Blackrock Senior Java Developer Interview Questions and Answers

Tell me about a time where you resolve a conflict

Reverse a string, identify anagram

70 minutes test, and 4 questions

Q1. Behavioural Queston
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DSA medium level questions were asked.

Q1. Design MakeMyTrip kind of application.
Ans. 
MakeMyTrip is a travel booking application that allows users to book flights, hotels, and holiday packages.
• Include features like flight/hotel search, booking, payment gateway integration, and user profiles.

• Implement filters for search results, reviews/ratings for hotels, and notifications for booking updates.

• Integrate maps for location tracking, weather forecasts, and customer support chatbot.

• Offer discounts, loyalty p...read more
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Q2. Oops based questions.
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Round duration - 60 minutes
Round difficulty - Easy

This was the qualification round which comprised of several MCQs and 3 coding questions.
It was held on Hackerearth from 3:00 PM to 4:00 PM.
Use of any other IDE was prohibited.

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 to identify the bug.

• Make necessary corrections based on the iden...read more
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Q2. 
Print Nodes at Distance K from a Given Node
Given an arbitrary binary tree, a node of the tree, and an integer 'K', find all nodes that are at a distance K from the specified node, and return a list of th...read more
Ans. 
Given a binary tree, a target node, and an integer K, find all nodes at distance K from the target node.
• Traverse the binary tree to find the target node.

• Use BFS to traverse the tree from the target node to nodes at distance K.

• Keep track of the distance while traversing the tree.

• Return the values of nodes at distance K in any order.
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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 the 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 - Easy

Consisted of 3 DSA questions and MCQ on python proficiency

Q1. 
Palindromic Substrings Problem Statement
Given a string S, your task is to return all distinct palindromic substrings of the given string in alphabetical order.
Explanation:
A string is considered a pal...read more
Ans. 
Return all distinct palindromic substrings of a given string in alphabetical order.
• Iterate through all possible substrings of the given string.

• Check if each substring is a palindrome by comparing it with its reverse.

• Store all palindromic substrings in a set to ensure uniqueness.

• Return the sorted list of palindromic substrings.
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Round duration - 60 minutes
Round difficulty - Medium

It was a pure DSA round and interviewer was very helpful with providing significant hints to solve the given problems

Q1. 
Island Perimeter Calculation Problem
Given a binary grid representation of a map of an island, calculate the perimeter of the island. The grid uses '0' for water and '1' for land.
The grid has only one i...read more
Ans. 
Calculate the perimeter of an island represented by a binary grid.
• Iterate through the grid and count the perimeter based on land cells and their adjacent cells.

• Each land cell contributes 4 units to the perimeter, subtract 2 units for each adjacent land cell.

• Handle edge cases where land cells are at the boundaries of the grid.

• Return the total perimeter for each test case.
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Round duration - 60 minutes
Round difficulty - Hard

DSA+OS

Q1. 
Clearing the Forest Problem Statement
Ninja lives in a city called Byteland where a festive event is being organized. To make space for this event, Ninja is tasked with clearing a nearby forest. The fores...read more
Ans. 
Calculate the minimum number of steps Ninja needs to cut down all trees in a forest grid.
• Iterate through the grid to find the shortest path to cut down all trees in order.

• Use a priority queue to keep track of the shortest trees to cut next.

• If it's impossible to cut all trees, return -1.

• Consider all four cardinal directions for movement in the grid.
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It was angular and java

Q1. A question about dbms etc
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Q1. 1st round was virtual round basic queation of core java , design pattern, threading object creation singleton design pattern deep ,threading class level objevt level,collection differances java 8 stream...read more
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Q2. Singleton design implementation and deep dive into it
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Q3. Immutable implementation ,design classes interfaces with certain scenario
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Q1. Need to visit Nomura office
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Q2. Data structure questions arraylist linked list stack queue imple
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Q3. BFS related question
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Q4. Data structure related questions
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