Top K Frequent

Python data engineering interview problem. Difficulty: advanced. Pattern: Heaps. About 18 minutes. Part of the Pro drill bank.

Return the k most frequent numbers, sorted for stability. Treat this as a production helper: match the contracted return shape, including empty and duplicate inputs.

A report needs the most common ids, but its output must be stable so 2 runs can be compared. Return the k most frequent values, then sort those selected values in ascending order. Frequency chooses the group; numeric order controls the final display. Write top_k_frequent(nums: list, k: int) -> list. In [1, 1, 1, 2, 2, 3], the two most frequent values are 1 and 2, so the stable result is [1, 2]. The starter file already contains the function name, harness and print lines. Keep them and fill only the function body.

Requirements

• Count every value.
• Select exactly k values unless fewer unique values are available.
• Sort the selected values ascending.

Constraints

• Duplicates count toward frequency and k is positive.
• Return a list of values, not (value, count) pairs.

Examples

Input: top_k_frequent([1, 1, 1, 2, 2, 3], 2) Output: [1, 2] 1 and 2 are most frequent; sorted.

Topics: lakebench, python, frequency, heap.

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