Top K Frequent Elements in Integer Array Efficiently

snapchat Given a non-empty array of integers, return the k most frequent elements. Input: An integer array containing n numbers and an integer k, indicating to return the top k frequent elements. Output: An array containing the k most frequent integers. Note: You may assume k is always valid, 1 ≤ k ≤ the number of unique elements. Your algorithm's time complexity must be better than O(n log n), where n is the array's size. How to optimize if k is very large, e.g., close to n? Example: Input: nums = [1,1,1,2,2,3], k = 2 Output: [1, 2] Input: nums = [1], k = 1 Output: [1] The solution should consider the case when dealing with extremely large data files. Example Input [1,1,1,2,2,3] 2