Blackrock interview experience Real time questions & tips from candidates to crack your interview

SDE - 1

Blackrock
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3 rounds | 4 Coding problems

Interview preparation journey

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Preparation
Duration: 5 months
Topics: DSA and Other core subjects like OOPS, Operating systems, Computer Networking and DBMS
Tip
Tip

Tip 1 : Do a minimum of 3 problems everyday. Discipline is important.
Tip 2 : Give mock interviews while explaining your approach.
Tip 3 : Understand and learn different approaches to a problem and dissect them.

Application process
Where: Campus
Eligibility: above 7 CGPA, no backlogs
Resume Tip
Resume tip

Tip 1 : Prepare on everything that you have put on your resume.
Tip 2 : Make a one-pager resume. This shows that you can be concise and brief in your demonstration.

Interview rounds

01
Round
Medium
Online Coding Interview
Duration90 minutes
Interview date20 Aug 2021
Coding problem1

This round involved majorly on MCQ questions ranging from all topics that are taught in Computer Science. MCQ involved short coding, time and space complexities, corrections and other DSA topics.

1. Operating System Question

round robin mcq

Problem approach

Tip 1 : understand the problem
Tip 2 : calculate thoroughly and check before answering

02
Round
Hard
Video Call
Duration60 Minutes
Interview date23 May 2022
Coding problem2

The round was a video call on webex. The interview greeted and asked me to introduce myself. After that we jumped straight into coding.

1. Shortest Path in a Binary Matrix

Moderate
37m average time
65% success
0/80
Asked in companies
SamsungOracleAmazon

You have been given a binary matrix of size 'N' * 'M' where each element is either 0 or 1. You are also given a source and a destination cell, both of them lie within the matrix.

Your task is to find the length of the shortest path from the source cell to the destination cell only consisting of 1s. If there is no path from source to destination cell, return -1.

Note:
1. Coordinates of the cells are given in 0-based indexing.
2. You can move in 4 directions (Up, Down, Left, Right) from a cell.
3. The length of the path is the number of 1s lying in the path.
4. The source cell is always filled with 1.
For example -
1 0 1
1 1 1
1 1 1
For the given binary matrix and source cell(0,0) and destination cell(0,2). Few valid paths consisting of only 1s are

X 0 X     X 0 X 
X X X     X 1 X 
1 1 1     X X X 
The length of the shortest path is 5.
Problem approach

I had to mark the rocks and 1 and free paths as 0.
After that, it was a simple BFS algorithm application which would give the result.

Try solving now

2. Trapping Rain Water

Moderate
15m average time
80% success
0/80
Asked in companies
RazorpayMorgan StanleyUber

You have been given a long type array/list 'arr’ of size 'n’.


It represents an elevation map wherein 'arr[i]’ denotes the elevation of the 'ith' bar.



Note :
The width of each bar is the same and is equal to 1.
Example:
Input: ‘n’ = 6, ‘arr’ = [3, 0, 0, 2, 0, 4].

Output: 10

Explanation: Refer to the image for better comprehension:

Alt Text

Note :
You don't need to print anything. It has already been taken care of. Just implement the given function.
Problem approach

I created two array name ( maxleft, maxright ) which will store the maximum left and maximum right for each height. We will use these array to calculate the stored water in each height.

stored water = min(maxleft,maxright) - height. This is the formula to calculate the stored water.

Try solving now
03
Round
Easy
HR Round
Duration30 Minutes
Interview date24 May 2022
Coding problem1

The HR greeted herself and then proceeded asking me multiple behavioral questions and preferences.

1. Basic HR question

If there was a problem in my team, how would I solve it?

Problem approach

Tip 1 : Prepare for these questions well in advances
Tip 2 : Follow STAR model while answering
Tip 3 : Be very clear and crisp while answering them

Here's your problem of the day

Solving this problem will increase your chance to get selected in this company

Skill covered: Programming

What is recursion?

Choose another skill to practice
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