40+ SDE Intern Interview Questions and Answers

Count the occurrences of each character in a given string including special characters.

• Create test cases for empty string

• Test for string with only one character

• Test for string with all characters being the same

• Test for string with all characters being different

• Test for string with special characters

Find square root of a number using basic arithmetic operations without power operator and inbuilt libraries.

• Use binary search to find the integer part of the square root

• Use long division method to find the decimal part of the square root

• Repeat the above steps until desired accuracy is achieved

• Handle edge cases like negative numbers and numbers less than 1

Remove duplicate characters from a string while preserving order.

• Create an empty string to hold the result.

• Iterate through each character in the input string.

• If the character is not already in the result string, add it.

• Return the result string.

Caching is the process of storing frequently accessed data in a temporary storage to improve performance.

• Caching reduces the need to fetch data from the original source, improving response time.

• It helps in reducing network traffic and server load.

• Caching can be done at various levels like browser caching, CDN caching, and server-side caching.

• Examples of caching include browser caching of website assets, CDN caching of static content, and database query result caching.

To change permissions for a file, you can use the chmod command in the terminal.

• Use the chmod command followed by the permission code and the file name

• Permission codes include 'u' for user, 'g' for group, and 'o' for others, along with 'r' for read, 'w' for write, and 'x' for execute

• For example, to give read and write permissions to the user for a file named 'example.txt', you can use 'chmod u+rw example.txt'

Addition of two linked lists and return the result as a linked list.

• Traverse both linked lists simultaneously

• Add corresponding nodes and carry over the sum

• Create a new linked list with the sum

I have worked on various projects using different tech stacks including Java, Python, and JavaScript.

• Developed a web application using Java Spring Boot framework

• Created a data analysis tool using Python libraries such as Pandas and NumPy

• Built a real-time chat application using JavaScript and Node.js

• Implemented machine learning algorithms using Python's scikit-learn library

• Worked on a mobile application using React Native framework

SQL query to manage pick and drop of passengers in a transport system

• Create a table for passengers with columns like passenger_id, name, pick_up_location, drop_off_location, etc.

• Create a table for transport vehicles with columns like vehicle_id, driver_name, capacity, etc.

• Use JOIN to link the two tables based on pick_up_location and drop_off_location.

• Consider adding a table for routes and scheduling for better organization.

• Example: SELECT * FROM passengers p JOIN vehicles v O...read more

Multithreading is not natively supported in JavaScript, but can be achieved through Web Workers.

• JavaScript is a single-threaded language, meaning it can only execute one task at a time.

• Web Workers allow for multithreading in JavaScript by running scripts in the background.

• Web Workers can communicate with the main thread using message passing.

• Examples of tasks that can benefit from multithreading include heavy computations and long-running processes.

Meta is a leading company in AI space with a focus on developing innovative technologies and solutions.

• Meta (formerly Facebook) is known for its advanced AI research and development.

• Meta uses AI for various applications such as content moderation, personalized recommendations, and virtual assistants.

• Meta's AI technologies power products like facial recognition, language translation, and image recognition.

Find leaf nodes in a binary tree and print path to each leaf node.

• Traverse the binary tree using depth-first search (DFS)

• When reaching a leaf node, store the path from root to that leaf node

• Repeat the process for all leaf nodes in the tree

Function to insert, delete, and print a linked list

• Create a Node class with data and next pointer

• Implement insert function to add a new node at the end of the linked list

• Implement delete function to remove a node by value

• Implement print function to display all elements in the linked list

Find the deepest left node in a binary tree.

• Traverse the tree recursively and keep track of the depth and whether the current node is a left node.

• If the current node is a leaf node and its depth is greater than the deepest left node found so far, update the deepest left node.

• Return the deepest left node found.

• Example: For the binary tree with root node 1, left child 2, and left child of 2 being 4, the deepest left node is 4.

