50+ Rakuten Interview Questions and Answers

Merge two sorted arrays into one sorted array in place.

• Iterate from the end of both arrays and compare elements to merge in place

• Use two pointers to keep track of the current position in each array

• Handle cases where one array is fully merged before the other

Reverse a stack using recursion without using any extra space other than the internal stack space.

• Use recursion to pop all elements from the original stack and store them in function call stack

• Once the stack is empty, push the elements back in reverse order using recursion

• Make use of auxiliary functions to handle the recursion process

JVM is a virtual machine that executes Java bytecode. Objects are created and managed in JVM memory using heap and stack.

• JVM stands for Java Virtual Machine

• It is responsible for executing Java bytecode

• Objects are created in JVM memory using heap and stack

• Heap is used for storing objects and stack is used for storing method calls

• Garbage collector is responsible for managing memory in JVM

A stack is a data structure that follows the Last-In-First-Out (LIFO) principle.

• Stack is a linear data structure

• Elements are added and removed from the same end called the top

• Common operations include push (add element) and pop (remove element)

• Stack can be implemented using arrays or linked lists

Polymorphism is the ability of an object to take on many forms. Overriding is when a subclass provides a specific implementation of a method that is already provided by its parent class.

• Polymorphism allows objects to be treated as if they are of any of their compatible types.

• Overriding is used to provide a specific implementation of a method that is already provided by its parent class.

• Example: Animal class has a method called makeSound(). Dog and Cat classes extend Animal an...read more

Objects in JVM memory are created on the heap and managed by the garbage collector.

• Objects are created on the heap memory in JVM.

• Memory for objects is allocated using the 'new' keyword.

• Objects are managed by the garbage collector to reclaim unused memory.

• Garbage collector uses different algorithms like Mark-Sweep, G1, etc.

• Example: 'String str = new String("Hello World");'

The coin change problem - given a set of coins and a target amount, find the minimum number of coins needed to make the change.

• Create an array to store the minimum number of coins needed for each amount from 0 to target

• Iterate through each coin and update the array for each amount that can be made using that coin

• Return the value at the target index of the array

Method overriding in Java allows a subclass to provide a specific implementation of a method that is already provided by its superclass.

• In method overriding, a subclass provides a specific implementation of a method that is already provided by its superclass.

• The method in the subclass must have the same name, return type, and parameters as the method in the superclass.

• Method overriding is used to achieve runtime polymorphism in Java.

• Example: class Animal { void sound() { Syst...read more

When a domain is entered in a browser, the browser goes through a series of steps to retrieve and display the website.

• Browser checks cache for DNS records to find IP address of the domain

• If not found, browser sends a DNS query to resolve the domain name to an IP address

• Browser establishes a TCP connection with the server hosting the website

• Browser sends an HTTP request to the server for the specific webpage

• Server processes the request and sends back an HTTP response with the ...read more

BookMyShow is an online platform for booking movie tickets and events. Here's the architecture design.

• The architecture should be scalable and flexible to handle high traffic during peak hours.

• The system should have multiple layers including presentation, application, and data storage.

• Use microservices architecture to break down the system into smaller, independent services.

• Implement caching mechanisms to improve performance and reduce load on the database.

• Use load balancers t...read more

JVM stands for Java Virtual Machine, which is a virtual machine that enables a computer to run Java programs.

• JVM is an abstract computing machine that enables a computer to run Java programs.

• It provides a runtime environment in which Java bytecode can be executed.

• JVM is platform-independent, meaning Java code can run on any device that has a JVM installed.

• It manages memory, provides security, and facilitates garbage collection.

• Examples of JVM implementations include Oracle Ho...read more

Peak and majority element finding algorithms

• Peak element: binary search for element greater than both neighbors

• Majority element: Boyer-Moore voting algorithm

• Boyer-Moore: iterate through array, count occurrences of each element, return element with count > n/2

Docker is a platform that allows you to package, distribute, and run applications in isolated containers.

• Docker is a tool designed to make it easier to create, deploy, and run applications by using containers.

• Containers allow a developer to package up an application with all parts it needs, such as libraries and other dependencies, and ship it all out as one package.

• Docker containers are lightweight and share the same operating system kernel, but run in isolation from each ot...read more

Calculate the sum of an array, treating negative numbers as positive, using recursion and without recursion.

• Create a variable to store the sum

• Iterate through the array and add each element to the sum, treating negative numbers as positive

• For the recursive solution, create a helper function that takes the array and the current index as parameters

• In the recursive function, check if the current index is within the array bounds

• If it is, add the element at the current index to the...read more

Polymorphism in Java allows objects of different classes to be treated as objects of a common superclass.

• Polymorphism is achieved through method overriding and method overloading.

• Method overriding allows a subclass to provide a specific implementation of a method that is already provided by its superclass.

• Method overloading allows multiple methods with the same name but different parameters in the same class.

• Polymorphism helps in achieving flexibility and reusability in code....read more

Designing large scale ML systems requires careful consideration of data, infrastructure, algorithms, and deployment.

