范围内的非重复整数（不包括0）产生重复的整数序列

Question

参考generating random numbers without consecutive repetition，我想做一个不重复的随机整数生成器，但在2到9之间。

我充分利用了上述网址中答案的包装代码。

int oldrand = <prior random number>;
int adder = randomNumberGenerator() % 4;
int newrand = (oldrand + adder + 1) % 5;

不过，我的代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Random Rand = new Random();
            int oldrand = Rand.Next(0,7);
            //Console.WriteLine(oldrand);
            for (int i=0; i<50;i++) {

            int adder = Rand.Next(0,7) % 7;
            int newrand = (oldrand + adder + 1) % 8+2;
            int newrand2 = (newrand + adder + 1) % 8+2;
            int newrand3 = (newrand2 + adder + 1) % 8+2;
            int newrand4 = (newrand3 + adder + 1) % 8+2;

            Console.WriteLine(newrand);
            Console.WriteLine(newrand2);
            Console.WriteLine(newrand3);
            Console.WriteLine(newrand4);
            oldrand = newrand4;
            Console.WriteLine();
            }
        }
    }

    public class Rand {
        private static readonly Random globalRandom = new Random(); 
        private static readonly object globalLock = new object();

        private static readonly ThreadLocal<Random> threadRandom = new ThreadLocal<Random>(NewRandom);

        public static Random NewRandom() 
        { 
            lock (globalLock) 
            { 
                return new Random(globalRandom.Next()); 
            } 
        }

        public static Random Instance { get { return threadRandom.Value; } }

        public static int Next(int minValue, int maxValue) 
        { 
            return Instance.Next(minValue, maxValue); 
        }

    }
}

产生一个奇怪的结果：

2
7
4
9

2
3
4
5

2
7
4
9

5
9
5
9

8
7
6
5

3
9
7
5

2
7
4
9

5
9
5
9

5
9
5
9

9
9
9
9

5
9
5
9

7
5
3
9

8
7
6
5

3
9
7
5

9
5
9
5

4
3
2
9

6
3
8
5

2
7
4
9

6
3
8
5

9
5
9
5

如您所见，5 和 9 像一个模式一样重复，而在另一个序列中，您会看到所有四个 9。

Answer 1

您的代码的问题是您需要为每个想要的新随机数选择一个新的随机数。您的代码一遍又一遍地重复使用单个随机数，因此您只会得到一个数学上可预测的序列，并且根据您从哪里开始，您会得到重复。

这是一个有效的代码版本（并测试结果……它的编写方式我认为更具可读性、可重用性和可理解性）：

    static void Main(string[] args)
    {
        Random random = new Random();
        const int max = 8;

        for (int i = 0; i < 50; i++)
        {
            int[] sequence =
                GetRandomNonConsecutiveSequence(random, max, 4)
                .Select(j => j + 2)
                .ToArray();

            if (!CheckSequence(sequence))
            {
                Console.WriteLine("Sequence failed: " + string.Join(", ", sequence));
            }
        }
    }

    private static bool CheckSequence(int[] sequence)
    {
        int previous = sequence[0];

        for (int i = 1; i < sequence.Length; i++)
        {
            if (previous == sequence[i])
            {
                return false;
            }

            previous = sequence[i];
        }

        return true;
    }

    private static IEnumerable<int> GetRandomNonConsecutiveSequence(
        Random random, int max, int count)
    {
        int previous = random.Next(max);

        yield return previous;

        while (--count > 0)
        {
            yield return previous = Next(previous, max, random);
        }
    }

    static int Next(int previous, int max, Random random)
    {
        return (previous + random.Next(max - 1) + 1) % max;
    }