347. Top K Frequent Elements

‘’‘
347. Top K Frequent Elements
Medium

1322

87

Favorite

Share
Given a non-empty array of integers, return the k most frequent elements.

Example 1:

Input: nums = [1,1,1,2,2,3], k = 2
Output: [1,2]
Example 2:

Input: nums = [1], k = 1
Output: [1]
Note:

You may assume k is always valid, 1 ≤ k ≤ number of unique elements.
Your algorithm's time complexity must be better than O(n log n), where n is the array's size.


’‘’
class Solution:
    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
        # from collections import defaultdict
        # # counter
        # d_key_counter = defaultdict(int)
        # # key:counts
        # for n in nums:
        #     d_key_counter[n] += 1

        from collections import Counter
        d_key_counter = Counter(nums)


        frequency = [] # min heap

        for ele, count in d_key_counter.items():
            # if len(frequency) < k:
            #     heapq.heappush(frequency, (count, ele))
            # elif frequency[0][0] < count:
            #     heapq.heapreplace(frequency, (count, ele))

            heapq.heappush(frequency, (count, ele))
            if len(frequency) > k:
                heapq.heappop(frequency)

        #print(frequency)
        res = []
        for count,ele in frequency:
            res.append(ele)

        return res