60+ Full Stack Engineer Interview Questions and Answers

Generate all possible non-empty subsets of a given array of distinct integers.

• Use recursion to generate all subsets by including or excluding each element in the array.

• Maintain a current subset and iterate through the array to generate subsets.

• Print each subset as it is generated to get all possible non-empty subsets.

The task is to find the length of the longest palindromic subsequence in a given string.

• Iterate through the string and create a 2D array to store the lengths of palindromic subsequences.

• Use dynamic programming to fill the array based on the characters in the string.

• Consider the cases where characters match or do not match to update the array values.

• Return the length of the longest palindromic subsequence for each test case.

Check if two strings follow the same pattern based on bijection between letters and words.

• Iterate through each letter in T and corresponding word in S to create a mapping.

• Use a hashmap to store the mapping between letters and words.

• Check if the mapping is consistent for all test cases.

Reverse a singly linked list of integers and return the head of the reversed linked list.

• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Keep track of the current, previous, and next nodes while traversing the linked list.

• Update the head of the reversed linked list to be the last node encountered.

• Ensure to handle edge cases like an empty linked list or a single node in the list.

Implement a function to return the level order traversal of a binary tree of integers.

• Create a queue to store nodes for level order traversal

• Start with the root node and enqueue it

• While the queue is not empty, dequeue a node, print its value, and enqueue its children

• Repeat until all nodes are traversed

Count the number of subarrays in an array whose sum is divisible by a given integer K.

• Iterate through the array and keep track of the running sum modulo K.

• Use a hashmap to store the frequency of remainders.

• For each prefix sum, check how many previous prefix sums have the same remainder.

• Return the total count of subarrays with sum divisible by K.

Return an array where each element represents the count of smaller elements on its right side in the given array.

• Iterate through the array from right to left and maintain a sorted list of elements encountered so far.

• For each element, find its index in the sorted list to determine the count of smaller elements on its right side.

• Use binary search or segment trees for efficient searching and updating of the sorted list.

Given a linked list of ninja villages, find the next greater ninja strength in the nearest linked village.

• Traverse the linked list and store the elements in an array.

• Use a stack to keep track of elements with no next greater element found yet.

• Iterate through the array to find the next greater element for each village.

• Return the array of next greater elements for each village.

The task is to find the maximum size of a submatrix consisting of all 1's in a given binary-valued matrix.

• Iterate through each cell of the matrix

• For each cell, calculate the maximum size of a submatrix with that cell as the top-left corner

• Keep track of the maximum size encountered so far

• Return the maximum size

The minimum number of operations required to make all elements of the given array equal.

• The array is generated based on the formula ARR[i] = (2*i + 1).

• To equalize the array, increment one element and decrement another in each operation.

• The number of operations needed is equal to the difference between the maximum and minimum elements in the array.

The 0/1 Knapsack Problem involves maximizing the total value of items a thief can steal within a given weight limit.

• Dynamic programming can be used to solve this problem efficiently.

• Create a 2D array to store the maximum value that can be stolen at each weight capacity.

• Iterate through the items and update the array based on whether the item is included or not.

• The final answer will be the value at the last cell of the array.

Implement a function to count the number of distinct substrings in a given string using a trie data structure.

• Create a trie data structure to store the substrings of the input string.

• Traverse the trie to count the number of distinct substrings.

• Handle empty string as a distinct substring.

• Return the count of distinct substrings for each test case.

The task is to find the minimum number of operations required to convert one string into another using delete, replace, and insert operations.

• Use dynamic programming to solve the problem efficiently.

• Create a 2D array to store the edit distances between substrings of the two input strings.

• Fill up the array based on the minimum of three possible operations: insert, delete, or replace.

• Return the value at the bottom right corner of the array as the final edit distance.

Merge overlapping intervals and return sorted list by start time.

• Sort the intervals based on start time.

• Iterate through intervals and merge overlapping ones.

• Return the merged intervals sorted by start time.

Find the length of the longest contiguous subarray that sums to zero in an array of integers.

• Iterate through the array and keep track of the running sum and its corresponding index in a hashmap.

