TopKElementsInList.js

// Top K Elements in List
// Given an integer array nums and an integer k, return the k most frequent elements within the array.

// The test cases are generated such that the answer is always unique.

// You may return the output in any order.

// Example 1:

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

// Output: [2,3]
// Example 2:

// Input: nums = [7,7], k = 1

// Output: [7]
// Constraints:

// 1 <= nums.length <= 10^4.
// -1000 <= nums[i] <= 1000
// 1 <= k <= number of distinct elements in nums.

class Solution {
    /**
     * @param {number[]} nums
     * @param {number} k
     * @return {number[]}
     */
    topKFrequent(nums, k) {
        const frequencyMap = new Map();

        // Count the frequency of each element
        for (let num of nums) {
            frequencyMap.set(num, (frequencyMap.get(num) || 0) + 1);
        }

        // Create an array of the elements sorted by frequency
        let frequencyMapKeys = frequencyMap.keys();
        const sortedElements = Array.from(frequencyMapKeys).sort((a, b) => frequencyMap.get(b) - frequencyMap.get(a));

        // Return the first k elements
        return sortedElements.slice(0, k);
    }
}

// class Solution {
//     /**
//      * @param {number[]} nums
//      * @param {number} k
//      * @return {number[]}
//      */
//     topKFrequent(nums, k) {
//         const count = {};
//         const freq = Array.from({ length: nums.length + 1 }, () => []);

//         for (const n of nums) {
//             count[n] = (count[n] || 0) + 1;
//         }

//         for (const n in count) {
//             let value = count[n];
//             let property = parseInt(n);
//             freq[value].push(property);
//         }

//         const res = [];
//         for (let i = freq.length - 1; i > 0; i--) {
//             for (const n of freq[i]) {
//                 res.push(n);
//                 if (res.length === k) {
//                     return res;
//                 }
//             }
//         }
//     }
// }

// Example Usage:

const solution = new Solution();

// Example 1
let nums1 = [1, 2, 2, 3, 3, 3,1,1,5,7,7,7,];
let k1 = 2;
console.log(solution.topKFrequent(nums1, k1)); // Output: [3, 2]

// Example 2
let nums2 = [7, 7];
let k2 = 1;
console.log(solution.topKFrequent(nums2, k2)); // Output: [7]