Top K Frequent Elements

Description

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

Example 1:

Input: nums = [1,1,1,2,2,3], k = 2
Output: [1,2]

Example 2:

Input: nums = [1], k = 1
Output: [1]

Constraints:

1 <= nums.length <= 10⁵
k is in the range [1, the number of unique elements in the array].
It is guaranteed that the answer is unique.

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

Solution(javascript)

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number[]}
 */
var topKFrequent = function(nums, k) {
    let frequency = {};
    for (let i = 0; i < nums.length; i++) {
        if (frequency[nums[i]]) {
            frequency[nums[i]] += 1
        } else {
            frequency[nums[i]] = 1
        }
    }
    
    let sorted = Object.entries(frequency).sort((a,b)=> b[1] - a[1]) 
    let res = []
    for (let i = 0; i < k; i++) {
        res.push(sorted[i][0])
    }

    return res
};