Alation Interview Questions and Answers

Round duration - 180 minutes
Round difficulty - Hard

The test link had 3 days expiry so I could attempt test anytime. It was conducted on doselect.com

Q1. 
Equilibrium Indices in a Sequence
You are given an array/list named 'SEQUENCE', which consists of 'N' integers. The task is to identify all equilibrium indices in this sequence.
Explanation:
An equilibr...read more
Ans. 
The task is to find the equilibrium indices of a given sequence, where the sum of elements at lower indices is equal to the sum of elements at higher indices.
• Iterate through the sequence and calculate the total sum of all elements

• Initialize a left sum and right sum as 0

• For each index, update the left sum and right sum and check if they are equal

• If they are equal, add the index to the equilibrium indices

• Return the equil
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Round duration - 60 minutes
Round difficulty - Medium

Video interview round wherein I was asked to wrote code for the problem statements given by the interviewer. The problems were mainly focused on advanced JS concepts like asynchonous progamming, timers, closures, and data structure problems around arrays, sets, linked list etc.

Q1. 
Rearrange Linked List Problem Statement
Given a singly linked list in the form 'L1' -> 'L2' -> 'L3' -> ... 'Ln', your task is to rearrange the nodes to the form 'L1' -> 'Ln' -> 'L2' -> '...read more
Ans. 
The task is to rearrange the nodes of a singly linked list in a specific order without altering the data of the nodes.
• Iterate through the linked list to find the middle node using the slow and fast pointer technique.

• Reverse the second half of the linked list.

• Merge the first and reversed second half of the linked list alternatively to get the desired order.
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Round duration - 30 minutes
Round difficulty - Easy

This was the last round with HR wherein they judged cultural fit and there was discussion on things like my expectations v/s their expectations etc.

Round duration - 30 minutes
Round difficulty - Easy

This round mainly consisted of some questions on advanced JS topics like Execution Context, Callback queue, Micro task queue, Promises, etc.

Round duration - 60 minutes
Round difficulty - Medium

This round was more technical compared to the previous one. The interviewer was a senior developer. If questions were not answered, answers would be given/explained.

Q1. What are some aggregate operators in MongoDB?
Ans. 
Aggregate operators in MongoDB are used for data aggregation and manipulation.
• Some aggregate operators in MongoDB include $sum, $avg, $min, $max, $push, $addToSet, $first, $last, $project, $match, $group, $sort, $limit, $skip.

• Example: db.collection.aggregate([{$group: {_id: '$field', total: {$sum: '$value'}}}])
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Round duration - 30 minutes
Round difficulty - Easy

This round was mainly to assess my experience level, roles, and responsibilities from my previous company. Salary negotiations also happened here.

Q1. Write a Prime number function using C
Ans. 
A function in C to check if a number is prime or not
• Create a function that takes an integer as input

• Check if the input number is divisible by any number from 2 to its square root

• If it is not divisible by any number, return true (prime), else return false (not prime)
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Q2. Write some basic codes for Manipulation in array
Ans. 
Basic codes for array manipulation including sorting, searching, and filtering.
• Use built-in functions like sort() for sorting arrays.

• Implement algorithms like binary search for searching in arrays.

• Utilize filter() method for filtering arrays based on specific criteria.
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Always be confident and make an effort to listen before you speak.

Q1. Tell me about yourself.
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