Dedupe titles in per-shelf viewport

You are rendering a streaming app home page.

• The home page consists of shelves displayed from top to bottom.
• Each shelf contains a list of titleId values (integers).
• Each shelf’s horizontal viewport can show at most X titles.
• Assume the vertical viewport is unlimited (i.e., you process shelves in order, top to bottom).

Implement a function that filters titles while preserving order under the following deduplication rules:

1. Global dedupe within the visible region:
   • While building the first X output titles for a shelf, you must skip any titleId that has already appeared in the visible region (first X output titles) of any earlier shelf.
2. Local dedupe after the visible region:
   • After a shelf has already produced X output titles, continue outputting additional titles from that shelf, but now only dedupe within the same shelf (i.e., skip repeats that have already been output in this shelf).
   • Global deduplication no longer applies past position X within a shelf.

Function signature

• Input: shelves: List[List[int]] , X: int
• Output: List[List[int]] (the filtered shelves)

Notes

• Preserve the original relative order of titles within each shelf.
• If a shelf has fewer than X eligible titles (after global dedupe), it may output fewer than X titles.

Example

If X = 2 and shelves are:

• Shelf 1: [1, 2, 1, 3]
• Shelf 2: [2, 4, 2, 5]

Then:

• Shelf 1 visible region (first 2 outputs) becomes [1, 2] (global seen = {1,2} ), then locally can output 3 (skipping the repeated 1 ).
• Shelf 2 visible region cannot use 2 (already globally visible), so it outputs [4, 2] as its first 2 outputs (4 is new globally visible; once the shelf has hit X outputs, 2 is allowed even though it was globally visible). After that it can output 5 .

So the output is [[1, 2, 3], [4, 2, 5]].

Specify and implement the algorithm.