NJ India Invest Java Developer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Medium

The round consisted of 3 coding Questions and 20 Technical MCQs.

Q1. 
Connect Ropes Problem Statement
Given a number of ropes denoted as 'N' and an array containing the lengths of these ropes, your task is to connect the ropes into one single rope. The cost to connect two r...read more
Ans. 
The task is to find the minimum cost required to connect all the ropes by summing their lengths.
• Iterate through the ropes and connect the two shortest ropes at each step to minimize cost

• Use a priority queue to efficiently find the shortest ropes

• Keep track of the total cost as you connect the ropes

• Example: For input [4, 3, 2, 6], connect 2 and 3 (cost 5), then connect 4 and 5 (cost 9), then connect 9 and 6 (cost 15) for
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Q2. 
Idempotent Matrix Verification
Determine if a given N * N matrix is an idempotent matrix. A matrix is considered idempotent if it satisfies the following condition:
M * M = M
Input:
The first line cont...read more
Ans. 
Check if a given matrix is idempotent by verifying if M * M = M.
• Iterate through the matrix and multiply it with itself to check if it equals the original matrix.

• If the condition M * M = M is satisfied, then the matrix is idempotent.

• If the condition is not satisfied, then the matrix is not idempotent.
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Q3. 
Sum of LCM Problem Statement
Given an integer 'N', calculate and print the sum of the least common multiples (LCM) for each integer from 1 to N with N.
The sum is represented as:
LCM(1, N) + LCM(2, N) + ....read more
Ans. 
Calculate and print the sum of least common multiples (LCM) for each integer from 1 to N with N.
• Iterate from 1 to N and calculate LCM of each number with N

• Add all the calculated LCM values to get the final sum

• Return the sum for each test case
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Round duration - 120 minutes
Round difficulty - Medium

This round is a Long Coding Round. Every Candidate was assigned with a mentor who guides them, We were given a real-life scenario for which we have to construct a database with required tables. We should draw an ER Diagram to demonstrate the Database. After the Database Completion, We have to Start Coding the Application. The Design(like Placing the button or background colour) is not given much importance. They mainly test the practical knowledge of candidates in OOPS and expertise in a C, C++, Java, Android or any other language were OOPS Concepts can be applied.

Round duration - 180 Minutes
Round difficulty - Medium

This Round is a technical Interview. I was asked Questions to test my Technical Knowledge.

Q1. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an array of 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of 0s, 1s, and 2s while iterating through the array.

• Swap elements based on the values encountered to sort the array in-place.

• Time complexity of the algorithm should be O(N) where N is the size of the array.
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Round duration - 20 Minutes
Round difficulty - Easy