Meta Frontend Engineer Interview Questions

In a social media platform, suggesting friends from mutual connections increases user engagement. This problem mimics exploring connections in a graph representation of users.
Problem statement: Given a list of user connections represented as edges, determine the number of mutual friends between two given users using Depth First Search (DFS).
- Method Signature: mutualFriends(connections: [number[], number[]], userA: number, userB: number): numberExample 1:
Input: connections = [[1, 2], [2, 3], [3, 4], [1, 4], [2, 4]], userA = 1, userB = 2
Output: 2
Explanation: Mutual friends for users 1 and 2 are [4].Example 2:
Input: connections = [[1, 2], [2, 3], [3, 1]], userA = 1, userB = 3
Output: 1
Explanation: The mutual friend is 2.Constraints:
- 1 <= connections.length <= 10^4
- 1 <= userA, userB <= 10^5

As users scroll through their news feeds, loading efficiency is crucial to enhance user experience. This problem simulates a situation in which you need to efficiently fetch a subset of posts based on the number of visible posts and the current scroll position.
Problem statement: Given an array of integers representing the post IDs and a k representing the number of posts to load, return an array containing the k most recent post IDs starting from the specified index.
- Method Signature: getRecentPosts(posts: number[], startIndex: number, k: number): number[]Example 1:
Input: posts = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], startIndex = 2, k = 4
Output: [3, 4, 5, 6]
Explanation: Starting from index 2, the next 4 posts are from IDs 3 to 6.Example 2:
Input: posts = [1, 2, 3, 4, 5], startIndex = 3, k = 2
Output: [4, 5]
Explanation: Starting from index 3, the next 2 posts are 4 and 5.Constraints:
- 1 <= posts.length <= 10^5
- 0 <= startIndex < posts.length
- 1 <= k <= 10

Managing notifications across different platforms and ensuring a user-friendly interface is paramount for keeping users engaged. This design focuses on a central notification management system.
Problem statement: Implement a class NotificationSystem that supports sending notifications and retrieving them by user.
- Method Signatures:
- constructor() — initializes the notification system.
- sendNotification(userId: string, message: string): void — sends a notification to the specified user.
- getNotifications(userId: string): string[] — retrieves notifications for the specified user.Example 1:
Input: system = new NotificationSystem(); system.sendNotification('user1', 'Welcome!');
Output: system.getNotifications('user1') => ['Welcome!']Constraints:
- 1 <= userId.length <= 10^5
- 1 <= message.length <= 500

Displaying images efficiently in a carousel format is essential for user engagement in photo-sharing apps. This design focuses on class structure that manages the image data, current state, and transition logic for the carousel.
Problem statement: Create a class ImageCarousel that manages images and transitions between them.
- Method Signatures:
- constructor(images: string[]) — initializes the carousel with the provided image URLs.
- next(): string — moves to the next image and returns the URL.
- prev(): string — moves to the previous image and returns the URL.
- getCurrentImage(): string — returns the URL of the current image.Example 1:
Input: carousel = new ImageCarousel(['img1.jpg', 'img2.jpg', 'img3.jpg'])
Output: carousel.getCurrentImage() => 'img1.jpg'
Output: carousel.next() => 'img2.jpg'Constraints:
- 1 <= images.length <= 100
- All strings in images are valid URLs.