"新的随机（X）"总是产生相同的号码？ [英] "new Random(x)" always generates the same numbers?

问题描述

我想获得一个唯一的随机数，但每次我运行代码的时候，我总是得到相同的号码。我会得到14首，然后6，但似乎我持有所有使用的号码列表并不work.adding 14手动工作，但是当我添加randInt这是行不通的。

  const int的numCards = 32; 
名单，LT; INT> usedCards =新的List< INT>（）; 
 INT randInt = 0; 
随机兰特=新的随机（numCards）; 
 usedCards.Add（14）; 
做
 {
 
 randInt = rand.Next（0，numCards）; 
 MessageBox.Show（randInt.ToString（），游戏结束，MessageBoxButtons.OK，MessageBoxIcon.Exclamation）; 
 
} 
，而（usedCards.Contains（randInt））; 
 
 usedCards.Add（randInt）; 
  

解决方案

替换为：

 随机兰特=新的随机（numCards）; 
  

与

 随机兰特=新的随机（）; 
  

供应一个的固定的种子值（ numCards 总是在 随机构造函数调用将导致的预测的可重复性的序列，始终是相同的种子值相同，就像这样（不完全，但还是点有效）：

例如使用 1 并提请10个数字，从0到100，我的机器的总是的生产序列

  24,11,46,77,65,43,35， 94,10,64 
  

使用，另一方面没有种子值，该序列变成不可预测的。

如果没有传递的种子值，随机将生成基于当前时间的新的种子值，那是什么你想获得的随机数的一个新的序列 - 只要你不快速订单重新初始化它，这就是为什么你应该重新使用随机实例，而不是重新创建他们每一次。

I am trying to get a unique random number but i always get the same number every time i run the code. i will get 14 first then 6 but my list for holding all the used numbers doesn't seem to work.adding the 14 manually works but when i add randInt it doesn't work.

const int numCards = 32;
        List<int> usedCards = new List<int>();
        int randInt = 0;
        Random rand = new Random(numCards);
        usedCards.Add(14);
        do
        {

            randInt = rand.Next(0, numCards);
            MessageBox.Show(randInt.ToString(), "End Game", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);

        }
        while (usedCards.Contains(randInt));

        usedCards.Add(randInt);

解决方案

Replace:

Random rand = new Random(numCards);

with

Random rand = new Random();

Supplying a fixed seed value (numCards always has the same value) in the Random constructor call will result in a predictable, reproducible sequence which is always the same for the same seed value, just like this (not quite but still the point is valid):

For example using a fixed seed of 1 and drawing 10 numbers ranging from 0 to 100, on my machine always produces the sequence

24,11,46,77,65,43,35,94,10,64

Using no seed value on the other hand, the sequence becomes unpredictable.

Without a seed value passed in, Random will generate a new seed value based on the current time, that's what you want to get a new sequence of random numbers - provided you don't initialize it again in fast order, that's why you should re-use Random instances instead of re-creating them every time.

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