算法挑战 36进制条码序列号生成器[修正]

问题描述：
条码打印.要求是唯一的序列.中间有一个日期,最后3位为流水号.但打印的张数会超过999;
因此必须用到26个大写字母,用36进制的话3位可以表示36*36*36=46656个数字。
现在要求如下：
999以前就是普通数字(001~999),再多就开始在百位使用字母
即999的后一个数字为A00此时十位和个位还不能使用字母(平时打印会少于3600张,为了客户看起来方便),
只有在百位将Z用完后才允许在十位使用字母,十位用完才允许个位使用字母
注意事项:
1)不能重复
2)数字个数应达到46656个
3)效率不能太低
4)请在本地测试没有重复序列号
博客： http://www.cnblogs.com/shinn/archive/2008/04/22/1147473.html 给了算法思路，但他的代码有问题。
我的分析：

 

我的代码：

/*

 * Created by SharpDevelop.

 * User: liuyk

 * Date: 2009-9-22

 * Time: 22:05

 */

using System;

namespace ConvertTo36X

{

    /// <summary>

    /// 把[0-46655]转换成36进制的3位序列.

    /// </summary>

    public class ConvertTo36X

    {

        private readonly char[] Char26=new char[]{'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

        private readonly char[] Char36=new char[]{'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

        public string ConvertNum(int num)

        {

        if(num<0 || num>46655)

        {

        throw new Exception("输入的数字超出范围");

        }

        else if(num>=12960)

        {

        string value="";

        num-=12960;

        char h=Char36[((int) (num/936))%36];

        char t=Char36[((int) (num/26))%36];

        char d=Char26[num%26];

        return value+h+t+d;

        }

        else if(num>=3600)

        {

        string value="";

        num-=3600;

        char h=Char36[(int)((num%360)/10)];

        char t=Char26[(int)(num/360)];

        int d=num%10;

        return value+h+t+d;

        }

        else if(num>=10)

        {

        string value="";

        char h=Char36[(int)(num/100)];

        num=num%100;

        int t=(int)(num/10);

        int d=num%10;

        return value+h+t+d;

        }

        else

        {

        return "00"+num;

        }

        }

    }

 }

/*

 * Created by SharpDevelop.

 * User: liuyk

 * Date: 2009-9-24

 * Time: 17:09

 * 

 * To change this template use Tools | Options | Coding | Edit Standard Headers.

 */

using System;

using   System.IO;   

namespace ConvertTo36X

{

    class TestConvertTo36

    {

        public static void Main(string[] args)

        {

            Console.WriteLine("Hello World!");

            // TODO: Implement Functionality Here

                        ConvertTo36X xx=new ConvertTo36X();

            FileStream   fileName  =   new   FileStream("Temp.txt",FileMode.OpenOrCreate);  

            StreamWriter sw = new StreamWriter(fileName);

            //System.Console.WriteLine(xx.ConvertNum(46655));

        for (int j=0;j<=46655;j++){

            System.Console.WriteLine(j);

            sw.WriteLine(xx.ConvertNum(j)); 

        }

            sw.Close();

            Console.Write("Press any key to continue . . . ");

            Console.ReadKey(true);

        }

    }

}