以前的老代码翻出来看，还是喜欢以前写的，精练些。

 

static void Main(string[] args)        {            int[] a = { 32, 324, 645, 856, 3, 56, 8, 6, 4, 368, 87, 55, 78, 434, 12, 345, 787, 90, 123, 304, 90 };            int bit = 3;            Foo(a, bit);            for (int i = 0; i < a.Length; i++)            {                Console.Write("{0}  ", a[i]);            }            Console.Read();        }        private static void Foo(int[] a, int bit)        {            List
      
       [] t = new List
       
        [10];            for (int i = 0; i < 10; i++)            {                t[i] = new List
        
         ();            }            while (bit > 0)            {                for (int i = 0; i < a.Length; i++)                {                    //这里比较重要， 数%10^x/10^(x-1)                    t[a[i] % ((int)Math.Pow(10, 4 - bit)) / ((int)Math.Pow(10, (3 - bit)))].Add(a[i]);                }                Proc(t, a);                bit--;            }        }        static void Proc(List
         
          [] t, int[] a)        {            int x = 0;            for (int i = 0; i < t.Length; i++)            {                foreach (int l in t[i])                {                    a[x++] = l;                }            }            for (int i = 0; i < 10; i++)            {                t[i] = new List
          
           ();            }        }