100+ Saince Interview Questions and Answers

I worked as a data analyst, collecting, cleaning, and analyzing data to identify trends and make recommendations.

• Collected data from various sources such as databases, spreadsheets, and APIs

• Cleaned and organized data to ensure accuracy and consistency

• Performed statistical analysis to identify patterns and trends

• Created visualizations and reports to communicate findings to stakeholders

I am currently working on metrics such as first call resolution, average handling time, and customer satisfaction.

• First call resolution - ensuring that customer issues are resolved on the first call

• Average handling time - tracking the time it takes to resolve customer issues

• Customer satisfaction - measuring how satisfied customers are with the service provided

Chargeback is a process where a customer disputes a transaction and requests a refund from their bank.

• Chargeback occurs when a customer disputes a transaction and requests a refund from their bank.

• The bank then investigates the claim and may issue a chargeback to the merchant.

• The merchant can dispute the chargeback and provide evidence to support their case.

• If the chargeback is successful, the customer receives a refund and the merchant loses the sale and may incur additional...read more

Virtual functions are functions that can be overridden by derived classes. They are used for polymorphism and dynamic binding.

• Virtual functions are declared in a base class and can be overridden in derived classes

• They allow for polymorphism, where a pointer to a base class can call a function in a derived class

• Virtual functions use dynamic binding, where the function called is determined at runtime based on the object's type

• Virtual functions are used to implement abstract cla...read more

Common troubleshooting steps for VPN include checking network connectivity, verifying credentials, restarting VPN service, and updating software.

• Check network connectivity to ensure the VPN server is reachable

• Verify credentials to ensure correct username and password are being used

• Restart the VPN service on the client device or server

• Update VPN software to the latest version to fix any known issues

MongoDB is scalable due to its ability to horizontally partition data across multiple servers.

• MongoDB uses sharding to distribute data across multiple servers.

• Sharding allows for horizontal scaling by adding more servers to the cluster.

• MongoDB also supports replica sets for high availability and fault tolerance.

• Indexes can be created on any field in a MongoDB document, allowing for efficient querying of large datasets.

Design and implement a product management system with APIs and test cases

• Create a database schema to store product information

• Develop RESTful APIs for CRUD operations on products

• Implement authentication and authorization for API access

• Write unit tests and integration tests for APIs

• Use tools like Postman for API testing

Use 7 and 11 minute sand clocks to measure 15 minutes.

• Start both sand clocks simultaneously

• When the 7 minute clock runs out, flip it over

• When the 11 minute clock runs out, there will be 4 minutes left on the 7 minute clock

• When the 7 minute clock runs out again, a total of 15 minutes will have passed

To promote from a detractor, listen to their concerns, empathize with them, offer solutions, and follow up to ensure satisfaction.

• Listen actively to their complaints and concerns

• Empathize with their situation and show understanding

• Offer solutions to address their issues

• Follow up to ensure their satisfaction and resolve any remaining concerns

• Provide exceptional customer service to create a positive experience

SQL query to find the nth highest salary

• Use the ORDER BY clause to sort salaries in descending order

• Use the LIMIT and OFFSET clauses to skip the first n-1 highest salaries

• Combine the above steps in a single query to find the nth highest salary

Design a Cinema Ticket Reservation System

• Use a database to store movie information, showtimes, and seat availability

• Allow users to search for movies, select showtimes, and choose seats

• Implement a payment system for ticket purchases

• Send confirmation emails with QR codes for ticket validation

Documents required for onboarding a merchant include business registration documents, proof of identity, financial statements, and payment processing history.

• Business registration documents (e.g. business license, articles of incorporation)

• Proof of identity for the merchant (e.g. government-issued ID)

• Financial statements (e.g. bank statements, tax returns)

• Payment processing history (e.g. previous merchant account statements)

PayPal is an online payment system that allows individuals and businesses to transfer funds electronically.

• Allows users to make payments and money transfers online

• Offers a secure and convenient way to pay for goods and services

• Provides a platform for businesses to accept payments online

• Offers buyer and seller protection for eligible transactions

• Can be used to send and receive money internationally

Encryption of code involves converting plaintext into ciphertext to secure data.

