python 前 k 个高频元素

可以使用 Counter 对列表中的元素进行统计，然后使用堆排序找出前 k 个高频元素。

具体实现如下：

from collections import Counter
import heapq

def top_k_frequent(nums, k):
    counter = Counter(nums)
    heap = []
    for num, freq in counter.items():
        if len(heap) < k:
            heapq.heappush(heap, (freq, num))
        else:
            if freq > heap[0][0]:
                heapq.heappop(heap)
                heapq.heappush(heap, (freq, num))
    res = []
    while heap:
        res.insert(0, heapq.heappop(heap)[1])
    return res

示例：

>>> nums = [1, 1, 1, 2, 2, 3]
>>> top_k_frequent(nums, 2)
[1, 2]