Uppercase Words

Uppercase Words

using System;
using System.Linq;
using System.Security;
using System.Text;
using System.Text.RegularExpressions;

public class UppercaseWords
{
    public static void Main()
    {
        const string UppercaseWordPattern = @"(?<![a-zA-Z])[A-Z]+(?![a-zA-Z])";
        Regex regex = new Regex(UppercaseWordPattern);

        string input = Console.ReadLine();

        while (input != "END")
        {
            var words = regex.Matches(input);

            foreach (Match match in words)
            {
                string word = match.ToString();
                int index = match.Index;

                var replacement = IsPalindrome(word) ? GetRepeatedWord(word) : GetReversedWord(word);

                Regex replacementRegex = new Regex(word);
                input = replacementRegex.Replace(input, replacement, 1, index);
            }

            Console.WriteLine(SecurityElement.Escape(input));

            input = Console.ReadLine();
        }
    }

    private static string GetReversedWord(string word)
    {
       return new string(word.ToCharArray().Reverse().ToArray());
    }

    private static string GetRepeatedWord(string word)
    {
        StringBuilder result = new StringBuilder(2 * word.Length);

        foreach (var symbol in word)
        {
            result.AppendFormat("{0}{0}", symbol);
        }

        return result.ToString();
    }

    private static bool IsPalindrome(string word)
    {
        string reversedWord = GetReversedWord(word);

        return reversedWord == word;
    }
}