Sort array by increasing frequency

Leetcode 1636 problem.

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.

Go

Time complexity: $O(n*log(n))$ - n is a length of an array
Auxiliary space: $O(n)$ - n is a length of an array

import (
    "sort"
)

func frequencySort(nums []int) []int {
    // key = number
    // value = frequency of this number in array
    frequencyMap := make(map[int]int)
    for _, num := range nums {
        frequencyMap[num]++
    }

    sort.Slice(nums, func(i, j int) bool {
        // comparing frequency of numbers from recorded frequency map
        if frequencyMap[nums[i]] == frequencyMap[nums[j]] {
            // increasing order
            return nums[i] > nums[j]
        }
        // decreasing order
        return frequencyMap[nums[i]] < frequencyMap[nums[j]]
    })

    return nums
}

thoughtbook

Sort array by increasing frequency

Go