Ernst & Young Interview Questions, Process, and Tips for Freshers

Round duration - 60 Minutes
Round difficulty - Medium

In this round, I was first asked a coding question related to Sliding Window Technique and then I was grilled on some major concepts from Java and Java Collections.

Q1. 
Smallest Subarray With K Distinct Elements
Given an array A consisting of N integers, your task is to find the smallest subarray of A that contains exactly K distinct integers.
If multiple such subarrays...read more
Ans. 
Find the smallest subarray in an array with exactly K distinct elements.
• Use a sliding window approach to keep track of the subarray with K distinct elements.

• Use a hashmap to store the frequency of each element in the window.

• Update the window by expanding or shrinking based on the number of distinct elements.

• Return the smallest subarray with K distinct elements and the smallest leftmost index.
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Q2. Why are Java Strings immutable in nature?
Ans. 
Java Strings are immutable to ensure thread safety, security, and optimization.
• Immutable strings prevent accidental changes, ensuring data integrity.

• String pooling allows for memory optimization by reusing common strings.

• Thread safety is guaranteed as strings cannot be modified concurrently.

• Security is enhanced as sensitive information cannot be altered once set.
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Q3. What do you know about the JIT compiler?
Ans. 
JIT compiler stands for Just-In-Time compiler, which compiles code during runtime for improved performance.
• JIT compiler translates bytecode into machine code at runtime

• It helps in optimizing performance by compiling frequently executed code

• Examples include Java HotSpot JIT compiler and .NET JIT compiler
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Q4. What is the difference between HashSet and HashMap in Java?
Ans. 
HashSet is a collection of unique elements, while HashMap is a key-value pair mapping.
• HashSet does not allow duplicate elements, HashMap allows duplicate keys but not values.

• HashSet uses a hash table to store elements, HashMap uses key-value pairs.

• Example: HashSet<String> set = new HashSet<>(); HashMap<String, Integer> map = new HashMap<>();
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Q5. Can you differentiate between ArrayList and Vector in Java?
Ans. 
ArrayList is non-synchronized and Vector is synchronized in Java.
• ArrayList is not synchronized, while Vector is synchronized.

• ArrayList is faster than Vector.

• Vector is thread-safe, while ArrayList is not.

• Example: ArrayList<String> list = new ArrayList<>(); Vector<String> vector = new Vector<>();
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Q6. Can you differentiate between HashMap and Hashtable?
Ans. 
HashMap and Hashtable are both data structures in Java used to store key-value pairs, but Hashtable is synchronized while HashMap is not.
• HashMap allows null values and one null key, while Hashtable does not allow null keys or values.

• HashMap is not synchronized and is not thread-safe, while Hashtable is synchronized and thread-safe.

• HashMap is faster than Hashtable for most operations, as it is not synchronized.

• HashMap i...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round started with some basic questions from Java 8 and then the interviewer started asking some questions from Spring Boot. At the end of the interview, I was also asked some questions from SQL and DBMS.

Q1. What are Java 8 streams?
Ans. 
Java 8 streams are a sequence of elements that support functional-style operations.
• Streams allow for processing sequences of elements in a functional way.

• They can be created from various data sources like collections, arrays, or I/O channels.

• Operations like filter, map, reduce, and collect can be performed on streams.

• Streams are lazy, meaning intermediate operations are only executed when a terminal operation is called...read more
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Q2. Write a Java 8 program to iterate through a Stream using the forEach method.
Ans. 
Java 8 program to iterate through a Stream using forEach method
• Create a Stream of elements using Stream.of() or any other method

• Use the forEach() method to iterate through the Stream and perform an action on each element

• Example: Stream.of(1, 2, 3, 4, 5).forEach(System.out::println);
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Q3. How does Spring Boot work?
Ans. 
Spring Boot is a framework that simplifies the development of Java applications by providing pre-configured settings and tools.
• Spring Boot eliminates the need for manual configuration by providing defaults for most settings.

• It includes embedded servers like Tomcat, Jetty, or Undertow, making it easy to run applications as standalone JAR files.

• Spring Boot also offers production-ready features like metrics, health checks...read more
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Q4. What is dependency injection?
Ans. 
Dependency injection is a design pattern in which components are given their dependencies rather than creating them internally.
• Dependency injection helps in achieving loose coupling between classes.

• It allows for easier testing by providing mock dependencies.

• There are three types of dependency injection: constructor injection, setter injection, and interface injection.
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Q5. Can you explain the @RestController annotation in Spring Boot?
Ans. 
The @RestController annotation in Spring Boot is used to define a class as a RESTful controller.
• Used to create RESTful web services in Spring Boot

• Combines @Controller and @ResponseBody annotations

• Eliminates the need for @ResponseBody annotation on each method

• Returns data directly in the response body as JSON or XML
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Q6. How does MVC work in Spring?
Ans. 
MVC in Spring is a design pattern that separates an application into three main components: Model, View, and Controller.
• Model represents the data and business logic of the application.