• Identify the problem and define the objectives

• Collect and preprocess large amounts of data

• Choose appropriate algorithms and train models

• Deploy models on scalable infrastructure

• Monitor and evaluate performance regularly

• Continuously improve the system based on feedback

• Consider ethical and legal implications

• Collaborate with cross-functional teams

• Examples: Google's ...read more

Find and print the length of the longest subsequence from two given strings.

• Iterate through both strings and compare characters to find matching subsequences

• Use dynamic programming to keep track of longest common subsequence

• Return the length of the longest subsequence found

Architecture design for large scale app involves distributed systems, microservices, and scalability.

• Use distributed systems to handle large amounts of data and traffic

• Implement microservices to break down the app into smaller, manageable components

• Ensure scalability by designing for horizontal scaling and load balancing

• Use caching and database sharding to improve performance

• Implement fault tolerance and disaster recovery measures

• Consider using containerization and orchestrat...read more

Multithreading and multiprocessing are used to improve performance by executing multiple tasks simultaneously.

• Multithreading is useful for I/O-bound tasks, such as web scraping or file processing.

• Multiprocessing is useful for CPU-bound tasks, such as image processing or scientific computing.

• Both can be used together to achieve maximum performance.

• Care must be taken to avoid race conditions and deadlocks.

• Python's Global Interpreter Lock (GIL) limits the effectiveness of multit...read more

Implement a stack with push, pop, and getmin operations in O(1) time complexity.

• Use two stacks - one for storing the elements and the other for storing the minimum values

• When pushing an element, check if it is smaller than the current minimum and push it to the minimum stack if it is

• When popping an element, check if it is the current minimum and pop it from the minimum stack if it is

• To get the minimum element, simply return the top element of the minimum stack

The company offers a range of software products and solutions to clients in various industries.

• The company provides customized software solutions to meet the specific needs of each client.

• Products include CRM systems, data analytics tools, and project management software.

• Solutions may involve cloud-based services, mobile applications, and e-commerce platforms.

Sort an array of strings mixed with digits and numbers based on numbers.

• Extract numbers from each string using regex

• Convert extracted numbers to integers for comparison

• Sort the array based on the extracted numbers

Live coding to parse logs from a given file

• Choose a programming language

• Read the file line by line

• Use regular expressions to extract relevant information

• Store the extracted data in a structured format

Functional programming focuses on functions and immutability, while object-oriented programming focuses on objects and encapsulation.

• Functional programming uses pure functions and avoids side effects.

• Object-oriented programming uses classes and objects to model real-world entities.

• Functional programming emphasizes immutability, while object-oriented programming allows for mutable state.

• Functional programming languages include Haskell and Clojure, while object-oriented program...read more

Architecture for real scenarios involves designing systems that can handle real-world use cases and challenges.

• Consider scalability to handle increasing user load

• Ensure reliability and fault tolerance to prevent system failures

• Design for security to protect sensitive data

• Optimize performance for efficient operation

• Implement monitoring and logging for troubleshooting

• Use microservices architecture for flexibility and modularity

Print all subsets of an array of integers

• Use recursion to generate all possible subsets

• For each element, include or exclude it in the subset

• Base case: when all elements have been considered, print the subset

Designing a ride-hailing platform like Ola/Uber involves creating a user-friendly app, efficient routing algorithms, and a robust payment system.

• Developing a mobile app with an intuitive interface for users to book rides, track their driver, and make payments

• Implementing a dynamic pricing model based on demand and supply

• Designing efficient routing algorithms to minimize wait times and travel distances

• Building a reliable payment system that supports multiple payment options an...read more

To find the xpath of Flipkart product price, inspect the element and use the browser's developer tools.

• Open the Flipkart website and navigate to the product page

• Right-click on the price element and select 'Inspect' or press F12

• In the developer tools, locate the price element in the HTML code

• Right-click on the element in the HTML code and select 'Copy XPath'

• The XPath of the price element will be copied to your clipboard

Reverse a string without using toCharArray()

• Iterate through the string from the last character to the first

• Append each character to a new string

System design for big data application involves selecting appropriate technologies, designing data architecture, and ensuring scalability.

• Choose appropriate technologies for data storage, processing, and analysis

• Design data architecture that can handle large volumes of data

• Ensure scalability by using distributed systems and load balancing

• Consider security and privacy concerns

• Examples of technologies: Hadoop, Spark, NoSQL databases, distributed file systems

System design for use cases involves identifying requirements, designing components, and ensuring scalability and reliability.

• Identify use cases and requirements

• Design components to meet use case requirements

• Ensure scalability and reliability of the system

• Consider factors like performance, security, and maintainability

• Use tools like UML diagrams, flowcharts, and architecture diagrams

System design involves creating a high-level architecture for a software system to meet specific requirements.

• Identify the requirements and constraints of the system

• Break down the system into components and modules

• Define the interactions between components

• Consider scalability, reliability, and performance

• Choose appropriate technologies and tools

• Create a detailed design document

Architectural choices refer to the decisions made regarding the structure and design of a system.

