700+ Full Stack Developer Interview Questions and Answers

Calculate the total amount of rainwater that can be trapped between given elevations in an array.

• Iterate through the array and calculate the maximum height on the left and right of each bar.

• Calculate the amount of water that can be trapped at each bar by taking the minimum of the maximum heights on the left and right.

• Sum up the trapped water at each bar to get the total trapped water for the entire array.

Identify all distinct triplets within an array that sum up to a specified number.

• Iterate through the array and use nested loops to find all possible triplets.

• Check if the sum of the triplet equals the specified number.

• Print the valid triplets or return -1 if no triplet exists.

Check if a given string is a palindrome considering only alphanumeric characters.

• Remove non-alphanumeric characters from the input string.

• Compare the string with its reverse to check for palindrome.

• Handle edge cases like empty string or single character input.

To maximize the number of balloons burst with an arrow, target the balloons with the most adjacent balloons.

• Identify clusters of balloons that are adjacent to each other.

• Target the balloons in the clusters with the most adjacent balloons to burst the maximum number.

• Consider the position and size of the clusters to strategically burst the balloons.

Determine if a robot's movement path is circular on a 2D grid based on a given sequence of moves.

• Iterate through the sequence of moves and keep track of the robot's position and direction.

• Check if the robot returns to the starting position after completing the moves.

• Use a counter-clockwise rotation (L) and clockwise rotation (R) to update the direction of the robot.

• Use 'G' to move the robot one unit in the current direction.

Check if a string contains any permutation of another string as a substring.

• Iterate through str2 with a sliding window of length str1, check if any permutation of str1 is present.

• Use a hashmap to store the frequency of characters in str1 and str2 for comparison.

• If the frequencies of characters in the sliding window match the frequencies of characters in str1, return True.

Find all possible paths for a rat in a maze from start to finish, moving in 'U', 'D', 'L', 'R' directions.

• Use backtracking to explore all possible paths in the maze.

• Keep track of visited cells to avoid loops.

• Recursively try moving in all directions and backtrack when reaching dead ends.

• Return the valid paths in alphabetical order as an array of strings.

Account Statements Transcription is a full stack application for converting Excel sheets to SQL tables, fetching data in UI, and allowing downloads in various formats.

• Create a front-end interface for users to upload Excel sheets

• Develop a back-end system to convert Excel data into SQL tables

• Implement a query system to fetch data based on user needs in the UI

• Provide options for users to download data in Excel or Word formats

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.

Implement Selection Sort algorithm to sort an array of non-negative integers in non-decreasing order.

• Iterate through the array and find the minimum element in the unsorted part.

• Swap the minimum element with the first element of the unsorted part.

• Repeat the process for the remaining unsorted part until the array is sorted.

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

Group anagrams in an array of strings based on their characters.

• Iterate through each string in the input array

• Sort the characters of each string and use the sorted string as a key in a hashmap to group anagrams

• Return the values of the hashmap as the grouped anagrams

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

Convert a binary tree into a sum tree by replacing each node's value with the sum of its children's values. Return the preorder traversal of the sum tree.

• Traverse the tree in a bottom-up manner to calculate the sum of children for each node.

• Set leaf nodes to 0 and update non-leaf nodes with the sum of their children.

• Return the preorder traversal of the modified tree.

Business logic, presentation logic, and service logic can be separated using Angular's component architecture.

• Create separate components for each logic layer

• Use services to handle business logic

• Use pipes for presentation logic

• Keep components simple and focused on one task

• Use dependency injection to share services between components

To ensure computer network security, implement firewalls, use strong passwords, regularly update software, and conduct security audits.

• Install and configure firewalls to monitor and control incoming and outgoing network traffic.

• Use strong passwords and two-factor authentication to prevent unauthorized access.

• Regularly update software and operating systems to patch vulnerabilities.

• Conduct regular security audits to identify and address potential security threats.

• Implement netw...read more

Calculate minimum time to travel from source to destination using direct movement and wormholes.

• Calculate the time to move directly from source to destination using |dx - sx| + |dy - sy| formula.

