RenewBuy Software Developer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
0/1 Knapsack Problem Statement
A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of...read more
Ans. 
Yes, the 0/1 Knapsack problem can be solved using dynamic programming with a space complexity of not more than O(W).
• Use a 1D array to store the maximum value that can be stolen for each weight capacity from 0 to W.

• Iterate through each item and update the array based on whether including the item would increase the total value.

• The final value in the array at index W will be the maximum value that can be stolen.
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Q2. 
Find the Second Largest Element
Given an array or list of integers 'ARR', identify the second largest element in 'ARR'.
If a second largest element does not exist, return -1.
Example:
Input:
ARR = [2,...read more
Ans. 
Find the second largest element in an array of integers.
• Iterate through the array to find the largest and second largest elements.

• Handle cases where all elements are identical.

• Return -1 if a second largest element does not exist.
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Round duration - 60 Minutes
Round difficulty - Easy

System Design Round

Q1. Design a system for Twitter, discussing its architecture, key components, and scalability considerations.
Ans. 
Design a scalable system for Twitter with key components and architecture.
• Use microservices architecture for scalability and fault isolation.

• Key components include user service, tweet service, timeline service, and notification service.

• Use a distributed database like Cassandra for storing tweets and user data.

• Implement a message queue like Kafka for handling real-time updates and notifications.

• Use a caching layer like ...read more
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Round duration - 30 Minutes
Round difficulty - Easy

It is just a formality

Q1. Explain Deadlock?
Ans. 
Deadlock is a situation in computing where two or more processes cannot proceed because each is waiting for the other to release resources.
• Occurs in multi-threaded environments when processes hold resources and wait for others.

• Example: Process A holds Resource 1 and waits for Resource 2, while Process B holds Resource 2 and waits for Resource 1.

• Can lead to system inefficiency and unresponsiveness.

• Deadlock detection and...read more
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Q2. Explain Red Black Tree?
Ans. 
A Red-Black Tree is a balanced binary search tree with specific properties to ensure efficient operations.
• Each node is colored either red or black.

• The root node is always black.

• Red nodes cannot have red children (no two reds in a row).

• Every path from a node to its descendant leaves must have the same number of black nodes.

• This structure ensures O(log n) time complexity for insertion, deletion, and search operations.

• Exa...read more
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Q3. Find local minima in a 1-D array?
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Q4. Find local minima in 2-D array?
Ans. 
Local minima in a 2-D array are elements smaller than their neighbors. We can find them using various algorithms.
• A local minimum is defined as an element that is less than its adjacent elements.

• For example, in the array [[9, 8, 7], [6, 5, 4], [3, 2, 1]], the element 1 is a local minimum.

• To find local minima, iterate through each element and compare it with its neighbors (up, down, left, right).

• Consider edge cases where...read more
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Round duration - 60 minutes
Round difficulty - Easy

The round consisted of 2 coding Problems and it lasted for 60 minutes from 12:00 PM to 1:00 PM on Hackerearth.
Use of other IDEs was prohibited and video was on.

Q1. 
Implement indexOf Function
You are provided with two strings A and B. Your task is to find the index of the first occurrence of A within B. If A is not found in B, return -1.
Example:
Input:
A = "bc", ...read more
Ans. 
Implement a function to find the index of the first occurrence of one string within another string.
• Iterate through the second string and check if a substring of the same length as the first string matches the first string.

• Return the index of the first occurrence of the first string within the second string, or -1 if not found.

• Handle edge cases like empty strings or when the first string is longer than the second string...read more
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Q2. 
Problem: Search In Rotated Sorted Array
Given a sorted array that has been rotated clockwise by an unknown amount, you need to answer Q queries. Each query is represented by an integer Q[i], and you must ...read more
Ans. 
Search for integers in a rotated sorted array efficiently.
• Implement binary search to find the target integer in the rotated array.

• Handle the rotation by checking which side of the array is sorted before performing binary search.

• Return the index of the target integer if found, else return -1.

• Time complexity of O(logN) is required for each query.
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Round duration - 60 minutes
Round difficulty - Medium

The round was conducted on Google Meet with 2 interviewers . They were friendly and helpful.
The timing was 12:00 to 1:00 PM.
Our Video was on .

