反转字符串

题目： Implement a function to reverts string like this : "This is a cat" => "sihT si a tac"
思路：1.题目要求单词的顺序不变，但是单词的字母要反转，首先考虑到栈的特性

　　　2.先实现单词的字母反转：把单词逐字分割，压入栈中，全部进栈后在pop出来

　　　3.保存单词，只需要将句子按空格分隔然后保存在数组中即可

        public static void RevertString()
        {
            string s = "This is a cat";
            string[] word = s.Split(' ');
            for (int i = 0; i < word.Count(); i++)
            {
                Stack<string> w = new Stack<string> ();
                foreach (var a in word[i])
                {                   
                    w.Push(a.ToString());
                }
                string top = w.Pop();
                while (top != string.Empty)
                {
                    Console.Write(top);
                    if (w.Count > 0)
                    {
                        top = w.Pop();
                    }
                    else break;
                }
                Console.Write(" ");
            }
            Console.WriteLine();
        }