100+ Full Stack Developer Interview Questions and Answers for Freshers

Given a sorted alien dictionary in an array of strings, determine the character order of the alien language.

• Iterate through the words in the dictionary to build a graph of character dependencies.

• Perform a topological sort on the graph to determine the character order.

• Return the character array representing the order of characters in the alien language.

Determine the maximum profit that can be achieved by selling stocks with at most two transactions.

• Iterate through the array and calculate the maximum profit that can be achieved by selling stocks at each day.

• Keep track of the maximum profit after the first transaction and the maximum profit after the second transaction.

• Return the maximum profit that can be achieved overall.

The task is to determine the left view of a binary tree, which consists of nodes visible when viewed from the left side.

• Traverse the binary tree level by level from left to right, keeping track of the first node encountered at each level.

• Use a queue to perform level order traversal and keep track of the level number for each node.

• Store the first node encountered at each level in a result array to get the left view of the binary tree.

Find the smallest substring in a given string that contains all characters present in another string.

• Use a sliding window approach to find the smallest window in S that contains all characters in X

• Keep track of the characters in X using a hashmap

• Move the window by adjusting the start and end pointers

• Return the smallest window found

Determine the minimum length of instruction sequence for a robot to reach a given target on an infinite number line.

• Start at position 0 with speed +1, update position and speed based on 'A' and 'R' instructions

• For each test case, find the shortest sequence of instructions to reach the target

• Consider both positive and negative positions for the robot

• Return the minimum length of instruction sequence for each test case

The task is to determine if a given string of parentheses is balanced or not.

• Iterate through each character in the string and use a stack to keep track of opening parentheses

• If a closing parenthesis is encountered, check if it matches the top of the stack. If not, the string is not balanced

• If all parentheses are matched correctly and the stack is empty at the end, the string is balanced

The problem involves finding the number of ways to tile a 2xN board using 2x1 tiles.

• Use dynamic programming to solve the problem efficiently.

• Consider the base cases for N=1 and N=2 to build up the solution for larger N.

• Implement a recursive function with memoization to avoid redundant calculations.

• Keep track of the number of ways modulo 10^9 + 7 to handle large values of N.

• Test the solution with different values of N to ensure correctness.

Prisoners must devise a strategy to guess the color of their own hat based on the hats of others.

• Prisoners can agree on a strategy before the hats are assigned.

• One strategy is for each prisoner to count the number of hats of a certain color and use that information to guess their own hat color.

• Another strategy involves using parity to determine the color of their own hat.

• Prisoners can also use a signaling system to convey information about their hat color to others.

Mutex and Semaphore are synchronization mechanisms used in operating systems to control access to shared resources.

• Mutex is used to provide mutual exclusion, allowing only one thread to access a resource at a time.

• Semaphore is used to control access to a resource by multiple threads, with a specified number of permits available.

• Mutex is binary in nature (locked or unlocked), while Semaphore can have a count greater than 1.

• Example: Mutex can be used to protect critical section...read more

Yes, a singleton class is a class that can only have one instance created.

• Ensure the constructor is private to prevent external instantiation.

• Provide a static method to access the single instance.

• Use a static variable to hold the single instance.

• Example: class Singleton { private static Singleton instance = new Singleton(); private Singleton(){} public static Singleton getInstance() { return instance; }}

CPU scheduling algorithms determine the order in which processes are executed by the CPU.

• First Come First Serve (FCFS) - Processes are executed in the order they arrive.

• Shortest Job Next (SJN) - Process with the shortest burst time is executed next.

• Round Robin (RR) - Each process is given a small unit of time to execute in a cyclic manner.

• Priority Scheduling - Processes are executed based on priority levels assigned to them.

• Multi-Level Queue Scheduling - Processes are divided...read more

Abstract class is a class that cannot be instantiated, while an interface is a blueprint of a class with only abstract methods.

• Abstract class cannot be instantiated, but can have both abstract and non-abstract methods.

• Interface can only have abstract methods and cannot have method implementations.

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

• Method overriding is implementing a method in a subclass that is already p...read more

Function to return an Object using given Object and array of keys.

• Create a function that takes an Object and an array of keys as parameters.

• Iterate through the array of keys and check if each key exists in the Object.

• Create a new Object with the keys and corresponding values from the original Object.

Generate prime numbers between 10-30 and store in an array

• Iterate through numbers 10 to 30

• Check if each number is prime

• Store prime numbers in an array

React is a JavaScript library for building user interfaces, commonly used for creating interactive web applications.

• React is a front-end library developed by Facebook.

• It allows developers to create reusable UI components.

• React uses a virtual DOM to improve performance by only updating the necessary parts of the actual DOM.

• React can be used with JavaScript to create dynamic and interactive web applications.

• React components are written in JSX, a syntax extension for JavaScript.

To declare an array in JavaScript, use square brackets and separate elements with commas.

• Declare an array of strings: let myArray = ['apple', 'banana', 'orange'];

• Access elements by index: myArray[0] will return 'apple'.

