DigitalOcean Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

This was a 60 minute technical round involving questions based on data structures, OOPS concepts, DBMS and projects that I had mentioned in my resume.

Q1. 
Nth Fibonacci Number Problem Statement
Calculate the Nth term in the Fibonacci sequence, where the sequence is defined as follows: F(n) = F(n-1) + F(n-2), with initial conditions F(1) = F(2) = 1.
Input:
...read more
Ans. 
Calculate the Nth Fibonacci number efficiently using recursion or dynamic programming.
• Implement a recursive function to calculate the Nth Fibonacci number.

• Use memoization to store previously calculated Fibonacci numbers for efficiency.

• Consider using dynamic programming to optimize the solution.

• Handle edge cases such as N = 1 or N = 2 separately.

• Ensure the solution works efficiently for large values of N (up to 10000).
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Q2. Can you provide a program demonstrating operator overloading in OOP?
Ans. 
Operator overloading in OOP allows custom behavior for operators like +, -, *, etc.
• Operator overloading is a feature in OOP that allows defining custom behavior for operators

• Example: Overloading the + operator to concatenate strings or add two numbers

• Example: Overloading the * operator to perform matrix multiplication
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Q3. What is function overloading?
Ans. 
Function overloading is when multiple functions have the same name but different parameters or return types.
• Allows multiple functions with the same name but different parameters or return types

• Helps improve code readability and maintainability

• Example: int add(int a, int b) and float add(float a, float b)
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Q4. What are the differences between C and C++?
Ans. 
C is a procedural programming language while C++ is a multi-paradigm programming language with object-oriented features.
• C is a procedural programming language while C++ supports both procedural and object-oriented programming.

• C does not support classes and objects while C++ does.

• C does not have built-in support for exception handling while C++ does.

• C does not have namespaces while C++ does.

• C does not have function over
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Round duration - 45 minutes
Round difficulty - Easy

HR round that lasted for 45 minutes. Did brainstorming on puzzles and HR asked questions to know more about me.
Tips : During HR, think before you speak, they can catch any word that you speak. Prepare well for aptitude, as they shortlist less people after the test. Ask good questions during the end of the interviews. It might impress them. So prepare for it before going for the interview. Lastly, don’t be nervous, HRs are only trying to make you nervous during the interview as a part of the stress test.

Q1. How can you measure 45 minutes using two identical wires?
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Round duration - 60 minutes
Round difficulty - Medium

This was a 60 minute technical round where the interviewer asked programming based questions and questions on DBMS concepts.

Q1. 
Maximum of All Subarrays of Size k
Given an array of 'N' non-negative integers and an integer 'K', your task is to find the maximum elements for each subarray of size 'K'.
Input:
The first line contains...read more
Ans. 
Find the maximum elements for each subarray of size 'K' in an array of non-negative integers.
• Iterate through the array and maintain a deque to store the indices of elements in decreasing order.

• Pop elements from the deque if they are out of the current window of size 'K'.

• The front of the deque will always have the index of the maximum element in the current window.
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Q2. Can you explain the ACID properties in the context of database management systems?
Ans. 
ACID properties are a set of properties that guarantee the reliability of transactions in database management systems.
• Atomicity ensures that either all operations in a transaction are completed successfully or none of them are. For example, transferring money from one account to another should either be completed in full or not at all.

• Consistency ensures that the database remains in a consistent state before and after ...read more
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Q3. What is write-ahead logging in DBMS?
Ans. 
Write-ahead logging is a technique used in DBMS to ensure that changes are recorded in the log before they are applied to the database.
• Write-ahead logging ensures that changes are first written to the log file before being applied to the database to maintain data integrity.

• It helps in recovering the database in case of a system crash or failure by replaying the log entries to bring the database back to a consistent sta...read more
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Q4. What are the deadlock avoidance schemes?
Ans. 
Deadlock avoidance schemes are strategies used to prevent deadlocks in a system.
• Banker's algorithm: Ensures that the system will never enter an unsafe state by keeping track of available resources and only granting a request if it does not lead to a deadlock.

• Wait-die and Wound-wait: Two deadlock prevention schemes used in transaction processing systems to avoid deadlocks by allowing transactions to wait or abort based ...read more
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Q5. What is a clustered index?
Ans. 
A clustered index is a type of index that sorts and stores the data rows in the table based on their key values.
• Defines the order in which data is physically stored in a table

• Only one clustered index per table

• Helps in improving the performance of queries that involve range searches or sorting

• Example: Clustered index on a table's primary key
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Round duration - 60 minutes
Round difficulty - Easy

This was a 60 minute technical round where the interviewer asked data structure based questions, questions on OOPS and OS concepts.

Q1. What is a virtual function in C++?
Ans. 
A virtual function in C++ is a function that is declared within a base class and is redefined by a derived class.
• Virtual functions allow a function to be overridden in a derived class.

• They are used in polymorphism to achieve runtime binding.

• The base class function must be declared as virtual for dynamic binding to occur.

• Example: virtual void display() = 0; // pure virtual function
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Q2. Can you explain the malloc() and free() operations in the context of memory management in C?
Ans. 
malloc() is used to dynamically allocate memory in C, while free() is used to release allocated memory.
• malloc() allocates a block of memory of specified size and returns a pointer to the beginning of the block.

• free() deallocates the memory previously allocated by malloc() or calloc().

