[英]Scala Random Number Generator Not Producing Unique Random Numbers Between A Range
I have the following code to generate new random numbers 我有以下代码来生成新的随机数
val start = 1
val end = 50000000
val rnd = new scala.util.Random
for (i < 1 to 25000000){
val rnum = start + rnd.nextInt((end - start) + 1)
...
}
But this is producing duplicate random numbers now and again. 但是,这一次又一次地产生重复的随机数。 Is this a bug or have I done something stupid?
这是错误还是我做了一些愚蠢的事情?
Don't worry, this is not a bug, and you have not done anything stupid. 不用担心,这不是错误,您也没有做任何愚蠢的事情。 However you have missed the fact that a sequence of random numbers can contain duplicates .
但是,您已经错过了一个事实,即随机数序列可以包含重复项 。
The reasons are explained in the comments. 注释中说明了原因。
The problem is that humans don't have a good instinctive understanding of random numbers. 问题在于人类对随机数没有很好的本能理解。 If you ask people to write a series of digits they are very unlikely to repeat a digit, even though this should happen 10% of the time.
如果您要求人们写一系列数字,即使出现这种情况的可能性为10%,他们也不大可能重复一个数字。 If you ask people to write down 5 random digits they are unlikely to use the same digit twice, even though this should happen 70% of the time.
如果您要求人们写下5个随机数字,那么即使70%的情况下,他们都不太可能两次使用相同的数字。
There is no bug. 没有错误。 It selects randomly so chances are there that same element would be picked.
它随机选择,因此有机会选择相同的元素。 I prefer using the shuffle function of List.
我更喜欢使用List的shuffle功能。
val list = (1 to 100).toList
scala.util.Random.shuffle(list).take(1)
But creating a list of big number won't be an effective solution. 但是创建大量列表将不是一个有效的解决方案。 You can use the following way to generate a random number.
您可以使用以下方式生成随机数。
val seed = new java.util.Date().hashCode
val rand = new scala.util.Random(seed)
val someNum = rand.nextInt
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