• Add elements to the array: myArray.push('grape');

• Get the length of the array: myArray.length will return 4.

Schema defines the structure of a database, Indexes improve query performance, Event Loop manages asynchronous operations.

• Schema is a blueprint of a database that defines tables, columns, relationships, etc.

• Indexes are data structures that improve query performance by allowing faster data retrieval.

• Event Loop is a mechanism that manages asynchronous operations in JavaScript.

• Other important concepts for Full Stack Developers include REST APIs, MVC architecture, and version con...read more

Write a O(N) function to return the second largest number in an array in JavaScript.

• Iterate through the array and keep track of the largest and second largest numbers.

• Handle edge cases like when the array has less than 2 elements.

• Return the second largest number found.

A Full Stack Developer should possess a combination of technical skills, problem-solving abilities, and strong communication skills.

• Proficiency in both front-end and back-end technologies

• Strong understanding of databases and server-side languages

• Ability to work independently and in a team

• Good problem-solving skills and attention to detail

• Effective communication and collaboration with other team members

• Continuous learning and staying updated with new technologies

Yes, I enjoy working with data structures and algorithms.

• I find data structures and algorithms fascinating and enjoy solving problems using them.

• I have experience implementing various data structures like arrays, linked lists, stacks, queues, trees, and graphs.

• I am familiar with common algorithms such as sorting, searching, and graph traversal algorithms.

• I understand the importance of choosing the right data structure and algorithm for efficient and optimized solutions.

• I have...read more

Write a function to generate binary strings without consecutive 1's.

• Use dynamic programming to keep track of previous two states

• Start with base cases of 0 and 1

• For each new bit, check if adding it would create consecutive 1's

• If not, add it to the string and update the previous two states

• Repeat until desired length is reached

Stateful components store and manage state data, while stateless components do not store state data.

• Stateful components have internal state data that can change over time, while stateless components rely on props passed down from parent components.

• Stateful components are typically class components in React, while stateless components are functional components.

• Examples of stateful components include forms, modals, and sliders, while examples of stateless components include but...read more

Reactjs is preferred nowadays due to its component-based architecture, virtual DOM for efficient updates, and strong community support.

• Component-based architecture allows for reusability and easier maintenance of code.

• Virtual DOM enables efficient updates by only re-rendering components that have changed.

• Strong community support provides a wealth of resources, libraries, and tools for developers.

• React's declarative approach simplifies the process of building complex user inte...read more

Tags and attributes are essential components of HTML for structuring and styling web content.

• Tags are used to define different elements on a webpage, such as headings, paragraphs, images, etc.

• Attributes provide additional information about an element, like specifying its color, size, alignment, etc.

• Example: <h1> is a tag used for defining a top-level heading, and style='color: red;' is an attribute to change its color.

A round is a circular object or a series of actions that lead back to the starting point.

• A round can refer to a circular object, such as a ball or a wheel.

• In music, a round is a song where different groups start singing the same melody at different times, creating a harmonious effect.

• In sports, a round can refer to a single game or match in a tournament.

• In conversation, a round can refer to each person taking a turn to speak or share their thoughts.

• In programming, rounding is...read more

LRU cache is a data structure that stores recently used items and discards the least recently used item when the cache is full.

• LRU stands for Least Recently Used

• It is used to improve the performance of applications by reducing the number of disk reads or network calls

• It is commonly used in web browsers, databases, and operating systems

• It can be implemented using a hash table and a doubly linked list

• When an item is accessed, it is moved to the front of the list. When the cache...read more

Java is not 100% Object oriented because it supports primitive data types which are not objects.

• Java has primitive data types like int, float, boolean which are not objects.

• These primitive data types do not have methods or inheritance like objects.

• For example, int i = 5; does not have any methods associated with it.

Yes, async can be used without await.

• Async functions return a promise, which can be handled without using await.

• Using async without await can be useful for error handling or logging.

• However, it is important to handle the promise returned by the async function.

Removing duplicates without using inbuilt methods in JavaScript

• Create an empty array to store unique values

• Loop through the original array

• Check if the current element exists in the unique array

• If not, push it to the unique array

• Return the unique array

Database design for online course management system

• Create tables for courses, students, instructors, enrollments, and assignments

• Use relationships like one-to-many between courses and students, many-to-many between courses and instructors

• Include fields like course name, instructor name, student name, enrollment date, assignment details

• Consider using primary keys, foreign keys, and indexes for efficient data retrieval

Middleware is software that acts as a bridge between different applications or components, allowing them to communicate and share data.

• Middleware helps in integrating different systems and applications by providing a common platform for communication.

• It can handle tasks such as data transformation, security, logging, and error handling.

• Examples of middleware include web servers like Apache or Nginx, messaging systems like RabbitMQ, and API gateways like Kong.

The 40-30-30 rule in UI development refers to the ideal distribution of time spent on design, development, and testing.

• 40% of time should be spent on design, including wireframing, prototyping, and creating mockups

• 30% of time should be spent on development, implementing the design using code and programming languages

• 30% of time should be spent on testing, including unit testing, integration testing, and user acceptance testing

Eloquent is Laravel's ORM (Object Relational Mapping) that simplifies database operations.

