leetcode/docs/array/347.mdx

---
title: LC-347
description: Top K Frequent Elements
---

## Examples

| Input                              | Output   |
| ---------------------------------- | -------- |
| `nums = [1,1,1,2,2,3], k = 2`      | `[1,2]`  |
| `nums = [1], k = 1`                | `[1]`    |
| `nums = [1,2,1,2,1,2,3,1,3,2], k = 2` | `[1,2]` |

## Hints

<Accordions type="single">
  <Accordion title="Constraints">
    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.
  </Accordion>
  <Accordion title="Problem Statement">
    Given an integer array nums and an integer `k`, return the `k` most frequent elements.
    You may return the answer in any order.

    Follow up: Your algorithm's time complexity must be better than `O(n log n)`, where n is the array's size.
  </Accordion>
</Accordions>

## Solution

```js
/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number[]}
 */

var topKFrequent = function (nums, k) {
  // Default for Hammer
  const freq = {};
  for (let n of nums) freq[n] = (freq[n] || 0) + 1;

  // Problem Specific
  // Sort unique values by descending frequency, take the first k
  return Object.keys(freq)
    .map(Number)
    .sort((a, b) => freq[b] - freq[a])
    .slice(0, k);
};
```