`/**  * 已知有个rand7()的函数，返回1到7随机自然数，让利用这个rand7()构造rand10() 随机1~10。  */ using System; using System.Collections.Generic; using System.Linq; using System.Text;  namespace ConsoleApplication1 {     class Program     {         static void Main(string[] args)         {             Rand10 rand10 = Rand10.GetInstance();             long total = 9999999;             //记录1~10的数产生的次数             int[] numArray = new int[10];             for (long i = 0; i < total; i++)             {                 int randomNumber = rand10.Next();                 numArray[randomNumber - 1]++;             }             //打印产生各数的概率             for (int i = 0; i < numArray.Length; i++)             {                 Console.WriteLine(string.Format("产生{0}的概率是:{1:0.00000}", i + 1, (Double)numArray[i] / total));             }             Console.ReadLine();         }     }     //1~7的随机数产生类     public class Rand7     {         private static Rand7 _rand7;         private readonly Random _random = new Random();         private  Rand7()         {            }         public static Rand7 GetInstance()         {             if(_rand7==null)             {                 _rand7 = new Rand7();             }             return _rand7;         }         //获得随机数         public int Next()         {             return _random.Next(1, 8);         }     }      //1~10的随机数产生类     public class Rand10     {          private static Rand10 rand10;          private Rand7 _rand7 = Rand7.GetInstance();         private  Rand10()         {          }         public static Rand10 GetInstance()         {             if(rand10==null)             {                 rand10 = new Rand10();             }             return rand10;         }         //获得随机数         public int Next()         {             int num;             //均匀产生1、 2 、3、4、5             while (true)             {                 num = _rand7.Next();                 if (num <= 5)                     break;             }              while (true)             {                 int n = _rand7.Next();                 if (n == 1)                     continue;                 //n大于4的数字有5、6、7，因为是由Rand7产生的，所以概率均匀                 if (n > 4)                 //因为num只可取值1、2、3、4、5并且取值概率均匀，num*2可得2、4、6、8、10也概率均匀                     num *= 2;                 //n小于4的数字有1、2、3，因为是由Rand7产生的，所以概率均匀                 else                 //因为num只可取值1、2、3、4、5并且取值概率均匀，num*2-1可得1、3、5、7、9也概率均匀                     num = num * 2 - 1;                 break;             }             return num;         }     } } `