Sr. Software Engineer, Web Platform

Uber

Given a boolean matrix, find the number of islands. An island is a group of connected 1s or a standalone 1. A cell can be connected to 8 neighbors (2 vertical, 2 horizontal, and 4 diagonal). For example, consider the following boolean matrix: [[1, 1, 0, 0, 0], [1, 1, 0, 0, 0], [0, 0, 1, 0, 0], [0, 0, 0, 1, 1]] In this matrix, there are three islands. The first island consists of the 1s in the top-left corner. The second island is the single 1 in the middle of the matrix. The third island is formed by the two 1s in the bottom-right corner. As another example: [[1, 0, 1, 0], [0, 1, 0, 1], [1, 0, 1, 0], [0, 1, 0, 1]] This matrix contains eight islands. Your task is to implement a function that takes a two-dimensional boolean matrix as input and returns the number of islands present in the matrix. The function should handle cases where the matrix is empty or contains no islands (all 0s). Consider edge cases where an island touches the boundary of the matrix. Can you provide an efficient algorithm to solve this problem, taking into account the 8-directional connectivity?

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?

Uber

Describe a time you disagreed with your team members.