Q1. 
Distinct Subsequences Problem Statement
You are given a string 'S' of length 'N' which may include duplicate alphabets. Your goal is to calculate the number of distinct subsequences in the string.
Exampl...read more
Ans. 
Calculate the number of distinct subsequences in a string with possible duplicates.
• Use dynamic programming to keep track of the count of distinct subsequences for each character in the string.

• Consider the cases where the current character is included or excluded in the subsequence.

• Handle duplicates by considering the previous occurrence of the character.

• Return the count of distinct subsequences modulo 10^9 + 7.
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Round duration - 60 minutes
Round difficulty - Easy

This was a Behavioral Round. It lasted for 45-50 minutes. It consisted of a discussion on my projects. The interviewer was very impressed by the way I explained my projects. She even appreciated me for that. This was followed by normal HR questions .Timing of This round was 4:00 PM to 5:00 PM

Sorting of an array and aptitude

Q1. BFS graph traversal
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Q1. Binary tree question
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Round duration - 90 minutes
Round difficulty - Medium

The test was conducted in the evening from 5:00 pm to 6:30 pm. Because of the covid situation, all the students attempted the test from their homes. But it was a webcam-based test to avoid any kind of cheating.
There were 3 coding problems to be done in 90 minutes.
After resume based shortlisting, 70 candidates were selected to appear for the test out of which 30 were shortlisted for interviews.

Q1. 
Amazing Strings Problem Statement
Determine if the third string contains all the characters from both the first and second strings in any order. If so, return "YES"; otherwise, return "NO".
Input:
Line ...read more
Ans. 
Check if the third string contains all characters from the first and second strings in any order.
• Create a frequency map for characters in the first and second strings.

• Check if all characters in the third string are present in the frequency map.

• Ensure the count of characters in the third string matches the count in the frequency map.

• Return 'YES' if all conditions are met, otherwise return 'NO'.
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Q2. 
Shortest Path Visiting All Nodes
You are given a connected undirected unweighted graph comprising 'N' nodes and 'M' edges. In this graph, each pair of connected nodes is linked by exactly one undirected e...read more
Ans. 
Find the length of the shortest path visiting all nodes in a connected undirected unweighted graph.
• Use Breadth First Search (BFS) to find the shortest path that visits all nodes at least once.

• Maintain a bitmask to keep track of visited nodes and their states.

• Consider all possible permutations of nodes to find the shortest path length.
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Q3. 
Meeting Rooms Allocation Problem Statement
Stark Industry is planning to organize meetings for various departments in preparation for Stark Expo. Due to limited rooms in Stark Tower, the goal is to alloca...read more
Ans. 
Determine the minimum number of conference rooms required for scheduling meetings.
• Sort the meetings by start time.

• Iterate through the meetings and keep track of rooms needed based on overlapping times.

• Use a priority queue to efficiently allocate rooms.

• Example: For meetings (1pm-4pm), (3pm-5pm), (4pm-6pm), 2 rooms are required.

• Ensure linear time complexity by optimizing the room allocation process.
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Round duration - 50 minutes
Round difficulty - Medium

This round started at 9 am and went till 4 pm.
Out of 70 students that appeared in online coding test, 30 were shortlisted for the first round (this round) of interviews.
In this round, everyone was asked one moderate level coding question. The interviewer provided the link to an IDE, where I wrote my code.
The interview started with the introduction being followed by 1 coding problem. In the end, the interviewer asked me if I wanted to ask any questions. To which I asked him my feedback so that I can improve my wear areas.
Of the 30 candidates, 17 were selected for the final interview round.

Q1. 
Print All Subsets Challenge
Given an array arr containing 'N' distinct integers, your task is to generate all possible non-empty subsets of this array.
Note: While the elements within each subset should ...read more
Ans. 
Generate all possible non-empty subsets of an array of distinct integers.
• Use recursion to generate all subsets by including or excluding each element in the array.

• Maintain a current subset and add it to the result when reaching the end of the array.

• Ensure elements within each subset are in increasing order.

• Handle the input and output format as specified in the question.
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Round duration - 50 minutes
Round difficulty - Easy

This was a technical + HR round. Started in the evening at 4:30 pm, this round went till 9:30 pm.
17 students were shortlisted for this final round of interview.
This interview was also virtual and involved both technical and HR-related questions. The interview started with an introduction and then questions based on my resume were asked.
Out of 17 candidates, 8 candidates got a full-time offer from Urban Company.

