关于-c#字符串三种逆转方法及性能比较的另外看法

原文：c#字符串三种逆转方法及性能比较

看到后觉得很奇怪，个人认为在很多情况下类库方法肯定要比自己写的方法性能好

原文作者传入的字符串，如果是传入字符数组的话测试结果则大大出乎作者的意外。
修改代码如下：

 class StringReverse

    {

        /// <summary>

        /// 字符串逆转-StringBuilder实现

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public static string ReverseUsingStringBuilder(char[] str)

        {

            int length = str.Length;

            StringBuilder sb = new StringBuilder(length);



            for (int i = length - 1; i >= 0; i--)

            {

                sb.Append(str[i]);

            }

            return sb.ToString();

        }



        /// <summary>

        /// 字符串逆转-CharArray实现

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public static string ReverseUsingCharArray(char[] str)

        {

            char[] arr = str;

            Array.Reverse(arr);

            return new string(arr);

           // return string.Join(string.Empty,str.Reverse());

          

        }

        /// <summary>

        /// 字符串逆转-异或实现

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public static string ReverseUsingXor(char[] str)

        {

            char[] arr = str;

            int l = arr.Length-1;



            //交换值

            for (int i = 0; i < l; i++, l--)

            {

                str[i] ^= str[l];

                str[l] ^= str[i];

                str[i] ^= str[l];

            }

            return new string(str);

        }

        public delegate string funcDelegate(char[] s);



        /// <summary>

        /// 测试方法

        /// </summary>

        /// <param name="description">方法描述</param>

        /// <param name="func">测试方法</param>

        /// <param name="times">执行次数</param>

        /// <param name="str">测试字符串</param>

        public static void Benchmark(string description, funcDelegate func, int times, char[] str)

        {

            Stopwatch sw = new Stopwatch();

            sw.Start();

            for (int j = 0; j < times; j++)

            {

                func(str);

            }

            sw.Stop();

            Console.WriteLine("方法{0}：调用{1}次,用时{2}.", description, times, sw.ElapsedTicks);

        }

        /// <summary>

        /// 生成指定长度随机字符串

        /// </summary>

        /// <param name="length">字条串长度</param>

        /// <returns></returns>

        public static char[] RandomString(int length)

        {

            Random random = new Random();

           // StringBuilder sb = new StringBuilder();

            char[] sb=new char[length];

            for (int i = 0; i < length; i++)

            {

                sb[i]=Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));

            }

            return sb;

        }

        static void Main(string[] args)

        {

            int[] lengths = new int[] { 1, 10, 15, 25, 50, 75, 100, 1000, 100000 };

          //  int[] lengths = new int[] { 1, 10, 15, 25, 50, 75, 100};



            foreach (int len in lengths)

            {

                //每个方法都执行10000次，力求精确

                int iterations = 10000;



                //生成随机测试字符串

                char[] testString = StringReverse.RandomString(len);

          

                //打印测试信息

                StringReverse.Benchmark(String.Format("String Builder (测试字符串长度为{0})", len), StringReverse.ReverseUsingStringBuilder, iterations, testString);

                StringReverse.Benchmark(String.Format("Array.Reverse (测试字符串长度为{0})", len), StringReverse.ReverseUsingCharArray, iterations, testString);

                StringReverse.Benchmark(String.Format("Xor (测试字符串长度为{0})", len), StringReverse.ReverseUsingXor, iterations, testString);



                Console.WriteLine();

            }

            Console.Read();



        }

    }

　　测试结果截图：