不用额外字符串存储空间将句子中的每个单词倒叙

        public static string Reverse(char[] inputString)
        {
            int left = 0;
            int right = -1;
            int currentIndex = 0;

            if (inputString.Length <= 0)
                throw new ArgumentNullException("inputString", "input null exception occured");

            for (; currentIndex < inputString.Length; currentIndex++)
            {
                if (inputString[currentIndex] != ' ')
                {
                    right++;
                }

                while (((inputString[currentIndex] == ' '|| inputString.Length - 1 == currentIndex) && left <= right))
                {
                    Swap(ref inputString[left++], ref inputString[right--]);
                }

                if (inputString[currentIndex] == ' ')
                {
                    left = currentIndex + 1;
                    right = currentIndex;
                }
            }

            return inputString.ToString();
        }

        public static void Swap(ref char a, ref char b)
        { 
            char temp = a;
            a = b;
            b = temp;
        }

今天写了一下。感觉还有待优化。先贴出来。