Q1. 
Find Row With Maximum 1's in a Sorted 2D Matrix
You are provided with a 2D matrix containing only the integers 0 or 1. The matrix has dimensions N x M, and each row is sorted in non-decreasing order. Your...read more
Ans. 
Find the row with the maximum number of 1's in a sorted 2D matrix.
• Iterate through each row of the matrix and count the number of 1's in each row.

• Keep track of the row index with the maximum number of 1's seen so far.

• Return the index of the row with the maximum number of 1's.

• If multiple rows have the same number of 1's, return the row with the smallest index.
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Round duration - 75 minutes
Round difficulty - Medium

The test had 3 questions which had to solved in 75 minutes.The test was of medium difficulty.

Q1. 
Meeting Rooms Allocation Problem Statement
Stark Industry is planning to organize meetings for various departments in preparation for Stark Expo. Due to limited rooms in Stark Tower, the goal is to alloca...read more
Ans. 
Determine the minimum number of conference rooms needed to schedule meetings without overlap.
• Sort the meetings by start time.

• Iterate through the meetings and keep track of the rooms in use.

• If a meeting starts after another ends, it can reuse the same room.

• If a meeting starts before another ends, a new room is needed.

• Return the maximum number of rooms in use at any point.
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Q2. 
Maximize XOR Value
You are provided with an integer X and are tasked with identifying an integer Y such that the bitwise XOR operation between X and Y yields the maximum possible value. The condition is t...read more
Ans. 
Find an integer Y such that XOR operation with X yields maximum value within given constraints.
• Iterate from the most significant bit to find the highest bit that can be toggled to maximize XOR value.

• To maximize XOR value, toggle the highest bit of X to 0 and all lower bits to 1.

• Ensure the final Y does not exceed (2^61) - 1.

• Example: For X = 3, the highest bit to toggle is at position 61, so Y = 2305843009213693950.

• Examp...read more
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Q3. 
Minimize Maximum Difference Between Adjacent Elements
You are provided with a non-decreasing array and an integer K. Your task is to remove exactly K elements from this array so that the maximum differenc...read more
Ans. 
Remove K elements from a non-decreasing array to minimize the maximum difference between adjacent elements.
• Sort the array in non-decreasing order.

• Iterate through the array and calculate the difference between adjacent elements.

• Remove elements to minimize the maximum difference.

• Return the minimized maximum difference.
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Round duration - 60 minutes
Round difficulty - Easy

The interview was taken by SDE2 and she was very friendly. All the questions asked were related to DS and algo. The first 10 minutes were used for introductions and the last 5 minutes were reserved for any questions that I have. Always try to ask meaningful questions at the end of the interview.

Q1. 
Frequency in a Sorted Array Problem Statement
Given a sorted array ARR and a number X, your task is to determine the count of occurrences of X within ARR.
Note:
• If X is not found in the array, return...read more
Ans. 
Count occurrences of a number in a sorted array efficiently.
• Use binary search to find the first and last occurrence of the target number in the array.

• Calculate the count of occurrences by subtracting the indices of the last and first occurrences.

• Handle cases where the target number is not found in the array.

• Time complexity: O(log(N)), Space complexity: O(1).
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Q2. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. 
Find the minimum time required to rot all fresh oranges in a grid.
• Use Breadth First Search (BFS) to simulate the rotting process

• Track the time taken to rot all oranges and return -1 if any fresh oranges remain

• Handle edge cases such as no fresh oranges or all oranges already rotten

• Consider using a queue to efficiently process neighboring oranges
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Q3. 
Clone Linked List with Random Pointer Problem Statement
Given a linked list where each node has two pointers: one pointing to the next node and another which can point randomly to any node in the list or ...read more
Ans. 
Yes, the cloning of a linked list with random pointer can be accomplished without utilizing extra space.
• Use a hashmap to store the mapping between original nodes and cloned nodes.

• Iterate through the original linked list to create the cloned linked list by mapping the random pointers using the hashmap.

• Time complexity of this approach is O(N) where N is the number of nodes in the linked list.
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Round duration - 60 minutes
Round difficulty - Medium

The focus of this round was mainly on my projects and internships. It was taken by a Senior SDE and it more of a technical interaction. I was asked in-depth about my projects and most of the questions asked around OS/DBMS were based on my projects.
The interviewer wanted to judge whether I have core knowledge about subjects like OS and DBMS and also about the projects that I had done.

Round duration - 60 minutes
Round difficulty - Easy

It was the culture fit round taken by the Director of Engineering.