20+ Shree Laljee Prashikshan Kendra Interview Questions and Answers

An unique id for a massive parallel system can be generated using a combination of timestamp, machine id and a random number.

• Use a timestamp to ensure uniqueness

• Include a machine id to avoid collisions in a distributed system

• Add a random number to further increase uniqueness

• Consider using a UUID (Universally Unique Identifier) for simplicity

• Ensure the id generation algorithm is thread-safe

Instagram uses a notification system to alert users when they are tagged and displays reels on the profile page based on user preferences and algorithms.

• Instagram uses a push notification system to alert users when they are tagged in a post or story.

• Reels are displayed on the profile page based on user engagement, preferences, and algorithms.

• The Explore page also suggests reels to users based on their interests and interactions on the platform.

OLA application uses GPS to track cabs on map and assign them to customers based on location and availability.

• OLA application uses GPS technology to track the location of cabs in real-time.

• Customers input their location and destination in the app to request a cab.

• The app matches the customer with the nearest available cab and assigns it to them.

• Customers can track the cab's movement on the map in real-time as it approaches their location.

Implement a linked list with methods to find the second largest and second smallest elements.

• Create a linked list class with methods to insert elements, find second largest, and find second smallest.

• Traverse the linked list to find the largest and smallest elements, then find the second largest and second smallest.

• Handle edge cases such as empty list or lists with less than 2 elements.

• Consider using a priority queue to efficiently find the second largest and second smallest e...read more

You can invoke a method using a constructor by creating an instance of the class and calling the method, or by using a variable that holds a reference to the method.

• Invoke method using constructor: ClassName obj = new ClassName(); obj.methodName();

• Invoke method using variable: ClassName obj = new ClassName(); Runnable r = obj::methodName; r.run();

Fragments can communicate among themselves using interfaces, shared view models, and activity callbacks.

• Use interfaces to define communication contract between fragments

• Implement the interface in the hosting activity and pass it to the fragments

• Use shared view models to share data between fragments

• Use activity callbacks like onActivityResult() to communicate between fragments

Design HLD and LLD of Zomato

• High-Level Design (HLD) should include the overall architecture of the system, including components and their interactions

• Low-Level Design (LLD) should include detailed design of each component, including data structures, algorithms, and interfaces

• HLD should consider scalability, availability, and fault tolerance

• LLD should consider performance, security, and maintainability

• Example components of Zomato system: user interface, search engine, recommen...read more

Designing Uber apps for both riders and drivers

• For the rider app, focus on ease of use and quick booking process

• For the driver app, focus on real-time updates and navigation

• Both apps should have a rating system and payment integration

• Implement features like surge pricing, ride history, and in-app messaging

Find the character with the highest frequency in a given string.

• Iterate through the string and count the frequency of each character using a hashmap.

• Track the character with the highest frequency as you iterate.

• Return the character with the highest frequency at the end.

Callback method in Java allows passing a function as an argument to another function. Alternatives include using interfaces, lambda expressions, and method references.

• Callback method allows passing a function as an argument to another function

• Alternatives include using interfaces, lambda expressions, and method references

• Example: Using Runnable interface in Java to pass a function as a callback

System design specific to domain

• Understand the domain and its requirements

• Identify the key components and their interactions

• Choose appropriate technologies and architecture

• Consider scalability and maintainability

Zomato is a food delivery and restaurant discovery platform that connects users with local restaurants.

• Zomato uses a microservices architecture to handle its various functionalities.

• The system is designed to handle a large number of concurrent users and requests.

• Zomato uses a combination of relational and NoSQL databases to store data.

• The platform uses machine learning algorithms to provide personalized recommendations to users.

• Zomato also integrates with various third-party ...read more

A parking lot system that manages parking spots and vehicles.

• Create a class for parking lot with attributes like total number of spots, available spots, etc.

• Create a class for vehicle with attributes like license plate number, type, etc.

• Implement methods for parking a vehicle, removing a vehicle, and checking availability of spots.

• Use data structures like arrays and maps to store and retrieve information.

• Consider implementing a payment system for parking fees.

High level system design involves creating an abstract representation of a system's architecture.

• Identify the system's components and their interactions

• Define the system's boundaries and interfaces

• Consider scalability, reliability, and maintainability

• Use diagrams and models to communicate the design

Find and print the longest common subsequence in an array of strings

• Use dynamic programming to find the longest common subsequence

• Iterate through the array of strings to find common characters

• Print the longest common subsequence found

Search for a number in a consecutive array of strings

• Iterate through the array and convert each string to a number

• Check if the numbers are consecutive by comparing with the next number

• Return the number if found, otherwise return a message indicating not found

Detect if there is a loop in a graph.

• Use Depth First Search (DFS) to traverse the graph.

• If a node is visited twice during DFS, then there is a loop.

• Maintain a visited set to keep track of visited nodes.

• If a node is already in the visited set, then there is a loop.

Implementing LRU Cache without using LinkedHashMap

• Use a doubly linked list to maintain the order of keys based on their recent usage

• Use a hashmap to store key-value pairs for quick access

• When a new key is accessed, move it to the front of the linked list and update the hashmap accordingly

• When the cache is full, remove the least recently used key from the end of the linked list and hashmap

Solid design principles are fundamental guidelines for designing software that is maintainable, scalable, and efficient.

• Follow the SOLID principles (Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion)

• Use design patterns like Factory, Singleton, Observer, etc. to solve common design problems

• Keep code modular, reusable, and easy to understand

• Separate concerns and avoid tight coupling between components

Hashmap is not thread-safe, while ConcurrentHashMap is thread-safe and allows for concurrent access.

• Hashmap is not thread-safe and can lead to race conditions in a multi-threaded environment.

• ConcurrentHashMap is thread-safe and allows for concurrent access by multiple threads without the need for external synchronization.

• ConcurrentHashMap achieves thread-safety by dividing the map into segments, each of which can be locked independently.

• ConcurrentHashMap is preferred for mult...read more

Working code with edge cases is code that has been tested with extreme inputs to ensure it functions correctly.

• Edge cases are inputs that are unlikely to occur but can cause unexpected behavior if not handled properly.

• Examples of edge cases include empty inputs, null values, and inputs at the limits of the data type's range.

• Working code with edge cases should be thoroughly tested to ensure it functions correctly in all scenarios.

GCD is a low-level API for managing concurrent operations, while Operation Queue is a higher-level API built on top of GCD.

• GCD is a C-based API for managing queues of tasks, while Operation Queue is an Objective-C class that provides a more object-oriented way to manage tasks.

• GCD is more low-level and requires manual management of queues and tasks, while Operation Queue handles many of these details for you.

• Operation Queue allows you to easily cancel, suspend, and resume oper...read more

Implementing infinite scroll for a web application

• Use a front-end framework like React or Angular to handle the scrolling functionality

• Fetch additional data from the server as the user scrolls down the page

• Update the UI with the new data without reloading the entire page