• View is responsible for rendering the user interface based on the data from the Model.

• Controller acts as an intermediary between Model and View, handling user input and updating the Model accordingly.

• Spring MVC provides annotations like @...read more
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Q7. What are a few features of Spring Boot?
Ans. 
Spring Boot is a framework that simplifies the development of Java applications by providing pre-configured setups.
• Auto-configuration: Spring Boot automatically configures the application based on dependencies added to the project.

• Embedded server: Spring Boot comes with an embedded Tomcat, Jetty, or Undertow server for easy deployment.

• Actuator: Provides production-ready features like monitoring, metrics, and health che
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Round duration - 30 Minutes
Round difficulty - Easy

This was a Technical Cum HR round where I was first asked some basic Java related concepts and then we discussed
about my expectations from the company , learnings and growth in the forthcomig years. I would suggest be honest and
try to communicate your thoughts properly in these type of rounds to maximise your chances of getting selected.

Moderate difficulty level

Was asked to talk about general topic

Q1. Basic excel questions
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Round duration - 60 Minutes
Round difficulty - Medium

This was a preety intense round revolving mainly around the core concepts of JavaScript . I was confident about my
skills in JavaScript as I already had some projects in JS and I also completed the Guided Path of JS in CodeStudio
which boosted my preparation and helped me crack these Frontend Interviews.

Q1. What are callbacks in JavaScript?
Ans. 
Callbacks in JavaScript are functions passed as arguments to other functions to be executed later.
• Callbacks are commonly used in event handling, asynchronous programming, and functional programming.

• They allow for functions to be executed after another function has finished its execution.

• Example: setTimeout(callbackFunction, 1000) will execute callbackFunction after 1 second.
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Q2. Can you explain hoisting in JavaScript?
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope.
• Variable declarations are hoisted to the top of their scope but not their assignments.

• Function declarations are fully hoisted, meaning they can be called before they are declared.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q3. What are closures in JavaScript?
Ans. 
Closures in JavaScript are functions that have access to variables from their outer scope even after the outer function has finished executing.
• Closures allow functions to access variables from their parent function's scope

• They maintain a reference to the variables they need, even after the parent function has finished executing

• Closures are commonly used to create private variables and data encapsulation in JavaScript

• Ex...read more
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Q4. What is the difference between slice and splice in JavaScript?
Ans. 
slice() returns a shallow copy of a portion of an array without modifying the original array, while splice() changes the contents of an array by removing or replacing existing elements.
• slice() does not modify the original array, while splice() does

• slice() returns a new array, while splice() returns the removed elements

• slice() takes start and end index as arguments, while splice() takes start index, number of elements t...read more
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Q5. What is a first-class function in JavaScript?
Ans. 
A first-class function in JavaScript is a function that can be treated like any other variable.
• Can be passed as an argument to other functions

• Can be returned from other functions

• Can be assigned to variables

• Can be stored in data structures
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Q6. How would you sort an array of integers in JavaScript?
Ans. 
Use the built-in sort() method to sort an array of integers in JavaScript.
• Use the sort() method with a compare function to sort the array in ascending order.

• For descending order, modify the compare function to return b - a instead of a - b.

• Example: const numbers = [4, 2, 5, 1, 3]; numbers.sort((a, b) => a - b);
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Q7. 
Covid Vaccination Distribution Problem
As the Government ramps up vaccination drives to combat the second wave of Covid-19, you are tasked with helping plan an effective vaccination schedule. Your goal is...read more
Ans. 
Maximize the number of vaccines administered on a specific day while adhering to certain rules.
• Given n days, maxVaccines available, and a specific dayNumber, distribute vaccines to maximize on dayNumber

• Administer positive number of vaccines each day with a difference of 1 between consecutive days

• Ensure sum of vaccines distributed does not exceed maxVaccines

• Output the maximum number of vaccines administered on dayNumber
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Round duration - 60 Minutes
Round difficulty - Medium

In this round, I was asked questions from React and Redux. Since I already had prior experience in working with React
and Redux , I answered most of the questions correctly and was preety much confident about passing this round.

Q1. What are the differences between a class component and a functional component in ReactJS?
Ans. 
Class components are ES6 classes that extend from React.Component and have access to state and lifecycle methods, while functional components are simple functions that take props as arguments and return JSX.
• Class components are defined using ES6 classes and extend from React.Component

• Functional components are simple functions that take props as arguments and return JSX

• Class components have access to state and lifecycle...read more
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Q2. What are the differences between stateless and stateful components in ReactJS?
Ans. 
Stateless components do not have internal state, while stateful components have internal state.
• Stateless components are functional components that do not have internal state.

