---
title: '1636. Sort Array by Increasing Frequency'
description: 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
sidebar:
  label: 'Sort Array by Increasing Frequency'
  badge: 'Easy'
---

<Badge variant="accent">Array</Badge>

### 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`

## Approach

```mermaid
flowchart TD
  S(["frequencySort(nums)"]) --> F["freq: count every value in nums"]
  F --> C["sort nums with a two-key comparator"]
  C --> K1["primary: freq[a] - freq[b] — rarer first"]
  C --> K2["tie-break: b - a — larger value first"]
  K1 --> R(["return nums"])
  K2 --> R
```

## Solution

```js
/**
 * @param {number[]} nums
 * @return {number[]}
 */
var frequencySort = function (nums) {
  const freq = {};
  for (let n of nums) freq[n] = (freq[n] || 0) + 1;
  return nums.sort((a, b) => freq[a] - freq[b] || b - a);
};
```

## Explanation

<YouTube id="Evq1SfUbhBg" title="Sort Array by Increasing Frequency - Leetcode 1636 - Python" />