0347-Top-K-Frequent-Elements.py

'''
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]:
        count = {}
        for num in nums:
            count[num] = count.get(num, 0) + 1
        return heapq.nlargest(k, count.keys(), key = count.get)