• Stateful components are class components that have internal state.

• Stateless components are simpler and easier to test.

• Stateful components are more complex and can hold and update internal state.

• Example: Stateless component - const Button = () =>...read more
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Q3. What is the diffing algorithm in ReactJS?
Ans. 
React uses a diffing algorithm called Virtual DOM to efficiently update the actual DOM based on changes in state or props.
• Virtual DOM is a lightweight copy of the actual DOM.

• React compares the Virtual DOM with the previous Virtual DOM to identify the minimal number of changes needed to update the actual DOM.

• This process is known as reconciliation and helps in optimizing performance by reducing unnecessary re-renders.

• Ex...read more
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Q4. What is reconciliation in ReactJS?
Ans. 
Reconciliation in ReactJS is the process of updating the DOM to match the virtual DOM after a component's state or props have changed.
• Reconciliation is the algorithm React uses to update the UI efficiently.

• It compares the virtual DOM with the actual DOM and only updates the parts that have changed.

• Reconciliation is a key feature that helps React achieve high performance.

• Example: When a user interacts with a React compo...read more
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Q5. What are props in React?
Ans. 
Props in React are used to pass data from a parent component to a child component.
• Props are read-only and cannot be modified by the child component.

• Props are passed down the component tree.

• Props can be any type of data, such as strings, numbers, objects, or functions.

• Example: <ChildComponent name='John' age={25} />
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Q6. What are the advantages of using Redux?
Ans. 
Redux helps manage application state in a predictable way.
• Centralized state management

• Predictable state changes with actions and reducers

• Time-travel debugging with Redux DevTools

• Ecosystem of middleware for additional functionality
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Q7. What are the key differences between mapStateToProps() and mapDispatchToProps() in Redux?
Ans. 
mapStateToProps() is used to access the Redux state in a component, while mapDispatchToProps() is used to dispatch actions to update the state.
• mapStateToProps() is used to access the Redux state and return data as props for a component.

• mapDispatchToProps() is used to dispatch actions to update the Redux state.

• mapStateToProps() is a function that takes the current state as an argument and returns an object with props th...read more
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Q8. What is the Combine Reducer in Redux?
Ans. 
Combine Reducer is a function in Redux that combines multiple reducers into a single reducer function.
• Combines multiple reducers into a single reducer function

• Helps manage different pieces of state in Redux store

• Improves code organization and maintainability

• Example: combineReducers({ reducer1, reducer2 })

• Example: const rootReducer = combineReducers({ reducer1, reducer2 })
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Q9. How is Relay different from Redux?
Ans. 
Relay is a GraphQL client specifically designed for React, while Redux is a state management library for any JavaScript application.
• Relay is tightly integrated with GraphQL, making it easier to fetch and manage data from a GraphQL server.

• Redux is a more general-purpose state management library that can be used with any backend technology.

• Relay uses a declarative approach to data fetching, where components declare their...read more
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Q10. How can we structure the top-level directories in Redux?
Ans. 
Top-level directories in Redux should be structured based on functionality and feature modules.
• Separate directories for actions, reducers, and components

• Group related functionality together in separate directories

• Use feature modules to encapsulate related actions, reducers, and components

• Example: 'actions', 'reducers', 'components', 'utils', 'constants'
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Round duration - 30 Minutes
Round difficulty - Easy

This was a Technical Cum HR round where I was first asked some basic principles around Frontend Web Development
and then we discussed about my expectations from the company , learnings and growth in the forthcomig years. I would
suggest be honest and try to communicate your thoughts properly in these type of rounds to maximise your chances of
getting selected.

Q1. What do you know about the company?
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Q2. Why should we hire you?
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Q1. Why do you want to join us?
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Q1. RPA related questions
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Case Study on HR. Real-life example based.

Q1. Diversity in organization
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Q2. Explain your professional journey
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Q1. What do you use the separate lines in standard output in c++?
Ans. 
Separate lines in standard output in C++ are used to display different pieces of information on separate lines for better readability.
• Separate lines are used to display different outputs or messages in a clear and organized manner.

• They are commonly used with the 'endl' or ' ' characters to move to the next line.

• For example, cout << 'Hello' << endl; will display 'Hello' on one line and move to the next line for the next
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Q2. How do double linked list work? What is the difference between linked list and double linked list?
Ans. 
A double linked list is a data structure where each node contains a reference to the previous and next node.
• In a linked list, each node contains a reference to the next node only, while in a double linked list, each node contains references to both the previous and next nodes.

• Double linked lists allow for traversal in both directions, making operations like deletion and insertion easier compared to single linked lists.

• ...read more
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