NJ Technologies Java Full Stack Developer Interview Questions and Answers

Code was of leetcode medium level.

Q1. Easy level DS code
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Q2. Question related to database
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Q1. Questions related to SQL
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Q2. Inner join of three tables
Ans. 
Inner join of three tables in SQL
• Use the JOIN keyword to combine three tables based on a common column

• Specify the columns to select from each table

• Use the ON keyword to specify the join condition
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Q3. What is cross join
Ans. 
Cross join is a type of join operation in SQL that returns the Cartesian product of two tables.
• Cross join does not require any matching condition between the tables.

• It combines each row from the first table with every row from the second table.

• Cross join can result in a large number of rows if the tables are big.

• Example: SELECT * FROM table1 CROSS JOIN table2;
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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. Oops? .net core features
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Aptitude questions with 2-3 coding questions

Q1. Input-wwwrrrrttttuu Output - w3r4t4u2
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Q2. Interpreter vs compiler
Ans. 
Interpreter executes code line by line, compiler translates code into machine code before execution.
• Interpreter translates code into machine code line by line during runtime

• Compiler translates code into machine code before execution

• Interpreted languages include Python, JavaScript

• Compiled languages include C, C++
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Round duration - 120 minutes
Round difficulty - Hard

This round was very difficult. I never do these much difficulty level of coding questions. But i give my best, and just do every questions by using step by step process.

Q1. 
Hourglass Pattern Problem Statement
Given an integer 'N', print an hourglass pattern based on the value of 'N'.
Input:
The first and only line of input contains an integer, denoting the value of N.
Out...read more
Ans. 
Print an hourglass pattern based on the given integer 'N'.
• Read the integer 'N' as input

• Print the top half of the hourglass pattern with decreasing numbers

• Print the bottom half of the hourglass pattern with increasing numbers

• Handle the constraints for 'N' values between 1 and 50
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Q2. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal in a disconnected graph starting from vertex 0.
• Use BFS algorithm to traverse the graph starting from vertex 0.

• Explore neighbor nodes first before moving to the next level neighbors.

• Consider bidirectional edges in an undirected graph.

• Output the BFS traversal sequence for each test case in a separate line.

• Ensure the BFS path starts from vertex 0 and print connected nodes in numerical sort order.
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Q3. 
Sort a Stack Problem Statement
You are given a stack. Your task is to sort the elements within the stack in ascending order using only push and pop operations. You are allowed to use one additional stack ...read more
Ans. 
Sort a given stack in ascending order using only push and pop operations with the help of an additional stack.
• Use one additional stack to assist in sorting the elements.

• Pop elements from the input stack and push them onto the auxiliary stack in sorted order.

• Keep track of the current minimum element to maintain ascending order.

• Pop elements from the auxiliary stack back to the input stack to get the sorted order.
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Round duration - 90 minutes
Round difficulty - Easy

This round is also coding round in this round we have a small video call interaction too, in which hr ask few questions to only those whose coding question is correct.

Q1. 
Next Smaller Palindrome Problem Statement
You are given a palindrome number represented as a string S. Your task is to find the largest palindrome number that is strictly less than S.
Example:
Input:
T...read more
Ans. 
Find the largest palindrome number strictly less than a given palindrome number.
• Iterate from the middle towards the start of the number and decrement the digits to create the largest palindrome less than the given number.

• Handle cases where the number is all '9's by changing the middle digit to '9' and decrementing the rest of the digits.

• If the number has an odd length, simply mirror the first half to create the largest
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Q2. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. 
Find minimum time to rot all fresh oranges adjacent to rotten oranges in a grid.
• Use Breadth First Search (BFS) to simulate the rotting process.

• Track the time taken to rot all fresh oranges.

• Return -1 if all fresh oranges cannot be rotten.

• Handle edge cases like empty grid or no fresh oranges.
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Coding was hard conducted on the platform called interview.io

Consits of 2 q 1 is Dp, and the other is Graph

Bit harder compared to other companies

Reasoning like questions