예약하고 라운드로빈 — 폭 말고 깊이를 깎기

def _fill_round_robin(shelves: list[list[str]], budget: int):
    """Spend the elastic allowance across shelves by RANK.

    Shelf-by-shelf would reproduce tail truncation one level down: the
    first shelves fully represented, the last ones absent. By rank,
    running out costs each topic a little depth instead of erasing
    whole topics -- and a missing subject damages a survey far more
    than thinner coverage of every subject.
    """
    lines, spent, dropped = [], 0, 0
    deepest = max((len(s) for s in shelves), default=0)
    for rank in range(deepest):
        for shelf in shelves:
            if rank >= len(shelf):
                continue
            cost = len(shelf[rank]) + 1
            if spent + cost > budget:
                dropped += 1
                continue          # keep going: a later shelf may fit
            lines.append(shelf[rank])
            spent += cost
    return lines, dropped


# The test that makes the reservation real. It does NOT test a normal
# day -- a normal day fits, and passes either way. It floods.
def test_a_wide_day_cannot_evict_the_reserved_sections(con):
    seed_shelves(con, count=40, headlines_each=200)   # far over budget
    corpus, stats = build_corpus(con)

    assert "X temperature" in corpus, "reserved section was evicted"
    assert "Yesterday's brief" in corpus
    assert stats["samples"] > 0
    assert stats["headlines_dropped"] > 0     # the elastic part absorbed it
    assert len(corpus) <= CORPUS_MAX_CHARS