CARS24 Senior Software Developer Interview Questions and Answers

Seat reservation system
bit manipulation
binary tree related

Q1. Bfs / dfs traversal 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.

Q1. The question was about Nodejs
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Q2. The question was to build a linked list in Nodejs
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Q1. The first question was related to DSA
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Q2. The question was related to SQL
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Basic coding only not to worry much

Q1. Tell me about ur self
Ans. 
I am a passionate software developer with experience in Java, Python, and web development.
• Experienced in Java, Python, and web development technologies

• Strong problem-solving skills

• Excellent team player with good communication skills
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Q2. What is ur projects
Ans. 
I have worked on various projects including a web-based inventory management system and a mobile app for tracking fitness goals.
• Developed a web-based inventory management system using React and Node.js

• Created a mobile app for tracking fitness goals using Flutter

• Implemented RESTful APIs for communication between frontend and backend systems
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Q1. Template and Reactive Forms in Angular
Ans. 
Template and Reactive Forms in Angular are two ways to handle forms in Angular applications.
• Template Forms are based on the traditional HTML forms and are easy to use for simple forms.

• Reactive Forms are more flexible and powerful, allowing for complex form validation and dynamic form controls.

• Template Forms use two-way data binding, while Reactive Forms use a more reactive approach with observables.

• Reactive Forms are r...read more
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