• Example: int *ptr = (int*)malloc(5 * sizeof(int)); // Allocates memory for 5 integers

• Example: free(ptr); // Deallocates the memory alloca
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Q3. What is structure padding?
Ans. 
Structure padding is the concept of adding empty bytes to a structure to align its data members on memory boundaries.
• Structure padding is done to optimize memory access and improve performance.

• Padding is necessary because most processors require data to be aligned on specific memory boundaries for efficient access.

• For example, if a structure contains a char followed by an int, padding may be added after the char to ali
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Round duration - 30 minutes
Round difficulty - Easy

HR based round that lasted for 30 minutes. The interviewer asked question to know more about me.

Round duration - 90 minutes
Round difficulty - Easy

Online test had 6 parts-psychometric test, aptitude, logical, English, computer skills and 2 coding questions. Time given to us was 90 minutes. Paper was quite lengthy and of average difficulty level. I was able to complete all the sections, but only one coding question.

Q1. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from the end to the beginning and append each character to a new string.

• Use built-in functions like reverse() or StringBuilder in languages like Python or Java for efficient reversal.

• Handle special characters and numbers while reversing the string.

• Ensure to consider the constraints provided in the problem statement.

• T...read more
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Round duration - 60 minutes
Round difficulty - Medium

Firstly the interviewer asked me to introduce myself after he introduced himself. Since i went there as experienced guy he asked me about my workings in the current company. After that,he asked some programming questions, tested my concepts of DBMS and OOPS, and some puzzles.

Q1. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal in a disconnected graph starting from vertex 0.
• Implement BFS algorithm to traverse the graph starting from vertex 0.

• Explore neighbor nodes first before moving to the next level neighbors.

• Consider the bidirectional nature of edges in an undirected graph.

• Output the BFS traversal sequence for each test case in a separate line.
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Q2. 
Prime Numbers Identification
Given a positive integer N, your task is to identify all prime numbers less than or equal to N.
Explanation:
A prime number is a natural number greater than 1 that has no po...read more
Ans. 
Identify all prime numbers less than or equal to a given positive integer N.
• Iterate from 2 to N and check if each number is prime

• Use the Sieve of Eratosthenes algorithm for efficient prime number identification

• Optimize by only checking up to the square root of N for divisors
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Q3. What is BCNF (Boyce-Codd Normal Form) in database management systems?
Ans. 
BCNF is a normal form in database management systems that ensures all determinants are candidate keys.
• BCNF stands for Boyce-Codd Normal Form.

• It is a stricter version of 3NF (Third Normal Form).

• In BCNF, every determinant must be a candidate key.

• It helps in reducing redundancy and anomalies in the database.

• Example: If a table has columns A, B, and C, and A determines B and B determines C, then it is not in BCNF unless A
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Q4. What is the difference between C and C++?
Ans. 
C is a procedural programming language while C++ is an object-oriented programming language with features like classes and inheritance.
• C is a procedural programming language, while C++ is a multi-paradigm language with support for object-oriented programming.

• C does not support classes and objects, while C++ does.

• C uses structures for data organization, while C++ uses classes.

• C does not have features like inheritance an...read more
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Q5. How can you make 3 cuts to divide a round cake into 8 equal pieces?
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Q6. How can you calculate 45 minutes using only 2 candles?
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Round duration - 60 minutes
Round difficulty - Easy

Again 2nd round started with an introduction from both sides. Then he started asking questions from resume itself. Working in the current company and all the projects that i have done. Few simple puzzles, OOPs concepts (with proper explanation and coding) and some database related questions(questions were easy you just need to brush up the basics). Some keywords related questions from C,C++,Java(usual questions like static ,final, abstract etc.). That was the 2nd round. Then I was called for the 3rd Round. Before 3rd round they also served tasty lunch.

Q1. 
Right View of Binary Tree
Given a binary tree of integers, your task is to output the right view of the tree.
The right view of a binary tree includes the nodes that are visible when the tree is observed...read more
Ans. 
The task is to output the right view of a binary tree, which includes the nodes visible when observed from the right.
• Traverse the tree level by level and keep track of the rightmost node at each level.

• Use a queue for level order traversal and a map to store the rightmost nodes.

• Print the values of the rightmost nodes stored in the map as the right view of the tree.
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Q2. You have 3 bulbs in one room and 3 switches in another room. The challenge is to determine which switch controls which bulb, with the constraint that you can only enter the bulb room once.
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Round duration - 45 minutes
Round difficulty - Easy

After that he asked me what I knew about SAP and there products(Please do read all about SAP and there products-not all but at least some famous products like ERP). Then he asked me one puzzle.

Q1. You have 2 eggs and a building with 100 floors. What is the minimum number of attempts needed to find the highest floor from which an egg can be dropped without breaking?
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Round duration - 45 minutes
Round difficulty - Easy

The round started with our Introduction to each other. After that interviewer asked me whether I do online shopping or not. I said yes then he asked me to design the online shopping portal using ER-Diagram . Then he asked me to create all the tables and populate it with data. Later on he asked me to normalize it. After all of this he asked me some simple puzzles and current salary and notice period. That was the 4th round.
After that I was asked to attend the final round and before 5th round they served snacks and tea to all of us.

Q1. Can you design an ER diagram for an online shopping portal?
Ans. 
Yes, I can design an ER diagram for an online shopping portal.
• Entities: User, Product, Order, Payment, Cart

• Relationships: User places Order, Order contains Product, Payment for Order, User has Cart

• Attributes: User (id, name, email), Product (id, name, price), Order (id, date), Payment (id, amount)
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