Staff Software Engineer, Backend, ML

Uber

Let's dive into recursion. 1. Explain the concept of recursion. What are the base case and recursive step, and why are they essential? 2. Write a recursive function in your language of choice to calculate the factorial of a non-negative integer. For example, factorial(5) should return 120 (5 * 4 * 3 * 2 * 1). 3. Explain how recursion works under the hood using the call stack. Illustrate with the factorial example how function calls are added and removed from the stack. 4. Discuss the advantages and disadvantages of using recursion compared to iteration. When might recursion be a better choice, and when should it be avoided? 5. What is tail recursion, and why is it important? Explain how tail call optimization can improve performance in some languages. 6. Write a recursive function to solve the Tower of Hanoi puzzle. This classic problem involves moving disks from one peg to another with specific constraints. 7. How does memoization improve the performance of recursive functions? Give an example of a problem where memoization can significantly reduce computation time (e.g., Fibonacci sequence). 8. Describe a scenario where recursion might lead to a stack overflow error. How can you prevent or mitigate this issue? 9. Implement a recursive function to perform a depth-first search (DFS) on a binary tree. Show how to traverse the tree and print the values of the nodes. 10. Explain the concept of mutual recursion and provide an example. Mutual recursion is when two functions call each other.

Uber

System Design: Google Calendar Let's design a system similar to Google Calendar. Consider the following requirements: Functionality: Users should be able to create, read, update, and delete (CRUD) events. Events should have a title, description, start time, end time, location, and attendees. Recurring Events: Support recurring events (e.g., daily, weekly, monthly) with options for specifying exceptions (e.g., skip a specific instance). Invitations and Notifications: Users should be able to invite other users to events. Invited users should receive notifications about new events, updates, and cancellations. Implement a notification system, detailing frequency and method (e.g., email, push notification). Reminders: Users should be able to set reminders for events (e.g., 10 minutes before, 1 hour before). Time Zones: The system must correctly handle events across different time zones. Availability: Users should be able to view the availability of other users when scheduling events (free/busy). Scalability: The system should be able to handle a large number of users and events, ensuring responsiveness and reliability. How would you scale the system to accommodate millions of users and concurrent events? Consistency: Ensure data consistency across different users' views of the same event. Conflict Resolution: Address how to handle conflicting events and notify users accordingly. Specifically address these points in your design: Data model: How would you represent events, users, and their relationships in a database? API design: What API endpoints would you provide for creating, reading, updating, and deleting events? Concurrency and locking: How would you handle concurrent access to events to prevent data corruption? Notification system: How would you implement the notification system for event invitations, updates, and reminders? Scalability strategies: What strategies would you use to scale the system to handle a large number of users and events? Conflict Detection: How will the system determine event conflicts, and what notification mechanisms will be in place?

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Describe a time you disagreed with your team members.