Implement image carousel with comments and upvotes

Q: Implement image carousel with comments and upvotes

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Question

Implement an image carousel that supports:

cycling forward/backward and autoplay with a configurable interval;
a per-image comment thread with create/read/edit/delete;
upvoting/downvoting comments and returning the top-k comments per image ordered by score, breaking ties by recency. Design the data structures to support add/delete comment, update vote, and query top-k efficiently at scale (up to 10^5 images and 10^6 comments across images). Specify the time/space complexities, the APIs you would expose (including pagination of comments), and how you would prevent double-counting when a user rapidly toggles votes.

Implement image carousel with comments and upvotes

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