• Choose a strong encryption algorithm like AES or RSA

• Generate a key for encryption

• Encrypt the plaintext using the key and algorithm

• Store or transmit the ciphertext securely

Joins are used to combine rows from two or more tables based on a related column between them. DML commands are used to manipulate data in a database.

• Joins are used in SQL to retrieve data from multiple tables based on a related column.

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• DML commands include INSERT, UPDATE, DELETE, and SELECT.

• INSERT is used to add new rows of data into a table.

• UPDATE is used to modify existing data in a table.

• DELETE ...read more

Use a max heap to efficiently find the nth maximum element in a data structure.

• Create a max heap from the given data structure.

• Pop the root element (maximum element) n times to find the nth maximum element.

• Time complexity is O(nlogn) for building the max heap and O(nlogn) for finding the nth maximum element.

Detecting loop in a linked list

• Use two pointers, one moving one node at a time and the other moving two nodes at a time

• If there is a loop, the two pointers will eventually meet

• If any of the pointers reach the end of the list, there is no loop

KYC stands for Know Your Customer and is a process of verifying the identity of clients. Enhanced Due Diligence is a more thorough investigation of high-risk clients.

• KYC is a regulatory requirement for financial institutions to prevent money laundering and terrorist financing

• It involves collecting and verifying customer information such as name, address, and identification documents

• EDD is a more in-depth investigation of high-risk clients, such as politically exposed persons ...read more

C++ is an extension of C with object-oriented programming features.

• C++ supports object-oriented programming while C does not.

• C++ has a richer set of libraries compared to C.

• C++ allows function overloading while C does not.

• C++ supports exception handling while C does not.

• C++ has a more complex syntax compared to C.

• C++ is backward compatible with C.

• C++ has a built-in string class while C does not.

Use subqueries to handle a situation in SQL without putting join condition

• Use subqueries to retrieve data from another table without explicitly joining them

• Subqueries can be used in SELECT, WHERE, or FROM clauses

• Example: SELECT * FROM table1 WHERE column1 IN (SELECT column2 FROM table2)

BFS (Breadth-First Search) is a graph traversal algorithm that explores all the vertices of a graph in breadth-first order.

• BFS starts at a given vertex and explores all its neighbors before moving to the next level of vertices.

• It uses a queue data structure to keep track of the vertices to be visited.

• BFS guarantees that it visits all the vertices of a connected graph.

• It can be used to find the shortest path between two vertices in an unweighted graph.

Use a hashmap to identify similar characters in a string.

• Create a hashmap to store character frequencies.

• Iterate through the string and update the frequencies in the hashmap.

• Identify characters with the same frequency as similar.

Virtual functions are functions in a base class that are overridden in derived classes to achieve runtime polymorphism.

• Virtual functions are declared in a base class with the 'virtual' keyword.

• They are overridden in derived classes using the 'override' keyword.

• They allow a function to be called based on the runtime type of an object.

• Virtual functions enable dynamic binding and late binding in C++.

• Example: virtual void display() = 0; in base class and void display() override {...read more

A hash map is a data structure that stores key-value pairs and uses a hash function to map keys to their corresponding values.

• Hash map uses a hash function to convert keys into array indices.

• Collisions can occur when two keys map to the same index, which can be resolved using techniques like chaining or open addressing.

• Hash maps have constant time complexity for insertion, deletion, and retrieval of key-value pairs.

• Examples of hash maps include Python's dict, Java's HashMap, ...read more

Memory allocation in C is done using functions like malloc, calloc, realloc and free.

• malloc function is used to allocate a block of memory of specified size

• calloc function is used to allocate a block of memory and initialize it to zero

• realloc function is used to change the size of previously allocated memory block

• free function is used to deallocate the memory previously allocated using malloc, calloc or realloc

• Memory allocation can also be done statically using arrays or dyna...read more

A virtual function is a function in a base class that is declared using the keyword 'virtual' and can be overridden by a function with the same signature in a derived class.

