using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

public class Program

{

    public static void Main()

    {

        string s = "aA";

        StringBuilder sb = new StringBuilder();

        sb.Append(s);

        List<string> sbV= new List<string>();

        List<string> vowels = new List<string>();

        vowels.Add("a");

        vowels.Add("e");

        vowels.Add("i");

        vowels.Add("o");

        vowels.Add("u");

        vowels.Add("A");

        vowels.Add("E");

        vowels.Add("I");

        vowels.Add("O");

        vowels.Add("U");

        var i=s.Length-1;

        while(i>=0){

            if(vowels.Contains(s[i].ToString()))

            {

                sbV.Add(s[i].ToString());

            }

            i--;

        }

        //stack 寫法

        Stack<char> Vstack = new Stack<char>();

        foreach(var g in s)

        {

            if(vowels.Contains(g.ToString()))

            {

                Vstack.Push(g);

            }

        }

        StringBuilder sbStack = new StringBuilder();

        foreach(var g in s)

        {

            if(vowels.Contains(g.ToString()))

            {

                sbStack.Append(Vstack.Pop());

            }

            else

            {

                sbStack.Append(g);

            }

        }

        Console.WriteLine("sbStack:"+sbStack);

        //---Stack the end

        var q=0;

        for(var k=0 ; k<s.Length ;k++)

        {

            if(vowels.Contains(s[k].ToString()))

            {

                sb[k]=Convert.ToChar(sbV[q]);

                q++;

            }

        }

​

        //foreach(var j in sbV){

        //  Console.WriteLine(j);

        //}

        Console.WriteLine(sb);

    }

}