一道腾讯面试题

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/**
* 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 == 4)
                    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
                  &

补充：软件开发 , C# ,