• Virtual functions allow for dynamic polymorphism in C++

• They are used in inheritance to achieve runtime polymorphism

• Example: virtual void display() = 0; in a base class and void display() override in a derived class

Merge sort is a divide-and-conquer algorithm that recursively divides an array into two halves, sorts them, and then merges them.

• Divide the array into two halves

• Recursively sort each half

• Merge the sorted halves back together

• Repeat until the entire array is sorted

The best complement I received from a customer was for my exceptional problem-solving skills and dedication to providing excellent service.

• Customer praised my quick response and resolution to their issue

• Customer appreciated my friendly and helpful attitude

• Customer mentioned my attention to detail and going above and beyond to assist them

PayPal offers a range of products including payment processing, money transfers, and online shopping tools.

• PayPal Checkout - allows customers to pay with PayPal, credit card, or debit card

• PayPal Credit - offers financing options for purchases

• Venmo - a mobile payment service owned by PayPal

• PayPal Here - a mobile card reader for in-person payments

• Xoom - a service for international money transfers

Repeat rate is the percentage of customers who return to make a purchase again.

• Repeat rate is a metric used to measure customer loyalty.

• It is calculated by dividing the number of repeat customers by the total number of customers.

• A high repeat rate indicates that customers are satisfied with the product or service.

• Repeat rate can be improved by providing excellent customer service and offering incentives for repeat purchases.

SQL query to find nth maximum element

• Use ORDER BY clause to sort the elements in descending order

• Use LIMIT to select the nth element

• Use subquery to exclude the first n-1 elements

DFS (Depth-First Search) is a graph traversal algorithm that explores as far as possible along each branch before backtracking.

• DFS uses a stack to keep track of visited nodes and explore adjacent nodes.

• It can be implemented recursively or iteratively.

• DFS is useful for solving problems like finding connected components, detecting cycles, and solving mazes.

LLD and class diagram for Minesweeper game

• Create classes for Board, Cell, Game, Player

• Use composition to represent relationships between classes

• Implement methods for revealing cells, flagging cells, checking for game over

• Consider using enums for cell states (covered, uncovered, flagged)

• Use UML notation to draw class diagram

Design a coffee machine with various functionalities like brewing different types of coffee, adding milk, and adjusting temperature.

• Include options for different types of coffee (espresso, latte, cappuccino)

• Allow users to add milk or cream to their coffee

• Provide options to adjust the temperature of the coffee

• Include a water reservoir for brewing coffee

• Add a display screen for user interaction

Customer service is the support and assistance provided to customers before, during, and after a purchase.

• Customer service involves addressing customer needs and concerns

• It includes providing information about products or services

• It also involves resolving customer complaints and issues

• Good customer service can lead to customer loyalty and repeat business

Customer service refers to the support and assistance provided to customers before, during, and after a purchase.

• Customer service involves addressing customer inquiries, concerns, and complaints in a timely and professional manner.

• It includes providing product information, troubleshooting issues, and ensuring customer satisfaction.

• Examples of customer service activities include answering phone calls, responding to emails, and resolving billing disputes.

• Customer service also i...read more

AML process involves identifying, assessing, and monitoring risks associated with money laundering.

• Customer Due Diligence (CDD) to verify customer identity and assess risk

• Transaction Monitoring to detect suspicious activity

• Reporting suspicious activity to authorities

• Ongoing monitoring of customer activity

• Risk-based approach to determine level of due diligence required

• Training employees on AML policies and procedures

Reverse a linked list in k sizes

• Break the linked list into groups of size k

• Reverse each group individually

• Connect the reversed groups back together

Use a SQL query to find the nth maximum value in a table.

• Use the ORDER BY clause to sort the values in descending order.

• Use the LIMIT clause to specify the nth maximum value.

• For example, to find the 3rd maximum value in a 'numbers' table: SELECT DISTINCT number FROM numbers ORDER BY number DESC LIMIT 2, 1;

I chose PayPal for its innovative technology and global reach, and customer support because I enjoy helping people and solving problems.

• PayPal offers cutting-edge technology and has a global presence, making it an exciting company to work for.

• I am passionate about providing excellent customer service and enjoy helping people resolve their issues.

