HashedIn by Deloitte Interview Questions, Process, and Tips

Round duration - 85 Minutes
Round difficulty - Medium

3 Coding questions were asked . 1 - easy , 2- medium , 3 - medium -hard .

Q1. 
Convert Binary Tree to Mirror Tree
Convert a given binary tree into its mirror tree, where the left and right children of all non-leaf nodes are interchanged.
Input:
An integer ‘T’ denoting the number o...read more
Ans. 
Convert a binary tree into its mirror tree by interchanging left and right children of non-leaf nodes.
• Traverse the tree in postorder fashion and swap the left and right children of each node.

• Recursively call the function on the left and right subtrees.

• Modify the tree in place without creating a new tree.

• Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the output should be 7 4 2 1 6 3 5.
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Q2. 
Binary Palindrome Check
Given an integer N, determine whether its binary representation is a palindrome.
Input:
The first line contains an integer 'T' representing the number of test cases. 
The next 'T'...read more
Ans. 
Check if the binary representation of an integer is a palindrome.
• Convert the integer to binary representation

• Check if the binary representation is a palindrome by comparing it with its reverse

• Return true if it is a palindrome, false otherwise
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Q3. 
Ways To Make Coin Change
Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make...read more
Ans. 
The task is to find the total number of ways to make change for a specified value using given denominations.
• Create a dynamic programming table to store the number of ways to make change for each value up to the target value.

• Iterate through each denomination and update the table accordingly.

• The final answer will be the value in the table at the target value.

• Consider edge cases such as when the target value is 0 or when ...read more
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Round duration - 45 Minutes
Round difficulty - Easy

This was the combo of coding the subject theory round . I was several DSA problems . I was able to give optimal solutions for them .Also the questions related to OS , CN and DBMS were asked.

Q1. 
Palindrome Permutation - Problem Statement
Determine if a permutation of a given string S can form a palindrome.
Example:
Input:
string S = "aab"
Output:
"True"
Explanation:
The permutation "aba" o...read more
Ans. 
Check if a permutation of a string can form a palindrome.
• Create a frequency map of characters in the string.

• Count the number of characters with odd frequencies.

• If there is at most one character with an odd frequency, the string can form a palindrome.
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Round duration - 60 Minutes
Round difficulty - Easy

Main focus was on design .

Q1. Design a Movie Player system
Ans. 
Design a Movie Player system
• 1. Create a user interface for selecting and playing movies

• 2. Implement features like play, pause, stop, rewind, fast forward

• 3. Include options for adjusting volume and screen brightness

• 4. Support different video formats like MP4, AVI, MKV

• 5. Allow users to create playlists and save favorite movies
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First round is a basic DS-Algo Round. It was a pen & paper interview. 2 interviewers asked me to write code for some problems such as:
1. You have an unsorted array of 0s and 1s, find the first 1. Different approaches for it.
2. What is setTimeOut in Node.JS?
3. How can you use 2 stacks as an array.
4. You have 2 sorted arrays. Merge them into a single array.

Q1. What are OS processes?
Ans. 
OS processes are instances of a program that are being executed by the operating system.
• Processes are managed by the operating system's scheduler.

• Each process has its own memory space and system resources.

• Processes can communicate with each other through inter-process communication (IPC).

• Examples of processes include web browsers, media players, and text editors.
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Q2. What are threads? What is the purpose?
Ans. 
Threads are lightweight processes that enable multitasking within a single process.
• Threads allow multiple tasks to be executed concurrently within a single process.

• They share the same memory space and resources of the parent process.

• Threads can improve performance by utilizing available CPU resources more efficiently.

• Examples include web servers handling multiple requests simultaneously and video games rendering graphi
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Q3. Why should one use Node.JS?
Ans. 
Node.js is a powerful and efficient server-side JavaScript runtime environment.
• Node.js is fast and scalable, making it ideal for building real-time applications.

• It uses an event-driven, non-blocking I/O model, which makes it lightweight and efficient.

• Node.js has a large and active community, with many useful libraries and modules available.

• It allows for easy sharing of code between the server and client, using JavaScri...read more
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Q4. What is difference between Python and Node.JS?
Ans. 
Python is a general-purpose language while Node.JS is a JavaScript runtime environment.
• Python is used for web development, data analysis, artificial intelligence, and scientific computing.

• Node.JS is used for building scalable network applications and real-time web applications.

• Python is slower than Node.JS in terms of performance.

• Python has a larger standard library than Node.JS.

• Python is easier to learn and has a simp
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Q5. What is the difference between SQL and NoSQL?
Ans. 
SQL is a relational database management system while NoSQL is a non-relational database management system.
• SQL databases are table-based while NoSQL databases are document-based, key-value pairs, graph databases, or column-based.

• SQL databases are structured while NoSQL databases are unstructured.

• SQL databases use SQL (Structured Query Language) for querying and managing data while NoSQL databases use different query lan...read more
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Q6. High Level Design for a Reddit type application
Ans. 
A Reddit-like application for sharing and discussing content
• User authentication and authorization

• Post creation and voting system

• Commenting system

• Subreddit creation and management

• Search functionality

• Real-time updates using websockets
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Q7. What are CORS? How to handle them?
Ans. 
CORS stands for Cross-Origin Resource Sharing. It is a security feature implemented in web browsers to restrict web pages from making requests to a different domain.
• CORS is used to prevent malicious websites from accessing sensitive data from other websites.

• To handle CORS, the server needs to include specific headers in the response to allow the browser to make requests from a different domain.

• The most common header us...read more
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Q8. What is CRFS? The experience around working with it.
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Q1. The final round was with a Senior Manager and he asked about my previous work experience.
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Q2. Low Level Design for Authentication
Ans. 
Low level design for authentication
• Define authentication requirements

• Choose appropriate authentication mechanism

• Design authentication flow

• Implement secure storage of credentials

• Consider multi-factor authentication

• Include error handling and logging
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Q3. Have you managed a team before
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Q4. Architecture Design for an e2e system that takes input from user to the response shown to the user
Ans. 
An e2e system architecture design for user input to response output
• Identify user requirements and define system goals

• Choose appropriate technologies and frameworks

• Design system components and their interactions

• Ensure scalability, reliability, and security

• Test and validate the system before deployment
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Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Merge K Sorted Arrays Problem Statement
Given 'K' different arrays that are individually sorted in ascending order, merge all these arrays into a single array that is also sorted in ascending order.
Inpu...read more
Ans. 
Merge K sorted arrays into a single sorted array.
• Create a min-heap to store the first element of each array along with the array index.

• Pop the smallest element from the heap and add it to the result array.

• If the array from which the element was popped has more elements, add the next element to the heap.

• Repeat until all elements are merged into a single sorted array.
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Round duration - 60 Minutes
Round difficulty - Easy