Blackrock Applications Engineer Interview Questions and Answers

Q1. Basic questions related to resume
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Q2. Technical questions related to language you known
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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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Q1. About projects in resume
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Q2. Resume related questions
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Q1. Tell me about Trade life cycle?
Ans. 
Trade life cycle refers to the stages involved in a trade from initiation to settlement.
• Initiation: Trade is proposed and agreed upon by parties involved.

• Execution: Trade is carried out as per agreed terms.

• Confirmation: Parties confirm details of the trade.

• Clearing: Trade details are matched and processed.

• Settlement: Actual exchange of funds and securities takes place.

• Post-trade processing: Reconciliation and reporting
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Q2. Tell me about Financial products?
Ans. 
Financial products are instruments that help individuals and organizations manage their financial resources and achieve specific financial goals.
• Financial products can include savings accounts, certificates of deposit, stocks, bonds, mutual funds, and insurance policies.

• They are designed to provide a range of benefits such as capital appreciation, income generation, risk management, and wealth preservation.

• Investors ca...read more
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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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Round duration - 70 Minutes
Round difficulty - Hard

The test link was active for a week, and you can give anytime you like. The IDE was very good and self explanatory. There were 2 coding questions and 15 aptitude questions.

Q1. 
Unweighted Graph Shortest Path Problem
You are tasked with finding the shortest path between two houses in the city of Ninjaland, represented as an unweighted graph. The city has N houses numbered from 1 ...read more
Ans. 
Find the shortest path between two houses in a city represented as an unweighted graph.
• Use breadth-first search (BFS) algorithm to find the shortest path in an unweighted graph.

• Start BFS from the source house and keep track of the path taken to reach each house.

• Once the destination house is reached, backtrack from destination to source to find the shortest path.

• Consider using a queue data structure to implement BFS eff...read more
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Q2. 
Check If Two Nodes Are Cousins
You are given an arbitrary binary tree consisting of N nodes, where each node is associated with a certain value, and two node values, a and b. Your task is to determine if ...read more
Ans. 
Check if two nodes in a binary tree are cousins by comparing their levels and parents.
• Traverse the tree to find the levels and parents of the given nodes.

• Compare the levels and parents of the two nodes to determine if they are cousins.

• If the levels are the same and the parents are different, the nodes are cousins.
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Round duration - 60 Minutes
Round difficulty - Medium

It contained two programming questions.

Q1. 
Counting Nodes in a Complete Binary Tree - Problem Statement
Given the root of a complete binary tree, calculate the total number of nodes in this tree.
A complete binary tree is defined as a binary tree...read more
Ans. 
Count the total number of nodes in a complete binary tree given its root.
• Traverse the tree in level order and count the nodes

• Use a queue to keep track of nodes at each level

• Check for null nodes represented by -1 in the input

• The total number of nodes in the example tree is 7
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Q2. 
Rearrange Array Numbers for Largest Possible Number
Given an array ARR consisting of non-negative integers, rearrange the numbers to form the largest possible numerical value. You are not permitted to alt...read more
Ans. 
Rearrange array numbers to form the largest possible numerical value by combining digits of each number in the array.
• Convert integers in the array to strings for easier manipulation.

• Sort the array of strings in non-increasing order based on custom comparison function.

• Join the sorted strings to form the largest possible number.
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Round duration - 60 Minutes
Round difficulty - Medium

This was more of a interaction round with some technical skills.

Q1. Can you explain the ACID properties and the rollback mechanism in DBMS?
Ans. 
ACID properties ensure database transactions are processed reliably. Rollback mechanism undoes changes if transaction fails.
• ACID properties: Atomicity, Consistency, Isolation, Durability

• Atomicity ensures all operations in a transaction are completed successfully or none at all

• Consistency ensures database remains in a valid state before and after transaction

• Isolation ensures transactions are independent and do not inter...read more
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Round duration - 45 Minutes
Round difficulty - Easy

The interviewer was friendly. Explained the question well. Allowed to use any preferred platform to write code.

Q1. 
Best Time to Buy and Sell Stock Problem Statement
Given an array prices representing the prices of a stock where each element indicates the price at a given minute, determine the maximum profit you can ac...read more
Ans. 
Find the maximum profit by buying and selling a stock once based on given prices.
• Iterate through the prices array and keep track of the minimum price seen so far and the maximum profit achievable.

• Calculate the profit by subtracting the current price from the minimum price and update the maximum profit if needed.

• Return the maximum profit, ensuring it is not negative.

• Example: prices = [2, 100, 150, 120], Buy at 2, sell a
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Dance Team Pairing Challenge
Imagine you are helping Ninja, a dance coach, who needs to form dance pairs from the available boys and girls in a studio. Given the number of boys N, the number of girls M, a...read more
Ans. 
The challenge involves forming dance pairs from available boys and girls based on potential pairings to maximize the number of pairs.
• Parse the input to get the number of test cases, boys, girls, and potential pairings.

• Iterate through the potential pairings and form pairs based on the given indexes.

• Output '1' if a set of maximum possible pairs is returned, else output '0'.

• There can be multiple valid configurations of pa...read more
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Q2. What is the difference between multiprocessing and multithreading?
Ans. 
Multiprocessing involves multiple processes running concurrently, while multithreading involves multiple threads within a single process.
• Multiprocessing utilizes multiple processes to execute tasks simultaneously.

• Multithreading involves multiple threads within a single process sharing the same memory space.

• Multiprocessing is typically used for CPU-bound tasks, while multithreading is more suitable for I/O-bound tasks.

• E...read more
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Round duration - 60 Minutes
Round difficulty - Hard

Q1. Can you describe the classes and functions involved in the design of a system like Splitwise?
Ans. 
Splitwise is a system for managing shared expenses among groups of people.
• Classes: User, Expense, Group

• Functions: addExpense(), settleUp(), calculateBalance()
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Round duration - 60 Minutes
Round difficulty - Hard