• Customer support allows me to use my problem-solving skills and communication abilities to assist customers in a fast-paced environm...read more

Design a car rental system at a low level

• Use object-oriented programming to model cars, customers, rentals, etc.

• Implement a database to store information about available cars, customer bookings, etc.

• Include features like booking, returning, and searching for cars

• Consider implementing a pricing system based on factors like car type, duration of rental, etc.

malloc is a C function while new is a C++ operator for dynamic memory allocation.

• malloc allocates memory without initializing it while new initializes memory to zero

• malloc returns a void pointer while new returns a pointer to the object type

• malloc can only allocate memory while new can allocate memory and call the constructor

• malloc can be used in C and C++ while new can only be used in C++

Code for deleting a node in a linked list

• Create a temporary pointer to the node to be deleted

• Update the next pointer of the previous node to skip the node to be deleted

• Free the memory allocated to the node to be deleted

The task is to insert characters in between a given string.

• Create a function that takes a string and characters to insert

• Use string concatenation to insert characters at specified positions

• Return the modified string as an array of strings

Use SQL query to get daily count of transactions

• Use GROUP BY clause with the date column to group transactions by day

• Use COUNT function to count the number of transactions for each day

• Order the results by date to get a daily count of transactions

Projects in computer science involve developing software applications, algorithms, databases, and systems to solve various problems.

• Developing software applications for specific purposes

• Creating algorithms to optimize processes or solve complex problems

• Designing databases to store and manage large amounts of data

• Building systems to automate tasks or improve efficiency

Bubble sort is a simple sorting algorithm that repeatedly steps through the list, compares adjacent elements, and swaps them if they are in the wrong order.

• Start with the first element and compare it with the next element, swapping if necessary

• Repeat this process for each pair of adjacent elements in the array until the entire array is sorted

• Continue this process for each element in the array until no more swaps are needed

LRU cache with multi level caching involves implementing a cache with multiple levels of storage, where the least recently used items are evicted first.

• Implement a two-level cache system with a primary cache (e.g. in-memory) and a secondary cache (e.g. disk-based).

• Use a data structure like a doubly linked list and a hash map to efficiently manage the cache and track the least recently used items.

• When an item is accessed, move it to the front of the cache to mark it as the mos...read more

To find a loop in a linked list, we use Floyd's cycle-finding algorithm.

• Floyd's cycle-finding algorithm uses two pointers, one moving at a rate of one node per iteration and the other moving at a rate of two nodes per iteration.

• If there is a loop in the linked list, the two pointers will eventually meet at some node.

• To find the starting point of the loop, we reset one of the pointers to the head of the linked list and move both pointers at a rate of one node per iteration unt...read more

Rotten oranges problem involves finding the minimum time required to rot all oranges in a grid.

• Use Breadth First Search (BFS) to traverse the grid and update the ripening time of neighboring oranges.

• Keep track of the fresh oranges and the time taken to rot them all.

• Handle edge cases like no fresh oranges or unreachable oranges.

Design a system for managing a parking lot efficiently.

• Use a database to store information about available parking spots, vehicles, and payments.

• Implement a system for tracking entry and exit of vehicles.

• Include features like online booking, payment options, and real-time availability updates.

• Consider implementing a ticketing system for managing parking duration and fees.

The question involves writing React code in HackerRank.

• Understand the requirements of the task before starting to write the code.

• Use React components to create a user interface.

• Handle state management and user interactions using React hooks.

• Write clean and efficient code to solve the problem.

• Test the code thoroughly before submitting.

The expected value of fraud can be calculated by multiplying the probability of fraud occurrence with the potential loss from fraud.

• Calculate the probability of fraud occurrence based on historical data and industry trends

• Determine the potential loss from fraud by analyzing the impact on revenue, reputation, and legal costs

• Multiply the probability of fraud occurrence with the potential loss from fraud to get the expected value of fraud

Reverse the linked list in groups of k

• Iterate through the linked list in groups of k

• Reverse each group of k nodes

• Connect the reversed groups to form the final linked list

Design a parking lot system with working code.

• Create classes for ParkingLot, ParkingSpot, Vehicle, etc.

• Implement methods for parking, unparking, checking availability, etc.

