Blackrock Interview Questions, Process, and Tips for Freshers

Round duration - 100 Minutes
Round difficulty - Hard

There were 2 interviewers. It started with an introduction from me and one of the interviewers directly started with a DSA questions. Two problems were asked and I had to code them on a compiler of my choice by sharing my screen. Level of DSA question was medium but I was severely grilled on oops. I had to create different abstract classes, interface and explain entire oops with examples.

This was followed by a set of core JAVA questions :

Difference between == and .equals() ?
Mention some methods of the object class?
Difference between TreeSet and SortedSet?
How is a String saved in JAVA?
difference between string pool and heap memory?

Q1. 
Shortest Distance in a Binary Search Tree
Your task is to determine the shortest distance between two nodes with given keys in a Binary Search Tree (BST).
It is assured that both keys exist within the BS...read more
Ans. 
Find the shortest distance between two nodes in a Binary Search Tree.
• Traverse the BST to find the paths from the root to both nodes.

• Compare the paths to find the common ancestor node.

• Calculate the distance by adding the lengths of the paths from the common ancestor to both nodes.

• Return the shortest distance as the result.
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Q2. 
Greatest Common Divisor Problem Statement
You are tasked with finding the greatest common divisor (GCD) of two given numbers 'X' and 'Y'. The GCD is defined as the largest integer that divides both of the...read more
Ans. 
Find the greatest common divisor (GCD) of two given numbers 'X' and 'Y'.
• Iterate from 1 to the minimum of X and Y, check if both X and Y are divisible by the current number, update GCD if true

• Use Euclidean algorithm to find GCD: GCD(X, Y) = GCD(Y, X % Y)

• If one of the numbers is 0, the other number is the GCD

• Handle edge cases like when one of the numbers is 0 or negative
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Q3. 
Bridge in Graph Problem Statement
Given an undirected graph with V vertices and E edges, your task is to find all the bridges in this graph. A bridge is an edge that, when removed, increases the number of...read more
Ans. 
Find all the bridges in an undirected graph.
• Use Tarjan's algorithm to find bridges in the graph.

• A bridge is an edge whose removal increases the number of connected components.

• Check for bridges by removing each edge and running a DFS to see if the graph is still connected.
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Q1. Projects and basic of sql/python, Financial Knowledge
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Q1. Moreover on activities done in college, how would you solve a arguement between 2 colleagues
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Add the char of a float value till the sum is less than 9. eg. 107.6 = 1+7+0+6 = 14 = 1+4 = 5

Quiz- you have 3 bottles 5 ltr, 3 ltr and 2ltr. Extract 4 ltr of water from this.

Round duration - 87 minutes
Round difficulty - Medium

Timing : It was conducted in evening at 3 PM
The pacreception environment was very user friendly .
The platform was audio and video proctored.

Q1. 
Binary to Decimal Conversion
Convert a given binary number, represented as a string 'S' of size 'N', into its decimal equivalent integer and output it.
Input:
The first line contains an integer 'T', den...read more
Ans. 
Convert a binary string to its decimal equivalent integer.
• Iterate through the binary string from right to left, multiplying each digit by 2 raised to the power of its position.

• Add the results of the multiplication to get the decimal equivalent.

• Ensure the binary string consists only of '0' and '1' characters.

• Handle multiple test cases by repeating the conversion process for each case.
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Round duration - 80 minutes
Round difficulty - Medium

So This was a very interactive round . There were two interviewers , one male and one female . The male interviewer was quite experienced where as female interviewer was relatively new . The Interview started by a small introduction followed by some OOPS related questions where I was tested on how i perceive the concept of OOPS in real life . Then this conversation was followed by some core concepts of JAVA like abstract classes and interfaces . Then I was asked about my projects that i mentioned in my resume , then after some healthy discussion on those projects , the interviewer started to question about DBMS , I was asked some basic queries followed by some advanced queries and then followed by a discussion on SQL vs NoSQL . Then Interviewers asked me about my tech stack and the source of my technical knowledge. Then at last I was asked that why Blackrock and this concluded my Interview.

Q1. 
Ninja And The Triangle Problem Statement
Ninja is provided with 'N' stars and the task is to construct a triangle such that the 'i'th level of the triangle uses 'i' number of stars. The goal is to make th...read more
Ans. 
Given 'N' stars, construct a triangle with maximum height using 'i' stars in 'i'th level.
• Calculate the maximum height of the triangle using the formula: height = floor((-1 + sqrt(1 + 8 * N)) / 2)

• Iterate through each test case and calculate the maximum height for each 'N'.

• Output the maximum height for each test case.
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