private static string reverseWords(string str) {
     string[] words = Array.FindAll<string>(str.Split(
                      new char[] {' ','\t'}),
                      delegate(string s) {
                         return !String.IsNullOrEmpty(s); });
     int i = words.Length - 1;
     if (i < 0)
         return String.Empty;
     StringBuilder sb = new StringBuilder(words[i]);
     while (--i >= 0)
         sb.Append(' ').Append(words[i]);
     return sb.ToString();
 }