leetcode/0347_top-k-frequent-elements/python3/solution.py

from collections import Counter
from heapq import heapify, heappop

class Solution:
    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
        c = Counter(nums)
        
        # Python heapq creates a min-heap but we want a max-heap built
        # against counts. Tuples are comparable in Python by default so
        # we can create a tuple of (count, element) to build the heap. To
        # mimic a max-heap, we can just negate the counts.
        heap = [(-count, val) for val, count in c.items()]
        heapify(heap)
        
        result = [None] * k
        
        for i, _ in enumerate(result):
            result[i] = heappop(heap)[1]
        
        return result