• Check if using any wormhole reduces the total travel time.

• Consider all possible combinations of direct movement and wormhole usage to find the minimum time.

Develop a function to remove all instances of a given character from a string.

• Create a function that takes the input string and character to be removed as parameters.

• Iterate through each character in the input string and only add characters that are not equal to the given character to a new string.

• Return the new string as the output.

• Handle edge cases such as empty input string or character.

• Example: Input string 'hello world' and character 'o' should return 'hell wrld'.

Clustered index determines the physical order of data in a table, while non-clustered index has a separate structure.

• Clustered index determines the physical order of data in a table

• Non-clustered index has a separate structure that includes a copy of the indexed columns and a pointer to the actual data

• A table can have only one clustered index, but multiple non-clustered indexes

• Clustered index is faster for retrieving large ranges of data, while non-clustered index is faster fo...read more

Git pull combines git fetch and git merge, while git fetch only downloads new data from a remote repository.

• Git pull is used to update the local branch with the latest changes from the remote repository.

• Git fetch only downloads new data from the remote repository, but does not integrate it into the local branch.

• Git pull is a combination of git fetch and git merge commands.

• Git fetch is useful to see what changes have been made in the remote repository before merging them into ...read more

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

Different methods of session management in Servlet

• Cookies

• URL Rewriting

• Hidden Form Fields

• Session Tracking API

• HTTP Session

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.

Optimize website assets loading by minimizing file sizes, leveraging caching, and using asynchronous loading.

• Minimize file sizes by compressing images, minifying CSS and JavaScript files

• Leverage caching by setting appropriate cache headers and using a content delivery network (CDN)

• Use asynchronous loading techniques such as lazy loading, deferred loading, and async/defer attributes

• Combine and bundle multiple files to reduce the number of requests

• Optimize the order of loading ...read more

New tags in Media Elements in HTML5 include <audio> and <video>.

• <audio> tag for audio content

• <video> tag for video content

• Attributes like controls, autoplay, loop, etc. can be used with these tags

Multithreading allows multiple threads to run concurrently, while semaphores are used to control access to shared resources in a synchronized manner.

• Multithreading involves running multiple threads within a single process, allowing for parallel execution of tasks.

• Semaphores are used to control access to shared resources by allowing only a certain number of threads to access the resource at a time.

• Semaphores can be binary (mutex) or counting, with binary semaphores used for mu...read more

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.

Spring Boot is a framework that simplifies the development of Java applications by providing default configurations and dependencies.

• Spring Boot eliminates the need for manual configuration by providing sensible defaults.

• It uses an embedded server, such as Tomcat or Jetty, to run the application.

• Spring Boot automatically configures the application based on the dependencies added to the project.

• It promotes convention over configuration, reducing boilerplate code.

• Spring Boot su...read more

Web services offer advantages such as interoperability, scalability, reusability, and platform independence.

• Interoperability: Web services allow different applications to communicate and share data regardless of the programming languages or platforms they are built on.

• Scalability: Web services can handle a large number of requests and can be easily scaled up or down to meet changing demands.

• Reusability: Web services promote code reuse as they can be accessed by multiple appli...read more

CORS in MVC is Cross-Origin Resource Sharing, a mechanism that allows restricted resources on a web page to be requested from another domain.

• CORS is a security feature implemented in web browsers to prevent cross-origin requests by default.

• It works by adding specific HTTP headers to the server's response, indicating which origins are allowed to access the resources.

• In MVC, CORS can be configured using the 'EnableCors' attribute on controllers or by configuring it in the 'Web....read more

My strength is problem-solving and my weakness is public speaking.

• Strength: Proficient in identifying and solving complex problems

• Weakness: Nervousness while speaking in front of large audiences

• Strength: Ability to learn and adapt to new technologies quickly

• Weakness: Difficulty in delegating tasks to others

• Strength: Attention to detail and ability to work under pressure

• Weakness: Tendency to overthink and second-guess decisions

package.json is a file used in Node.js projects to manage dependencies and scripts.

• Contains metadata about the project

• Lists dependencies and devDependencies

• Scripts for running tasks

• Version of Node.js required

• Author and license information

I was asked to solve MongoDB queries and determine the best way to execute them.

