Overview

An input string is given. The objective is to sort the string based on frequency. We have to sort based on decreasing order of the frequency of characters. Let’s understand it with an example

Example 1

Input: "bcabcb"
Output: "bbbcca"

Example 2

Input: "mniff"
Output: "ffmni"

Program

Below is the program for the same

package main

import (
	"fmt"
	"sort"
)

func frequencySort(s string) string {
	stringMap := make(map[byte]int)
	lenS := len(s)
	for i := 0; i < lenS; i++ {
		stringMap[s[i]]++
	}

	itemArray := make([]item, 0)

	for key, value := range stringMap {
		i := item{
			char:      key,
			frequency: value,
		}
		itemArray = append(itemArray, i)
	}

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

	output := ""

	for i := 0; i < len(itemArray); i++ {
		for j := 0; j < itemArray[i].frequency; j++ {
			output = output + string(itemArray[i].char)
		}
	}

	return output

}

type item struct {
	char      byte
	frequency int
}

func main() {
	output := frequencySort("bcabcb")
	fmt.Println(output)

	output = frequencySort("mniff")
	fmt.Println(output)

}

Output:

bbbcca
ffmni

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