Top K Frequent Elements

Medium~25 min

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

It is guaranteed that the answer is unique.

Examples

Example 1
Input: nums = [1,1,1,2,2,3], k = 2
Output: [1, 2]
Explanation: 1 appears 3 times and 2 appears 2 times. These are the 2 most frequent elements.
Example 2
Input: nums = [1], k = 1
Output: [1]
Explanation: Only one element, so it is the most frequent.
Example 3
Input: nums = [4,4,4,1,1,2,2,2,3], k = 2
Output: [4, 2]
Explanation: 4 appears 3 times and 2 appears 3 times (tied). Both are top-2 most frequent.

Constraints

  • 1 <= nums.length <= 10^5
  • -10^4 <= nums[i] <= 10^4
  • k is in the range [1, the number of unique elements in the array]
  • It is guaranteed that the answer is unique.
  • Expected time complexity: O(n)
Code
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Output

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