• If the running sum is seen again, calculate the length of the subarray by subtracting the current index from the index stored in the hashmap.

• Update the maximum length of the subarray as you iterate through the array.

Examples of OOP concepts using code and principles

• Encapsulation: Using private variables and getter/setter methods

• Inheritance: Creating subclasses that inherit properties and methods from a superclass

• Polymorphism: Implementing methods with the same name but different functionality in subclasses

Protected, Private, and Public Routes manage access to web application pages based on user authentication and authorization.

• Public Routes: Accessible to everyone, no authentication required. Example: Home page, About page.

• Private Routes: Restricted to authenticated users. Example: User dashboard, Profile settings.

• Protected Routes: Similar to private routes but may allow access based on user roles or permissions. Example: Admin panel for admins only.

I have extensive knowledge in Java and SQL, focusing on database interactions and backend development.

• Proficient in JDBC for connecting Java applications to SQL databases.

• Experience in writing complex SQL queries for data retrieval and manipulation.

• Familiar with ORM frameworks like Hibernate for object-relational mapping.

• Implemented stored procedures and triggers for efficient database operations.

• Knowledge of database design principles and normalization techniques.

Middleware is software that connects different applications or services, often used for managing access control in web applications.

• Middleware acts as a bridge between the client and server, processing requests and responses.

• It can enforce role-based access control (RBAC) by checking user roles before granting access to resources.

• For example, in an Express.js application, middleware can be used to verify if a user has the 'admin' role before allowing access to admin routes.

• Mi...read more

This program covers essential Java and SQL concepts for Fullstack Engineer interviews.

• Understand Java fundamentals: classes, objects, inheritance, and polymorphism.

• Familiarize with SQL queries: SELECT, INSERT, UPDATE, DELETE.

• Practice Java collections: ArrayList, HashMap, and their use cases.

• Learn about exception handling in Java: try-catch blocks.

• Explore JDBC for database connectivity in Java applications.

API stands for Application Programming Interface. It defines the methods and data formats that applications can use to communicate with each other.

• API is a set of rules and protocols that allows different software applications to communicate with each other.

• REST API is a type of API that follows the principles of REST (Representational State Transfer) architecture.

• Cloud computing refers to the delivery of computing services over the internet, including storage, databases, net...read more

React is optimised due to virtual DOM, one-way data binding, and component-based architecture.

• Virtual DOM allows React to update only the necessary components, improving performance.

• One-way data binding ensures that data flows in a single direction, reducing the risk of bugs.

• Component-based architecture promotes reusability and modularity, making code easier to maintain.

• React's use of JSX allows developers to write HTML-like code within JavaScript, improving readability and p...read more

Async and await simplify asynchronous programming in JavaScript, making it easier to read and write code that handles promises.

• Async functions return a promise, allowing the use of await within them.

• Await pauses the execution of the async function until the promise is resolved.

• Using async/await makes code look synchronous, improving readability.

• Example: async function fetchData() { const data = await fetch(url); return data; }

• Error handling can be done using try/catch blocks ...read more

Find max continous sub array with unique elements in an array

• Use sliding window approach

• Keep track of unique elements in the window

• Update max length when a duplicate element is found

Optimizing a query involves using indexes, limiting the result set, and avoiding unnecessary joins.

• Use indexes on columns frequently used in the query's WHERE clause

• Limit the result set by using pagination or filtering criteria

• Avoid unnecessary joins by denormalizing data or using subqueries

Implementing a retry mechanism in code to handle failures and retries automatically.

• Create a function that takes a function to execute and a maximum number of retries as parameters.

• Use a loop to execute the function and catch any exceptions that occur.

• If an exception occurs, decrement the number of retries left and retry the function.

• Example: function retry(func, maxRetries) { for(let i=0; i

Dealing with ambiguous requirements and difficult challenges in a situation-based approach.

• Identifying and clarifying ambiguous requirements through effective communication

• Breaking down complex problems into smaller, manageable tasks

• Adapting to changing priorities and tight deadlines

• Collaborating with team members to brainstorm solutions

• Using critical thinking and problem-solving skills to find innovative solutions

• Managing expectations and balancing trade-offs between differe...read more