求一高效算法! --实在搞不定了
情况说明:
  50000个字符串
  字符串是有特点的, 形如 "1,3,5,54,68,998,52,34,65"  只有数字和英文逗号
需求说明: 
  从这50000个字符串中提取出其中的数字,并去重(distinct),时间要求:普通PC机(酷睿双核2.5GHZ,2G内存)50ms以内,如果能进30ms,那就更好了
我的代码如下

    class Program

    {

        static void Main(string[] args)

        {

            while (true)

            {

                Stopwatch timer = new Stopwatch();

                timer.Reset();

                HashSet<string> ht = new HashSet<string>();              

                timer.Start();                

                for (int i = 0; i <= 50000; i++)

                {

                    string apps = "112,2,3,4,5,6,7,8,9,10,112,12,13,14,15,16,17,18,19,20,";



                    char[] appCharArr = apps.ToCharArray();

                    int length = appCharArr.Length;                   

                    int startIndex = 0;

                    char[] tempcharArr = new char[] { '\0', '\0', '\0', '\0' };

                    #region

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

                    {

                        char c = appCharArr[j];

                        if (c == ',')

                        {