Top K Frequent Elements

Subsets

Kth Largest Element in an Array

Return the k values that occur most often in an integer array.

Given integer array `nums` and integer `k`, return the k most frequent elements from highest to lowest frequency. The answer is guaranteed unique.

## Example
```
Input: {"nums":[1,1,1,2,2,3],"k":2}
Output: [1,2]
```

**Constraints**
- 1 <= nums.length <= 100000
- 1 <= k <= the number of distinct values
- The answer is unique.

**Follow-up**
Can you beat O(n log n) with frequency buckets?

- Identify the required output and the state that changes.
- Use the examples to rule out tempting but incorrect interpretations.

Understand the Goal

- This problem is best exposed by Bucket values by frequency and scan buckets from high to low.
- Maintain only the state needed for the next operation.

Choose the Core Pattern

- Process each state once when possible.
- Record state before scheduling dependent work to avoid duplicates.

Build the Algorithm

- Verify the smallest input, impossible cases, and repeated values where allowed.
- Keep output ordering deterministic.