Leetcode challenge 22/05/2020 https://leetcode.com/explore/challenge/card/may-leetcoding-challenge/537/week-4-may-22nd-may-28th/3337/

sort-characters-by-frequency.go

import (
	"sort"
	"strings"
)

func frequencySort(s string) string {
	abcfreq := make([]struct {
		chr rune
		cnt int
	}, 128)

	for _, r := range s {
		abcfreq[r].chr = r
		abcfreq[r].cnt++
	}

	sort.Slice(abcfreq, func(i int, j int) bool {
		return abcfreq[i].cnt > abcfreq[j].cnt
	})

	sorted := strings.Builder{}
	for _, val := range abcfreq {
		sorted.WriteString(strings.Repeat(string(val.chr), val.cnt))
	}

	return sorted.String()
}