• Eloquent provides an easy-to-use syntax for querying the database.

• It allows defining relationships between database tables.

• Eloquent supports soft deletes, eager loading, and more.

• Example: User::where('name', 'John')->first() retrieves the first user with name John.

Fundamental concepts in programming include variables, data types, control structures, functions, and algorithms.

• Variables store data for manipulation

• Data types define the kind of data that can be stored

• Control structures determine the flow of a program

• Functions are reusable blocks of code

• Algorithms are step-by-step procedures for solving problems

JPA is a specification for ORM in Java, while ORM is a technique for mapping objects to relational databases.

• JPA is a Java specification for ORM, while ORM is a technique for mapping objects to relational databases

• ORM is a general concept, while JPA is a specific implementation of ORM for Java

• JPA provides a set of interfaces and annotations for mapping Java objects to relational databases

• ORM frameworks like Hibernate, TopLink, and iBatis can be used with JPA

The current version of Java is Java 17.

• Java 17 was released on September 14, 2021.

• It is a long-term support (LTS) release.

• It introduced new features like sealed classes, pattern matching for switch statements, and more.

• Previous versions include Java 16, Java 15, and so on.

HTML, CSS, and JavaScript are the building blocks of web development.

• HTML (Hypertext Markup Language) is used for creating the structure of a webpage.

• CSS (Cascading Style Sheets) is used for styling the HTML elements.

• JavaScript is a programming language used for adding interactivity to web pages.

• Example: <html><head><style>body {color: blue;}</style></head><body><h1>Hello World!</h1><script>document.getElementById('demo').innerHTML = 'Hello JavaScript!';</script></body></html...read more

A promise in AngularJS is an object that represents the result of an asynchronous operation.

• Promises are used to handle asynchronous operations in AngularJS

• They are objects that represent the eventual completion or failure of an asynchronous operation and its resulting value

• Promises can be created using the $q service in AngularJS

• They have methods like then(), catch(), and finally() to handle the success, error, and completion of the promise

• Promises can be chained together to...read more

HTML and CSS are the building blocks of web development, with HTML providing the structure of a webpage and CSS styling its appearance.

• HTML stands for HyperText Markup Language and is used to create the structure of a webpage.

• CSS stands for Cascading Style Sheets and is used to style the appearance of a webpage.

• HTML uses tags to define elements like headings, paragraphs, images, and links.

• CSS allows for the customization of colors, fonts, layouts, and more on a webpage.

• Both H...read more

An IOC container is a software component that manages the dependencies between objects.

• IOC stands for Inversion of Control

• It is used to decouple the application components

• It creates and manages objects and their dependencies

• It allows for easy testing and maintenance of the application

• Examples of IOC containers include Spring, Unity, and Autofac

Company policies are guidelines and rules set by the company to govern the behavior and actions of employees.

• Company policies outline expectations for employee conduct

• They cover areas such as attendance, dress code, communication, and use of company resources

• Policies are typically documented in an employee handbook or on the company intranet

• Employees are expected to adhere to company policies to maintain a positive work environment

Truncate is a SQL command used to quickly delete all records from a table without logging individual row deletions.

• Truncate is faster than using DELETE statement as it does not log individual row deletions.

• Truncate resets the auto-increment value of the table.

• Truncate is a DDL (Data Definition Language) command and cannot be rolled back.

• Truncate does not activate triggers on the table.

• Example: TRUNCATE TABLE table_name;

jQuery is a fast, small, and feature-rich JavaScript library.

• jQuery simplifies HTML document traversing, event handling, and animating.

• It provides a simple API for AJAX requests and DOM manipulation.

• It is cross-platform and supports a wide range of browsers.

• It is open-source and has a large community of developers.

• Example: $('button').click(function(){ alert('Hello World!'); });

OOPs concepts are the fundamental principles of object-oriented programming.

• Encapsulation - binding data and functions together

• Inheritance - acquiring properties and behavior of parent class

• Polymorphism - ability to take multiple forms

• Abstraction - hiding implementation details

• Example: A car is an object that encapsulates data like speed and functions like accelerate and brake

• Example: A child class inherits properties and behavior from a parent class

• Example: A function can ta...read more

Create a form and log input value to console

• Create an HTML form element with input field

• Add an event listener to the form submit event

• Retrieve the input value using JavaScript

• Log the input value to console

Full stack refers to the development of both front-end and back-end portions of a web application.

• Full stack developers are proficient in both front-end and back-end technologies

• They can handle databases, servers, systems engineering, and clients

• Examples of full stack technologies include HTML, CSS, JavaScript, Node.js, React, and Angular

MVC pattern is a software design pattern used in Laravel to separate application logic from presentation.

• MVC stands for Model-View-Controller

• Model represents the data and business logic

• View represents the user interface

• Controller handles user requests and updates the model and view accordingly

• Laravel uses Blade templating engine for views

• MVC pattern helps in organizing code and making it more maintainable