using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

//把字串裡的"母音"順序倒過來放

public class Program

{

    public static void Main()

    {

        string s = "leetcode";

        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");

        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);

    }

}