CRED Mechanical Engineer Interview Questions and Answers

DS, Algo, DP, Greedy, Stack, Heap

Q1. System Design a DropBox
Ans. 
Design a scalable cloud storage system similar to DropBox.
• Use distributed file system for storing files across multiple servers.

• Implement data deduplication to save storage space.

• Use client-side encryption for security.

• Implement file synchronization across devices.

• Utilize load balancing to distribute user requests.

• Implement version control for files.

• Use metadata for efficient file organization.
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Q2. Design a Linked List
Ans. 
A linked list is a linear data structure where each element is a separate object with a reference to the next element.
• Start with a Node class that has data and a reference to the next node

• Create a LinkedList class that manages the nodes and provides methods like insert, delete, and search

• Example: Node class - data, next; LinkedList class - head, insert(data), delete(data), search(data)
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Q1. About yourself. Projects worked upon
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Q2. Why want to join Ocrolus?
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OnlineCoding Test for 60 mins

Q1. 2 DSA question for 1 hour
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Q1. Technical Question around CS concepts
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Test was based on arrays and some dsa concepts.

Q1. Does Java support pass by reference?
Ans. 
Yes
• Java uses pass by value for all variables, including object references.

• When an object reference is passed as an argument, a copy of the reference is passed, not the actual object.

• Modifying the reference inside the method will not affect the original reference outside the method.

• However, modifications to the object's state inside the method will be visible outside the method.
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Q2. Explain Singleton Pattern
Ans. 
Singleton pattern restricts the instantiation of a class to a single object.
• Singleton pattern ensures that only one instance of a class exists throughout the application.

• It provides a global point of access to the instance.

• Commonly used in scenarios where a single instance needs to coordinate actions across the system.

• Example: Database connection manager, logger, configuration manager.
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Q1. Internal Implementation of HashMap
Ans. 
HashMap is implemented using an array of linked lists to handle collisions.
• HashMap stores key-value pairs in an array of linked lists

• Hash function is used to determine the index of the array where the key-value pair will be stored

• Collision handling is done by chaining, where multiple key-value pairs with the same hash value are stored in the same linked list

• HashMap allows null keys and values

• HashMap is not synchronized...read more
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Round duration - 90 minutes
Round difficulty - Medium

Timing was 9 PM. Platform was not good. Platform was very lagging so overall it was bad experience.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where the array has less than 3 elements separately.

• Use a set to store distinct elements for efficient processing.
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Q2. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The task is to find the longest palindromic substring within STR. If there are several palindromic substring...read more
Ans. 
Find the longest palindromic substring in a given string.
• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found so far

• Return the longest palindromic substring
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Q3. 
Ninja and Geometry Problem Statement
In this problem, Ninja is provided with two lines on a 2D plane. The first line 'AB' is determined by two points A and B. The second line 'PQ' is determined by two poi...read more
Ans. 
Calculate the intersection point of two lines on a 2D plane with precision up to six decimal places.
• Implement a function to calculate the intersection point of two lines on a 2D plane

• Handle precision up to six decimal places in the output

• Return -1.000000 -1.000000 if the lines do not intersect

• Ensure the lines 'AB' and 'PQ' are distinct
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Round duration - 90 minutes
Round difficulty - Medium

Timing was 9 PM. Platform was not good. Platform was very lagging so overall it was bad experience.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where there are less than 3 elements in the array.

• Consider edge cases like negative integers and duplicates.
Answered by AI
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Q2. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The goal is to identify the longest palindromic substring within this string. In cases where multiple palind...read more
Ans. 
Identify the longest palindromic substring in a given string.
• Iterate through each character in the string and expand around it to find palindromes

• Keep track of the longest palindrome found so far

• Return the longest palindromic substring with the smallest start index
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Q3. 
Ninja and Geometry Problem Statement
In this problem, Ninja is provided with two lines on a 2D plane. The first line 'AB' is determined by two points A and B. The second line 'PQ' is determined by two poi...read more
Ans. 
Calculate the intersection point of two lines on a 2D plane with precision up to six decimal places.
• Implement a function to calculate the intersection point of two lines on a 2D plane

• Handle precision up to six decimal places in the output

• Return -1.000000 -1.000000 if the lines do not intersect

• Ensure the lines 'AB' and 'PQ' are distinct
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Round duration - 90 minutes
Round difficulty - Hard

Timing was 9 PM. Platform was not good. Platform was very lagging so overall it was bad experience.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where the array has less than 3 elements separately.

• Consider using a set to ensure distinct elements in the array.
Answered by AI
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Q2. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The goal is to identify the longest palindromic substring within this string. In cases where multiple palind...read more
Ans. 
Identify the longest palindromic substring in a given string.
• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found

• Return the longest palindromic substring with the smallest start index
Answered by AI
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Q3. 
Ninja and Geometry Problem Statement
In this problem, Ninja is provided with two lines on a 2D plane. The first line 'AB' is determined by two points A and B. The second line 'PQ' is determined by two poi...read more
Ans. 
Calculate the intersection point of two lines on a 2D plane with precision up to six decimal places.
• Use the formula for finding the intersection point of two lines in 2D space.

• Handle precision issues that may arise due to floating-point arithmetic.

• Return -1.000000 -1.000000 if the lines do not intersect.

• Ensure the lines 'AB' and 'PQ' are distinct.
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Round duration - 50 mins
Round difficulty - Medium

First round was coding round, where i was asked 2 DS algo questions, 1 was easy and other was of medium difficulty

Q1. 
Shortest Path in a Binary Matrix Problem Statement
Given a binary matrix of size N * M where each element is either 0 or 1, find the shortest path from a source cell to a destination cell, consisting only...read more
Ans. 
Find the shortest path in a binary matrix from a source cell to a destination cell consisting only of 1s.
• Use Breadth First Search (BFS) algorithm to find the shortest path.

• Keep track of visited cells to avoid revisiting them.

• Update the path length as you traverse through the matrix.

• Return -1 if no valid path exists.
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Round duration - 50 mins
Round difficulty - Easy

I was asked to design url shortner

Q1. Can you explain how you would design a URL shortener?
Ans. 
Design a URL shortener system
• Generate a unique short code for each URL

• Store the mapping of short code to original URL in a database

• Redirect users from short URL to original URL when accessed

• Consider implementing features like custom short codes, expiration dates, and analytics

• Ensure scalability and performance by using distributed systems and caching
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Round duration - 50 mins
Round difficulty - Medium

This was hiring manager round

Q1. Can you discuss a coding problem you encountered, your past projects, and any behavioral questions related to your experiences?
Ans. 
Discussed coding problem, past projects, and behavioral questions in SDE - 1 interview.
• Coding problem: Discussed how I optimized a sorting algorithm in a previous project.

• Past projects: Talked about a web application I developed using React and Node.js.

• Behavioral questions: Shared how I handled a conflict within a team during a project.

• Example: Explained how I implemented a feature in a mobile app that improved user en
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