frequencySort.js

/**
Given an array of integers nums, sort the array in increasing order based on the frequency of the values. If multiple values have the same frequency, sort them in decreasing order.

Return the sorted array.

Example 1:
Input: nums = [1,1,2,2,2,3]
Output: [3,1,1,2,2,2]
Explanation: '3' has a frequency of 1, '1' has a frequency of 2, and '2' has a frequency of 3.

Example 2:
Input: nums = [2,3,1,3,2]
Output: [1,3,3,2,2]
Explanation: '2' and '3' both have a frequency of 2, so they are sorted in decreasing order.

Example 3:
Input: nums = [-1,1,-6,4,5,-6,1,4,1]
Output: [5,-1,4,4,-6,-6,1,1,1]
 
Constraints:
1 <= nums.length <= 100
-100 <= nums[i] <= 100

* @param {number[]} nums
* @return {number[]}
*/
var frequencySort = function(nums) {
    const freqMap = new Map();
    
    for (const num of nums) {
        freqMap.set(num, (freqMap.get(num) || 0) + 1);
    }
    
    return nums.sort((a, b) => {
        const freqA = freqMap.get(a);
        const freqB = freqMap.get(b);
    
        if (freqA === freqB) {
        return b - a; // Sort in decreasing order if frequencies are the same
        }
        return freqA - freqB; // Sort by frequency in increasing order
    });   
};