347_前_K_个高频元素

类型：堆

• 347. 前 K 个高频元素 💛

  https://leetcode-cn.com/problems/top-k-frequent-elements/

  ❓ 返回数组中出现频率前 k 高的元素。

  💡 哈希 + 堆

  先用哈希记录每个元素的出现次数。再以出现次数为比较键构建堆。

  class Solution:
      def topKFrequent(self, nums: List[int], k: int) -> List[int]:
          if not nums:
              return []
          counts = {}
          for num in nums:
              if num in counts:
                  counts[num] += 1
              else:
                  counts[num] = 1
  
          heap = []
          for num in counts:
              count = counts[num]
              if len(heap) < k or count > heap[0][0]:
                  heapq.heappush(heap, (counts[num], num))
              if len(heap) > k:
                  heapq.heappop(heap)
          ans = []
          for (_, num) in heap:
              ans.append(num)
          return ans