Mantra Labs Front end Developer Interview Questions and Answers

An online open assisment is given and it has around 50 MCQs that need to be done in 50 mins

An assignmnet is given that need to be done in 7 days

Round duration - 180 Minutes
Round difficulty - Medium

General Questions Like - Introduction & How all the round have gone so far

Round duration - 90 Minutes
Round difficulty - Medium

One-to-One Interview based on DSA and Front-End Technologies including HTML, CSS & JS.

Q1. 
Remove Duplicates Problem Statement
You are given an array of integers. The task is to remove all duplicate elements and return the array while maintaining the order in which the elements were provided.
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Ans. 
Remove duplicates from an array of integers while maintaining order.
• Iterate through the array and add elements to a new array if they are not already present

• Use a hash set to keep track of unique elements

• Return the new array with unique elements in the same order as the original array
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Round duration - 90 Minutes
Round difficulty - Hard

One-to-One Interview based on Front-End Technologies including HTML, CSS & JS.

In the last 10-20 minutes, some behavioral questions were asked:
1 How would you grade yourself in the interview so far?
2. You are present in a team and you have to convince your team members & client that your approach is better than the other team members.
3. You are the team leader & you have to point out & convey the negative points of a member of your team without getting him/her hurt.
- At last, they asked me if I have questions for them( I asked 2 questions ) & then the interview ended.

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 top element from the heap, add it to the result array, and push the next element from the same array back to the heap.

• Repeat the process until all elements are processed.

• Time complexity: O(N log K) where N is the total number of elements and K is the number of arrays.
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Round duration - 90 Minutes
Round difficulty - Easy

You are given three ds coding questions which you have to solve within 90 mins.
The questions are easy to medium level for this round

Q1. 
Non-Decreasing Array Problem Statement
Given an integer array ARR of size N, determine if it can be transformed into a non-decreasing array by modifying at most one element.
An array is defined as non-de...read more
Ans. 
The solution checks if an integer array can become non-decreasing by modifying at most one element.
• Iterate through the array and check if there are more than one decreasing pairs of elements.

• If there are more than one decreasing pairs, return false.

• If there is only one decreasing pair, check if modifying one of the elements can make the array non-decreasing.

• If modifying the element at index i-1 or i can make the array ...read more
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Q2. 
Sort Linked List Based on Actual Values
You are given a Singly Linked List of integers that is initially sorted according to the absolute values of its elements. Your task is to sort this Linked List base...read more
Ans. 
The task is to sort a singly linked list based on actual values instead of absolute values.
• Traverse the linked list and store the values in an array

• Sort the array using any sorting algorithm

• Create a new linked list using the sorted array

• Return the new linked list
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Q3. 
Diameter of a Binary Tree Problem Statement
Given a binary tree, return the length of its diameter. The diameter of a binary tree is defined as the length of the longest path between any two nodes in the ...read more
Ans. 
The diameter of a binary tree is the length of the longest path between any two end nodes in the tree.
• The diameter of a binary tree can be calculated by finding the maximum of the following three values: 1) the diameter of the left subtree, 2) the diameter of the right subtree, and 3) the longest path that passes through the root node.

• To find the diameter of a binary tree, we can use a recursive approach. We calculate ...read more
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Round duration - N/A
Round difficulty - Medium

Round duration - 120 Minutes
Round difficulty - Hard

This round focus on advanced Js concepts and the tech stack I used in my projects.

Q1. 
Find Unique Element in Array
You have been provided an integer array/list ARR of size N. Here, N is equivalent to 2M + 1 where each test case has M numbers appearing twice and one number appearing exactly...read more
Ans. 
The task is to find the unique number in an array where all other numbers occur twice.
• The array size is given by N = 2M + 1, where M is the number of elements occurring twice.

• Loop through the array and use a hashmap to count the occurrences of each number.

• Return the number with a count of 1, as it is the unique number.
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Round duration - 60 Minutes
Round difficulty - Easy

It was a late night round as i have already had the previous 3 rounds at the same day. The HR asked about my experience regarding the previous rounds and also some situation based questions.

- They use their own platform for interviews, and assessments.
- There were html, css, js based questions in the coding round.
- Some questions were theoretical too.
- They tested nearly all major parts of js including let, const, arrays, promise, async, await, events, lexical scope, etc.

Q1. It was an online machine coding round, where you have to build something they ask in 1hr using html, css, js (vanilla).
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Q1. Focused on html, css, and js (basic)
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Q1. Focus majorly on JS some quick demonstration, advanced concepts like closures, async nature of js, etc
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Q1. Behavioral round
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Round duration - 60 Minutes
Round difficulty - Medium

This was the DSA questions round. There were 2 questions. and both were basic questions.

Q1. 
Check If Linked List Is Palindrome
Given a singly linked list of integers, determine if the linked list is a palindrome.
Explanation:
A linked list is considered a palindrome if it reads the same forwar...read more
Ans. 
Check if a given singly linked list of integers is a palindrome or not.
• Create a function to reverse the linked list.

• Use two pointers to find the middle of the linked list.

• Compare the first half of the linked list with the reversed second half to determine if it's a palindrome.
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Q2. 
Segregate Odd-Even Problem Statement
In a wedding ceremony at NinjaLand, attendees are blindfolded. People from the bride’s side hold odd numbers, while people from the groom’s side hold even numbers. For...read more
Ans. 
Rearrange a linked list such that odd numbers appear before even numbers while preserving the order.
• Create two separate linked lists for odd and even numbers

• Traverse the original list and append nodes to respective odd/even lists

• Combine the odd and even lists while maintaining the order

• Return the rearranged linked list
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Round duration - 90 Minutes
Round difficulty - Easy

This was a subjective round where we have to code HTML, CSS, and JS. We were not allowed to use any external editor and their editor was just plain notepad so we couldn't even see the output but still, we completed it. Everyone at my college passed this round.

Round duration - 10080 Minutes
Round difficulty - Easy

Round duration - 120 Minutes
Round difficulty - Medium

In this round, the interviewer asked me to turn on screen mirroring. And then he gave me 1 more design which I needed to create in front of him in the next 2 hours. In the previous round, the focus was on HTML and CSS but in this round, the major focus was on JS. You are allowed to use google but not copy-paste the whole code.

Round duration - 90 Minutes
Round difficulty - Hard

This was an online interview with one of their employees. My interview was taken by their front-end lead. She was very helpful during the interview. You are allowed to search for documentation.

Round duration - 90 Minutes
Round difficulty - Easy

This was also a front-end interview round. The interviewer was again very helpful and I was allowed to google.

They have their own platform

Take home assignment

Q1. Live coding round of CRUD based small app.
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Q1. More on HTML, CSS, JS
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Q1. Promises, async/await, settimeout etc.
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I was asked 60 question with various snppits or problems to be solved within a time frame of 1 hour

3 dsa 2 medium 1 hard

To create a project in which i was asked to simply create a exact same page as given in design