HackerRank Senior Backend Engineer Interview Questions and Answers

1 hr test on HackerEarth platform, DSA questions

Q1. Question on anagram whether we can form with given strings
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Q2. Play random song from list without repetition
Ans. 
Use Fisher-Yates shuffle algorithm to play songs randomly without repetition.
• Create an array of songs

• Use Fisher-Yates shuffle algorithm to shuffle the array

• Play the first song in the shuffled array

• Remove the first song from the array

• Repeat steps 3-4 until all songs have been played
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Q3. Reverse the linked list
Ans. 
Reverse a linked list
• Iterate through the linked list and change the direction of the pointers

• Keep track of the previous, current, and next nodes

• Set the head of the linked list to the last node after reversing
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Q4. Range sum with the queries
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Q5. Hashing on 2d matrix counting max 1
Ans. 
Hashing algorithm to count maximum number of 1s in a 2D matrix.
• Create a hash table to store the count of 1s in each row.

• Traverse through each row and update the count in the hash table.

• Find the row with the maximum count of 1s in the hash table.

• Return the count of 1s in that row.
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Q6. React interviews hooks
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It was a Basic Aptitude Test

We were asked to do Sorting, SQL queries (join)

Q1. Can you tell me about yourself?
Ans. 
I am a passionate software engineer with 5 years of experience in developing web applications using various technologies.
• 5 years of experience in software development

• Proficient in developing web applications

• Skilled in using various technologies such as Java, JavaScript, and SQL
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Q1. Design a data structure that can take a number with infinite digits and support operation like addition
Ans. Create a linked list of number where each node is a digit of a number
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Q2. Explain in-depth of the projects you did
Ans. Explain project in details with all complexities
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Q1. Design a system that reads content of a file and show it in a webpage as the file gets update the webpage should also get updated in realtime
Ans. 
Design a system to display real-time updates of a file's content on a webpage.
• Use a server-side programming language like Node.js to read the file content.

• Implement a WebSocket connection between the server and the webpage for real-time updates.

• Whenever the file is updated, send the updated content to the webpage using the WebSocket connection.

• Update the webpage dynamically using JavaScript to display the new content.
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Q1. Engineering Manager round - Explain the projects you did in detail
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Q1. Director round - Explain the projects in details
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Q1. Explain projects in high level
Ans. 
I have worked on various projects involving software development and implementation.
• Developed a web application for a retail company to manage inventory and sales.

• Implemented a mobile app for a healthcare organization to track patient data and appointments.

• Created a data analysis tool for a financial institution to analyze market trends and make investment decisions.
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Q2. Explain your strong points
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Q3. Explain your entire background
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Q1. Explain what happens when we click on a URL
Ans. 
When we click on a URL, the browser sends a request to the server, which responds with the requested webpage.
• Clicking on a URL triggers the browser to send an HTTP request to the server.

• The server receives the request and processes it.

• The server then sends back a response containing the requested webpage.

• The browser receives the response and renders the webpage for the user to view.
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Q2. When a number is represented in LinkedList, how do we add 2 numbers
Ans. 
To add two numbers represented as linked lists, iterate through both lists simultaneously, adding corresponding digits and carrying over the carry value.
• Create a new linked list to store the result.

• Initialize a carry variable to 0.

• Iterate through both linked lists simultaneously, adding the corresponding digits and the carry value.

• If the sum of the digits is greater than 9, update the carry value and store the remainde...read more
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Q1. Machine coding round
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Q2. Chat app using sockets
Ans. 
A chat app using sockets allows real-time communication between users.
• Use a socket library or framework to handle the communication.

• Implement a server that listens for incoming connections and manages the chat rooms.

• Establish a socket connection between the server and clients for sending and receiving messages.

• Handle message encryption and decryption for secure communication.

• Implement features like user authentication,...read more
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Q1. Project Discussions
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Q1. Why am i leaving my old org etc
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Code the LRU cache on hacker rank

Q1. Code the tail -f logger
Ans. 
Implement a tail -f logger in code
• Use a file pointer to open the log file

• Read the file line by line and print new lines as they are added

• Use a loop to continuously check for new lines in the file
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A working software coding problem. Build client-server. Make sure your IDE is ready

Q1. Difference between async, concurrency and parallelism
Ans. 
Async is non-blocking, concurrency is managing multiple tasks at the same time, parallelism is executing multiple tasks simultaneously.
• Async allows non-blocking execution of code, enabling other tasks to run while waiting for I/O operations.

• Concurrency involves managing multiple tasks at the same time, but not necessarily simultaneously.

• Parallelism is executing multiple tasks simultaneously, utilizing multiple CPU core...read more
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Q2. Journey of request
Ans. 
The journey of a request refers to the process of a request being made, processed, and fulfilled by a system.
• Request initiation by a user or system

• Routing of the request to the appropriate service or endpoint

• Processing of the request by the service

• Response generation and delivery back to the user
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Q1. What are your strengths
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Q2. What irritates you
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