• Example: For the binary tree with root node 1, left ...read more

Optimizing code and estimating time complexity

• Identify bottlenecks in the code and optimize them

• Use efficient data structures and algorithms

• Analyze the code to determine its time complexity

• Consider worst-case, best-case, and average-case scenarios

• Use Big O notation to express the time complexity

Use binary search to efficiently search for an element in a sorted matrix.

• Start from the top right corner of the matrix

• If the target is greater than the current element, move down

• If the target is less than the current element, move left

• Repeat until the target is found or all elements are checked

Virtual DOM is a lightweight copy of the actual DOM used for efficient updates.

• Virtual DOM is a concept used in modern web development frameworks like React.

• It is a lightweight copy of the actual DOM that is used to track changes and update the actual DOM efficiently.

• When a change is made to the virtual DOM, it is compared with the previous version to identify the minimum number of changes required to update the actual DOM.

• This approach reduces the number of updates required ...read more

Rotate matrix elements with k positions left

• Create a temporary array to store the first k elements of each row

• Shift the remaining elements in each row to the left by k positions

• Replace the last k elements in each row with the elements from the temporary array

Single way binding updates the view when the model changes, while two way binding updates both the view and the model.

• Single way binding updates the view when the model changes, but not vice versa.

• Two way binding updates both the view and the model when either changes.

• Single way binding is commonly used in frameworks like AngularJS, while two way binding is used in frameworks like Vue.js.

Java Hibernate is an ORM (Object-Relational Mapping) framework that simplifies database operations in Java applications.

• Hibernate maps Java classes to database tables and vice versa

• It provides automatic generation of SQL queries based on Java objects

• Hibernate handles the mapping of Java data types to SQL data types

• It supports caching mechanisms to improve performance

• Hibernate simplifies complex database operations like transactions and queries

Lazy loading in React is a technique used to improve performance by loading components only when they are needed.

• Lazy loading helps reduce the initial load time of a web application by splitting the code into separate bundles.

• It allows components to be loaded asynchronously, improving the overall user experience.

• Lazy loading is commonly used for optimizing the loading of images, videos, or heavy components in React applications.

Count occurrences of a given element in a sorted array.

• Use binary search to find the first and last occurrence of the element.

• Subtract the indices to get the count.

• Handle edge cases like element not present in the array.

Make In India initiative aims to boost manufacturing sector, create jobs, and attract foreign investment.

• Promotes domestic manufacturing and reduces dependency on imports

• Encourages foreign companies to set up manufacturing units in India

• Generates employment opportunities for the local population

• Boosts economic growth and contributes to GDP

• Enhances skill development and technology transfer

• Examples: Apple manufacturing iPhones in India, Samsung setting up production units

Use Floyd's Tortoise and Hare algorithm to detect a loop in a linked list.

• Initialize two pointers, slow and fast, at the head of the linked list.

• Move slow pointer by one step and fast pointer by two steps.

• If they meet at any point, there is a loop in the linked list.

Prop drilling is the process of passing data through multiple layers of components in a React application.

• Prop drilling involves passing props from a parent component to multiple levels of nested child components.

• It can lead to code that is harder to maintain and understand, as props need to be passed through intermediary components that do not actually use the data.

• One way to avoid prop drilling is by using context or Redux to manage state and make it accessible to any compo...read more

A program for stack operations

• Create a stack using an array or linked list

• Implement push() and pop() functions

• Check for stack overflow and underflow

• Implement peek() function to view top element

• Example: stack.push(5), stack.pop(), stack.peek()

Min-stack is implemented using O(N) space by keeping track of minimum value at each element.

• Use two stacks - one to store the actual elements and another to store the minimum value at each step.

• When pushing an element, check if it is smaller than the current minimum and update the minimum stack accordingly.

• When popping an element, also pop from the minimum stack if the popped element is the current minimum.

WhatsApp is a messaging app that allows users to send text messages, voice messages, images, and videos.

• End-to-end encryption for secure communication

• Message delivery status indicators

• Group chat functionality

• Media sharing capabilities

• Online/offline status indicators

Array is a fixed-size data structure while ArrayList is a dynamic-size data structure in Java.

