/*

Given a string s, sort it in decreasing order based on the frequency of the characters. The frequency of a character is the number of times it appears in the string.

​

Return the sorted string. If there are multiple answers, return any of them.

​

Example 1:

​

Input: s = "tree"

Output: "eert"

Explanation: 'e' appears twice while 'r' and 't' both appear once.

So 'e' must appear before both 'r' and 't'. Therefore "eetr" is also a valid answer.

Example 2:

​

Input: s = "cccaaa"

Output: "aaaccc"

Explanation: Both 'c' and 'a' appear three times, so both "cccaaa" and "aaaccc" are valid answers.

Note that "cacaca" is incorrect, as the same characters must be together.

Example 3:

​

Input: s = "Aabb"

Output: "bbAa"

Explanation: "bbaA" is also a valid answer, but "Aabb" is incorrect.

Note that 'A' and 'a' are treated as two different characters.

*/

​

using System;

public class Program

{

    public static void Main()

    {

        string word = "hello world";

        ReverseString(word.ToCharArray());

    }

    public static void ReverseString(char[] word)

    {

        int length = word.Length - 1;

        string reverse = "";

        while(length > 0)

        {

            reverse = reverse + word[length];

            length--;

        }

        Console.WriteLine(reverse);

    }

    public string FrequencySort(string s) 

    {

        return string.Empty;

    }

}