Epsilon Lead Developer Interview Questions, Process, and Tips

Q1. Basic JavaScript and React.js questions
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Q2. Questions on functions, hooks and DOM
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Q3. Questions on SSR
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Q4. Questions on strings and arrays
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Api related questions

Q1. Asked two array and string dsa questions of medium-hard level
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Held on interview bit. 3 ques were asked. Questions were from range query and DP.

Q1. 1 Hard DSA question. Given a sequence of positive numbers, make it a non-decreasing sequence. Operation allowed: adjacent elements can be added to form a single element. What is the minimum no of operatio...read more
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It will be around 3 hours and 2 questions of leetcode hard difficulty will be asked in the interview and 1 question is of codeforces 2400+ difficulty question.

Q1. 1-2 DSA medium-hard difficulty question will be asked.
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Q2. CS fundamentals in depth had been asked in the ending of the interview.
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Q1. System Design problem was asked.
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Q1. This is a cultural fit round. Common HR question was asked.
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Round duration - 75 minutes
Round difficulty - Easy

This round was conducted in Hackerrank portal for a total duration of 75 minutes and was divided into 4 sections.

1st Section : Aptitude Section : 14 questions , 28 minutes
2nd Section : Technical Section : 12 questions , 17 minutes
3rd Section :1 coding Questions : 20 minutes+30 minutes

This Round was Conducted on Hackerrank (Webcam Enabled).

Q1. Given a problem statement and a piece of code, how would you find and correct the bug in the code?
Ans. 
To find and correct a bug in code, analyze problem statement, review code, use debugging tools, and test different scenarios.
• Understand the problem statement and expected output

• Review the code for syntax errors, logical errors, and potential bugs

• Use debugging tools like breakpoints, print statements, and IDE debuggers

• Test the code with different inputs and edge cases to identify the bug

• Make necessary corrections and re
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Q2. 
Nodes at Distance K from Target Node in Binary Tree
Given a Binary Tree of distinct integers and two integers, target and K, return a list of values of all nodes located at a distance K from the target no...read more
Ans. 
Find nodes at distance K from target node in a Binary Tree.
• Use BFS to traverse the tree and keep track of the distance of each node from the target node.

• Maintain a set to keep track of visited nodes to avoid revisiting them.

• Return the values of nodes at distance K from the target node.
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Round duration - 90 minutes
Round difficulty - Medium

I was shared a link of Google Meet and the Google Docs was shared where there was 1 coding problem to be coded there and then the code was run on an IDE to check the sample tests.
Then the interview was followed by a lot of Operating System and Computer System Architecture Questions.
There were 2 Interviewers and both were helpful.
The timing was from 2:30 PM to 4:00 PM

Q1. 
Subarray Challenge: Largest Equal 0s and 1s
Determine the length of the largest subarray within a given array of 0s and 1s, such that the subarray contains an equal number of 0s and 1s.
Input:
Input beg...read more
Ans. 
Find the length of the largest subarray with equal number of 0s and 1s in a given array.
• Iterate through the array and maintain a count of 0s and 1s encountered so far.

• Store the count difference in a hashmap with the index as key.

• If the same count difference is encountered again, the subarray between the two indices has equal 0s and 1s.

• Return the length of the longest subarray found.
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Round duration - 45 minutes
Round difficulty - Easy

The round was held on Google Meet with HR from 2:30 PM to 3:15 PM.
The HR was friendly and asked the basic questions.

Round duration - 90 Minutes
Round difficulty - Hard

The test was at 6 pm with cam on and in fullscreen mode.

Q1. 
Interleaving Two Strings Problem Statement
You are given three strings 'A', 'B', and 'C'. Determine if 'C' is formed by interleaving 'A' and 'B'.
String 'C' is an interleaving of 'A' and 'B' if the lengt...read more
Ans. 
The problem involves determining if a string 'C' is formed by interleaving two given strings 'A' and 'B'.
• Check if the length of 'C' is equal to the sum of the lengths of 'A' and 'B'.

• Verify if all characters of 'A' and 'B' exist in 'C' while maintaining their order.

• Return 'True' if 'C' is an interleaving of 'A' and 'B', otherwise return 'False'.
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Q2. 
Construct Binary Tree from Inorder and Postorder Traversal
Given two lists representing the inorder and postorder traversal of a binary tree of integer type with 'N' nodes, construct the binary tree and r...read more
Ans. 
Construct a binary tree from inorder and postorder traversal lists and return its root.
• Create a map to store the indices of elements in the inorder traversal list for quick access during tree construction.

• Use the postorder list to determine the root of the tree and recursively build left and right subtrees.

• Construct the tree by recursively dividing the inorder list based on the root index in postorder list.

• Return the r...read more
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Round duration - 45 Minutes
Round difficulty - Easy

At 10:00 AM. Interviewer was very friendly and young but his cam was off.

Q1. 
Find Paths in Binary Tree
Kevin has sketched a series of integers, forming a diagram that represents a binary tree. Challenged by a friend, Kevin needs to find all paths from the root to the leaf where th...read more
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Round duration - 45 Minutes
Round difficulty - Easy

It was held at 4 p.m. The interviewer was senior compared to the one in the previous round. Also, his cam was also on, but he wasn't speaking much and neither giving any expressions.

Q1. 
Boxes of Power Problem Statement
Given a set of boxes represented by an array gainPower, where each box has a certain power value, along with an initial power value 'power', your task is to maximize the t...read more
Ans. 
Maximize total score by selecting boxes optimally based on power values and operations.
• Iterate through the boxes and perform operations based on power values and current score

• Keep track of power, score, and selected boxes to maximize total score

• Example: For input [3, 50, [20, 30, 40]], select boxes with power 20 and 30 to get a score of 2
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Q1. Tell me about yourself in brief ?
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Q2. Was your the experience with previous companies ?
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