• I was asked to write queries to retrieve specific data from MongoDB collections.

• I used aggregation pipelines to perform complex queries involving multiple stages.

• I optimized queries by creating indexes on frequently accessed fields.

• I utilized MongoDB's query optimizer to analyze and improve query performance.

• I used explain() method to understand query execution plans and make necessary adjustments...read more

I research, ask for help, and try different approaches until I find a solution.

• I start by researching the issue thoroughly, looking for similar problems and solutions online.

• If that doesn't work, I ask for help from colleagues or online communities.

• I also try different approaches and solutions until I find one that works.

• If all else fails, I escalate the issue to a higher authority or seek additional resources.

• I document the issue and solution for future reference.

OOPs is Object-Oriented Programming. It is implemented differently in Functional Programming and Traditional Programming.

• OOPs is a programming paradigm that focuses on objects and their interactions.

• In Traditional Programming, OOPs is implemented using classes, objects, and inheritance.

• In Functional Programming, OOPs is implemented using higher-order functions and immutable data.

• Functional Programming emphasizes pure functions and avoids mutable state.

• In Traditional Programmi...read more

Python compiles source code to bytecode for faster execution, stored in .pyc files.

• Python interpreter compiles source code to bytecode before execution

• Bytecode is platform-independent and faster to execute than source code

• Compiled bytecode is stored in .pyc files for future use and faster startup time

• If source code is modified, .pyc files are automatically recompiled

A Java 8 program to iterate a Stream using the forEach method.

• Create a Stream object from a collection or array

• Use the forEach method to perform an action on each element of the Stream

• The action can be a lambda expression or a method reference

Dependency Injection is a design pattern where the dependencies of a class are provided externally rather than being created within the class itself.

• Dependency Injection helps in achieving loose coupling between classes.

• It allows for easier testing and maintenance of code.

• In Spring Boot, dependencies are injected using annotations like @Autowired.

• Example: In a Spring Boot application, if a class requires a database connection, the connection object can be injected into the cl...read more

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

Java 8 streams are a sequence of elements that can be processed in parallel or sequentially.

• Streams provide a functional programming approach to process collections in Java.

• They allow for concise and expressive code.

• Streams can be used to filter, map, reduce, and perform other operations on data.

• Example: List numbers = Arrays.asList(1, 2, 3, 4, 5); numbers.stream().filter(n -> n % 2 == 0).forEach(System.out::println);

• This example filters even numbers from the list and prints ...read more

SQL injection is a web security vulnerability that allows an attacker to manipulate a database query to execute unauthorized actions.

• SQL injection occurs when user-supplied data is not properly validated or sanitized before being used in an SQL query.

• Attackers can exploit this vulnerability to bypass authentication, retrieve sensitive data, modify or delete data, or even execute arbitrary commands.

• To prevent SQL injection, use parameterized queries or prepared statements, inp...read more

One-on-one round refers to a meeting or interview between two individuals.

• It is a private conversation between two people.

• It is usually conducted to discuss a specific topic or issue.

• It can be a part of a larger group interview process.

• Examples include job interviews, performance evaluations, and coaching sessions.

Classes needed to create a GET REST API

• Controller class to handle the request

• Service class to perform business logic

• Repository class to interact with database

• Model class to define data structure

• RequestMapping annotation to map the URL

Data can be fetched using APIs and passed to the view using templating engines or front-end frameworks.

• Use AJAX calls to fetch data from the backend APIs

• Parse the data received in JSON format

• Use templating engines like Handlebars or front-end frameworks like React to pass the data to the view

• Render the data dynamically on the view

Various MongoDB queries were asked based on the scraped data.

• Filtering documents based on specific criteria

• Sorting documents in ascending or descending order

• Performing aggregation operations like grouping and counting

MVC components include Model, View, and Controller. Model represents data and business logic, View displays the data, and Controller handles user input and updates the Model and View.

• Model: Represents data and business logic

• View: Displays the data to the user

• Controller: Handles user input and updates the Model and View