• Array is a static data structure with a fixed size, while ArrayList is a dynamic data structure that can grow or shrink in size.

• Arrays can hold primitive data types and objects, while ArrayList can only hold objects.

• Arrays use square brackets [] for declaration, while ArrayList is a class in Java's collection framework.

• Arrays are faster than ArrayList for accessing elements, but Arra...read more

The right view of a binary tree shows the nodes that are visible when viewing the tree from the right side.

• The right view of a binary tree can be obtained by performing a level order traversal and keeping track of the rightmost node at each level.

• Nodes that are visible from the right side are the ones that are the rightmost at their respective levels.

• For example, in the binary tree: 1 / \ 2 3 / \ / \ 4 5 6 7 the right view would be [1, 3, 7].

Event Loop is a mechanism that allows JavaScript to perform non-blocking operations by handling asynchronous tasks.

• Event Loop is a part of JavaScript runtime that continuously checks the call stack and the callback queue.

• It processes tasks in the callback queue only when the call stack is empty.

• Event Loop helps in handling asynchronous operations like setTimeout, AJAX requests, and event listeners.

Node.js is a runtime environment that allows you to run JavaScript code outside of a web browser.

• Node.js is built on Chrome's V8 JavaScript engine.

• It uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.

• Node.js is commonly used for building server-side applications and APIs.

• It has a large ecosystem of open-source libraries available through npm (Node Package Manager).

Implement a stack that supports push, pop, top, and retrieving the minimum element in constant time.

• Use two stacks - one to store the actual elements and another to store the minimum values.

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

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

• Top operation can be implemented by returning the top element of the main stack.

• GetMin op...read more

Left view of a binary tree is the set of nodes visible when the tree is viewed from the left side.

• Traverse the tree level by level from left to right

• At each level, add the first node encountered to the result array

• Continue this process until all levels are traversed

Sliding Window Problem involves finding a subarray of fixed size k with the maximum sum.

• Use a sliding window approach to iterate through the array and keep track of the sum of elements within the window.

• Slide the window by removing the first element and adding the next element in each iteration.

• Keep track of the maximum sum found so far and update it if a new maximum is found.

Create a linked list

• Define a Node class with data and next pointer

• Create a LinkedList class with methods like insert, delete, search

• Initialize head pointer to null and update it as nodes are added

Rod cutting problem involves finding the optimal way to cut a rod into pieces to maximize profit.

• Identify the lengths at which the rod can be cut.

• Calculate the maximum profit that can be obtained by cutting the rod at different lengths.

• Use dynamic programming to solve the problem efficiently.

• Example: Given a rod of length 8 and prices for different lengths as [1, 5, 8, 9, 10, 17, 17, 20], the maximum profit is 22 by cutting the rod into pieces of length 2 and 6.

Reverse a linked list by changing the direction of pointers

• Start with three pointers: prev, current, next

• Iterate through the list, updating pointers to reverse the direction

• Update the head of the list to be the last node

Dutch National Algorithm is a sorting algorithm that partitions an array into three sections based on a pivot element.

• Choose a pivot element

• Partition the array into three sections: elements less than the pivot, elements equal to the pivot, and elements greater than the pivot

• Recursively apply the algorithm to the subarrays

Reverse the array of strings

• Create a new array and iterate through the original array in reverse order, adding each element to the new array

• Alternatively, you can use the reverse() method on the array itself

Projects are tasks or assignments undertaken to achieve specific goals within a set timeframe.

• Projects involve planning, execution, and monitoring of tasks to achieve a desired outcome.

• They typically have defined objectives, timelines, and resources allocated.

• Examples include developing a mobile app, implementing a new software system, or conducting a research study.

Kadane's Algorithm is used to find the maximum subarray sum in an array of integers.

• Iterate through the array and keep track of the maximum sum ending at each index.

• If the current element is greater than the sum ending at the previous index, start a new subarray.

• Return the maximum sum found.

• Example: For array [-2, 1, -3, 4, -1, 2, 1, -5, 4], the maximum subarray sum is 6 (from index 3 to 6).