• Architectural choices impact the scalability, performance, and maintainability of a system.

• Common architectural choices include monolithic, microservices, serverless, and event-driven architectures.

• Consider factors such as the size of the team, the complexity of the project, and the expected growth when making architectural decisions.

Use SQL query with WHERE clause to filter employees coming to office.

• Use SELECT statement to retrieve data from the database.

• Use WHERE clause to filter employees based on coming to office.

• Consider using a column in the database that indicates whether an employee is coming to office or not.

My design process involves understanding user needs, conducting research, creating prototypes, and iterating based on feedback.

• I start by conducting user research to understand their needs and pain points.

• I then create personas and user journey maps to visualize the user's experience.

• Next, I brainstorm and sketch out potential design solutions.

• I create wireframes and interactive prototypes to test and gather feedback.

• Based on the feedback, I iterate on the design, making impr...read more

My main language for programming is Java.

• I have been using Java for over 5 years.

• I am proficient in object-oriented programming with Java.

• I have experience in developing web applications using Java frameworks like Spring and Hibernate.

Pure components are React components that do not have any side effects and always render the same output for the same input.

• Pure components are typically implemented as functional components in React.

• They do not modify the state or props passed to them.

• Pure components help in optimizing performance by preventing unnecessary re-renders.

• Examples include functional components with no internal state or class components that extend PureComponent class.

Rakuten is a Japanese e-commerce company that offers a variety of services including online shopping, banking, and digital content.

• Founded in 1997 by Hiroshi Mikitani

• Offers a loyalty program called Rakuten Super Points

• Acquired Ebates, a cashback and shopping rewards platform, in 2014

Hash table is a data structure that maps keys to values using a hash function.

• Hash function maps keys to indices in an array

• Collisions can occur when two keys map to the same index

• Collision resolution techniques include chaining and open addressing

• Hash tables have O(1) average case time complexity for insert, delete, and search operations

Our project framework is based on the Page Object Model design pattern, using Selenium WebDriver and TestNG for automation testing.

• Page Object Model design pattern is used to create separate classes for each web page, making the code more organized and maintainable.

• Selenium WebDriver is used for interacting with web elements and performing actions on the web pages.

• TestNG is used for test case management, grouping, and reporting.

• We also use Maven for project management and dep...read more

TestNG is a testing framework used for automated testing in Java.

• TestNG allows for easy configuration of test cases using annotations.

• It supports parallel execution of test cases.

• TestNG provides reporting and logging features for test results.

• It allows for grouping of test cases for better organization.

• TestNG supports data-driven testing using data providers.

Python uses automatic memory management through garbage collection.

• Python uses reference counting to keep track of objects in memory.

• When an object's reference count reaches zero, it is deleted by the garbage collector.

• Python also uses a cyclic garbage collector to handle circular references.

• Memory can be managed manually using the 'gc' module.

• Python's memory management is efficient and transparent to the programmer.

System design for Uber involves creating a scalable and efficient platform for matching riders with drivers.

• Use microservices architecture for scalability and flexibility

• Implement geolocation services for real-time tracking

• Utilize algorithms for efficient matching of riders and drivers

• Include payment processing system for seamless transactions

Color theory is the study of how colors interact with each other and how they can be used to create effective designs.

• It involves understanding color wheel and color harmony

• It helps in creating a visual hierarchy and conveying emotions through colors

• It is important in branding and marketing

• Examples include complementary colors, analogous colors, and monochromatic colors

Generate all possible permutations of a given string

• Use recursion to generate permutations

• Swap characters to create different permutations

• Store permutations in an array of strings

Git is a distributed version control system while SVN is a centralized version control system.

• Git is distributed, meaning each user has a complete copy of the repository, while SVN is centralized, meaning there is a single repository.

• Git allows for offline work and branching and merging is easier, while SVN requires a network connection and branching and merging can be more complex.

• Git uses a SHA-1 hash to identify each commit, while SVN uses a revision number.

• Git has a more ...read more

Jenkins is a popular open-source automation server used for continuous integration and continuous delivery.

• Jenkins is installed on a server and can be accessed through a web interface.

• It allows automation of tasks like building, testing, and deploying software.

• Jobs in Jenkins are created to define the steps of the automation process.

• Plugins can be added to Jenkins to extend its functionality, such as integrating with version control systems.

• Jenkins can be configured to trigge...read more

Loop in a linked list

• Use Floyd's Cycle Detection Algorithm to detect a loop in a linked list

• Maintain two pointers, one moving at double the speed of the other

• If the two pointers meet at some point, there is a loop in the linked list

The architecture of a transformer refers to its physical design and components that allow for the transfer of electrical energy.

• Transformers consist of two coils of wire, known as the primary and secondary coils.

• The primary coil is connected to a power source, while the secondary coil is connected to the load.

• The core of the transformer is typically made of laminated iron to enhance magnetic flux.

• Transformers work on the principle of electromagnetic induction to transfer ener...read more