes work and their types
  6. Type of connection
  7. Database paradigm
  8. The idea of database optimization
  9. The difference between stored procedures and triggers
  10. Explain the left join and right join.md of SQL

MongoDB is often asked interview questions

  1. What is MongoDB?
  2. What language is MongoDB written in?
  3. What are the advantages of MongoDB?
  4. What is a database
  5. What is a set
  6. What is a document
  7. Comparison of MongoDB and relational database terms
  8. What is “Mongod”?
  9. What are the “Mongod” parameters?
  10. What is “Mongo”?
  11. Which MongoDB command can switch databases?
  12. What is a non-relational database?
  13. What are the types of non-relational databases?
  14. Why MOngoDB?
  15. In what scenarios is MongoDB used?
  16. What do namespaces in MongoDB mean
  17. Which languages support MongoDB?
  18. How do I create a new database in MongoDB?
  19. How do I view a list of databases in MongoDB?
  20. What is sharding in MongoDB?
  21. How do I view connections using MongoDB?
  22. What is replication?
  23. How do I insert a document into a collection in MongoDB?
  24. How do I remove a database in MongoDB?
  25. How do YOU create a collection in MongoDB?
  26. How do I view a created collection in MongoDB?
  27. How do I delete a collection in MongoDB?
  28. Why use profilers in MongoDB?
  29. Does MongoDB support primary and foreign key relationships?
  30. What data types does MongoDB support?
  31. Why Code data type in MongoDB?
  32. Why use Regular Expression in MongoDB?
  33. Why is the Object ID data type used in MongoDB?
  34. How do I insert a document into a collection?
  35. What are the components of the ObjectID?
  36. What is an index in MongoDb?
  37. How do I add indexes?
  38. What are the alternatives to MongoDB?
  39. How do I query documents in a collection?
  40. In what way can the output be formatted?
  41. How do I use AND OR OR conditional loops to query documents in a collection?
  42. How do I update data in MongoDB?
  43. How do I delete a document?
  44. How do you sort in MongoDB?
  45. What is aggregation?
  46. What is a replica set in MongoDB
  47. Mongodb storage features and internal principles

Zookeeper is a common interview question

  1. What is Zookeeper?
  2. What does ZooKeeper offer?
  3. Zookeeper file system
  4. Four types of ZooKeeper ZNodes
  5. Zookeeper notification mechanism
  6. What are the application scenarios of ZooKeeper?
  7. Zk naming service.
  8. K configuration management service.
  9. Cluster management for ZK.
  10. Zk distributed lock
  11. Zk queue management
  12. Zk data replication
  13. Working principle of ZAB in ZK
  14. How does ZK keep things in the same order
  15. Server status in the ZK cluster
  16. How does ZK elect its Leader
  17. Zookeeper synchronization process
  18. Distributed notification and coordination
  19. Zk session mechanism

Above is the github big guy spent a year to sort out the interview questions about Ali, JINGdong, Meituan and other big factories, the above questions only have no answers, the topic is just for reference, I hope to interview readers looking for a job or ready to change jobs of readers friends help.

However, after nearly a year of sorting, xiaobian here has collected part of the interview related information, the content may not be completely consistent with the appeal, but the information also includes a lot of knowledge points, These include basics, Java collections, JVMS, multi-threaded concurrency, Spring principles, microservices, Netty and RPC, Kafka, diaries, design patterns, Java algorithms, databases, Zookeeper, distributed caching, data structures, and more.

The following interview answers are all free to share, have the need of the program ape (yuan) canPlease forward it and add assistant VX: Yunduoa2019 after following it or scan the qr code below and follow the guidance of the assistant to obtain it by yourself​

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