反转古诗

    class Program
    {
        static void Main(string[] args)
        {
            string input = "白日依山尽，黄河入海流。欲穷千里目，更上一层楼。";
            IStringInverter inverter1 = new StringInverter1();
            string str1 = inverter1.PiecewiseInvert(input);
            Console.WriteLine(str1);

            IStringInverter inverter2 = new StringInverter2();
            string str2 = inverter2.PiecewiseInvert(input);
            Console.WriteLine(str2);
            Console.Read();
        }

    }
    /// <summary>
    /// 根据标点符号反转
    /// </summary>
    class StringInverter1 : IStringInverter
    {
        #region IStringInverter 成员
        public string PiecewiseInvert(string input)
        {
            StringBuilder sb = new StringBuilder();
            int spindex = input.IndexOf('。');
            for (int i = 0; i < input.Length; i++)
            {
                if (spindex > -1)
                {
                    if (input[i] != '。')
                    {
                        sb.Append(input[spindex - i - 1]);
                    }
                    else
                    {
                        i -= (spindex + 1);
                        input = input.Remove(0, spindex + 1);
                        spindex = input.IndexOf('。');
                        sb.Append('。');
                    }
                }
                else
                {
                    sb.Append(input[input.Length - i - 1]);
                }//每句反转             
            }
            string[] two = sb.ToString().Split('。', '，');
            if (two.Length > 3)
                return two[1] + "，" + two[0] + "。" + two[3] + "，" + two[2] + "。";
            else
                throw new ArgumentException("此方法只能处理**，**。的语句");
        }

        #endregion
    }
    /// <summary>
    /// 利用正则，3种方法反转字符串
    /// </summary>
    class StringInverter2 : IStringInverter
    {
        #region IStringInverter 成员
        public string PiecewiseInvert(string input)
        {
            Regex punctuationReg = new Regex(@"[，。]");
            MatchCollection matchs = punctuationReg.Matches(input);
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < matchs.Count; i++)//匹配出有多少段
            {
                int index = input.IndexOf(matchs[i].Value);
                string section = input.Remove(index);
                input = input.Remove(0, index + 1);
                #region  遍历一半,利用临时变量
                var tempchars = section.ToCharArray();
                int templen = tempchars.Length;
                for (int c = 0; c < templen / 2; c++)
                {
                    char temp = tempchars[c];
                    tempchars[c] = tempchars[templen - c - 1];
                    tempchars[templen - c - 1] = temp;
                }
                section = string.Join("", tempchars);
                sb.Append(section);
                #endregion
                #region 遍历一遍
                //for (int c = 0; c < section.Length; c++)
                //{
                //    sb.Append(section[section.Length - c - 1]);//反转每句
                //}
                #endregion
                #region array的静态方法反转
                //var chars = section.ToCharArray();
                //Array.Reverse(chars);
                //section = string.Join("", chars);
                //sb.Append(section);
                #endregion
                sb.Append(matchs[i].Value);//加上标点
            }
            return sb.ToString();
        }
        #endregion
    }

    interface IStringInverter
    {
        string PiecewiseInvert(string input);
    }