leetcode/work/Medium/Array/347.top-k-frequent-elements.js

/*
 * 347. Top K Frequent Elements
 * Difficulty: Medium
 * https://leetcode.com/problems/top-k-frequent-elements/
 *
 * ──────────────────────────────────────────────────
 *
 * 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]
 *
 * Example 3:
 *
 * Input: nums = [1,2,1,2,1,2,3,1,3,2], k = 2
 *
 * Output: [1,2]
 *
 *
 *
 * 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.
 *
 *
 *
 * Follow up: Your algorithm's time complexity must be better than O(n
 * log n), where n is the array's size.
 */

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number[]}
 */
var topKFrequent = function (nums, k) {
  const freq = {};
  for (let n of nums) freq[n] = (freq[n] || 0) + 1;

  return Object.keys(freq)
    .map(Number)
    .sort((a, b) => freq[b] - freq[a])
    .slice(0, k);
};