刷题记录：347. 前 K 个高频元素

347. 前 K 个高频元素

1 暴力计数+排序 O(nlogn)

class Solution:
    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
        count = collections.defaultdict(int)
        
        for val in nums:
            count[val] += 1

        return sorted(count.keys(), key = lambda x : count[x], reverse = True)[:k]

2 堆 O(nlogk)

class Solution:
    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
        heap = []
        count = collections.defaultdict(int)

        for num in nums:
            count[num] += 1

        for key, val in count.items():
            if len(heap) < k:
             	# remember to change the order
                heappush(heap, (val, key))
            elif val > heap[0][0]:
                heapreplace(heap, (val, key))

        return [_[1] for _ in heap]