dataset/problem_7/buggy.py

from collections import Counter


def top_k_frequent(nums: list[int], k: int) -> list[int]:
    """Return k most frequent numbers, highest frequency first."""
    freq = Counter(nums)
    # BUG: sorts by ascending frequency instead of descending.
    ordered = sorted(freq.items(), key=lambda item: item[1])
    return [n for n, _ in ordered[:k]]