• Use data structures like arrays, lists, or maps to manage parking spots.

• Consider different types of vehicles and parking spot sizes.

• Handle edge cases like full parking lot, invalid inputs, etc.

Stack and heap are memory management techniques used in computer programming.

• Stack is a region of memory where variables are stored and managed in a LIFO (Last-In-First-Out) order.

• Heap is a region of memory where dynamic memory allocation takes place.

• Stack memory is limited and fixed in size, while heap memory is larger and can grow dynamically.

• Stack memory is faster to access than heap memory.

• Examples of stack variables include function parameters and local variables, while ...read more

Calculate (a/b) + (c/d)

• Find the values of a, b, c, and d

• Divide a by b and c by d

• Add the results of the two divisions

The system design of a circuit breaker involves determining the appropriate rating, type, and coordination with other protective devices.

• Consider the voltage and current ratings to select the appropriate circuit breaker

• Choose between thermal-magnetic, magnetic, or electronic trip units based on the application

• Ensure proper coordination with upstream and downstream protective devices to prevent nuisance tripping

• Factor in environmental conditions and maintenance requirements wh...read more

An API (Application Programming Interface) is a set of rules and protocols that allows different software applications to communicate with each other.

• APIs define the methods for requesting and receiving data between software applications

• APIs can be used to access data from external sources, such as social media platforms or weather services

• Examples of APIs include the Twitter API, Google Maps API, and Spotify API

Java program on all data structures

• Start by implementing basic data structures like arrays, linked lists, stacks, queues, trees, and graphs

• Use Java built-in classes like ArrayList, LinkedList, Stack, Queue, TreeMap, and HashMap

• Practice implementing algorithms like sorting, searching, and traversal on these data structures

Money laundering is the illegal process of making large amounts of money generated by a criminal activity, such as drug trafficking or terrorist funding, appear to have come from a legitimate source.

• Money laundering involves disguising the origins of illegally obtained money.

• It typically involves a series of transactions to make the money appear legitimate.

• Money launderers often use complex financial transactions and shell companies to hide the source of the funds.

• Examples of...read more

GC collector in Java is responsible for managing memory by reclaiming unused objects and freeing up memory space.

• GC stands for Garbage Collector

• Automatically manages memory by reclaiming unused objects

• Prevents memory leaks and optimizes memory usage

• Different types of GC algorithms like Serial, Parallel, CMS, G1

• Example: System.gc() can be used to suggest garbage collection

KNN algorithm is a simple and effective machine learning algorithm for classification and regression tasks.

• KNN stands for K-Nearest Neighbors.

• It is a non-parametric, lazy learning algorithm.

• Works by finding the K closest training examples in feature space to a given input data point.

• Classification: Assign the most common class among the K nearest neighbors.

• Regression: Take the average of the K nearest neighbors' target values.

• Python libraries like scikit-learn provide impleme...read more

Design a search engine similar to Google

• Use web crawling to index websites

• Implement a ranking algorithm like PageRank

• Include features like autocomplete, spell check, and search suggestions

• Utilize machine learning for personalized search results

High-level design for a rental property website

• Use case analysis to identify key functionalities such as property listing, search, booking, payment

• Design a user-friendly interface with filters, maps, and photos for property listings

• Implement a secure payment gateway for online transactions

• Utilize a database to store property details, user information, and booking history

System design problems involve designing scalable and efficient software systems.

• Identify the requirements and constraints of the system

• Break down the system into smaller components

• Consider scalability, reliability, and performance

• Use appropriate data structures and algorithms

• Design for fault tolerance and load balancing

Design a notification service for sending alerts to users.

• Use a scalable messaging system like Kafka or RabbitMQ for handling notifications.

• Implement different types of notifications such as email, SMS, push notifications.

• Allow users to customize their notification preferences and frequency.

• Include features like scheduling notifications and tracking delivery status.

• Ensure security measures are in place to protect user data and prevent spamming.

Implementing an array list of strings

• Create a class to represent the array list

• Include methods to add, remove, and access elements in the array list

• Use an underlying array to store the elements

• Ensure the array list dynamically resizes when needed