Top K Frequent Elements

Medium · Arrays & Hashing

Given an integer array nums and an integer k, return the k elements that occur most frequently in the array. You may return the answer in any order. It is guaranteed that among all elements there is a well-defined set of k elements with the highest frequencies, so no tie-breaking ambiguity needs to be resolved.

Examples

Input:  nums = [1,1,1,2,2,3], k = 2
Output: [1,2]
Why:    1 appears 3 times, 2 appears 2 times, 3 appears once; the two most frequent are 1 and 2.

Input:  nums = [1], k = 1
Output: [1]
Why:    The only element present is 1, so it is trivially the most frequent.

Input:  nums = [4,4,4,4,5,5,6], k = 2
Output: [4,5]
Why:    4 occurs 4 times and 5 occurs 2 times, more than 6 which occurs once.

Constraints

1 <= nums.length <= 10^5; -10^4 <= nums[i] <= 10^4; k is guaranteed to be valid (1 <= k <= number of distinct elements)

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This statement is written for CodeSpeek. The problem is part of the NeetCode 150 list; Watch NeetCode's explanation of Top K Frequent Elements. Reference solutions from the NeetCode repository (MIT) are used to verify our tests.