随机数但不重复

Question

我想生成一个小于 50 的随机数，但一旦生成该数字，我希望它不能再次生成。

谢谢您的帮助！

Answer 1

请参阅：Fisher-Yates 洗牌：

public static void shuffle (int[] array) 
{
    Random rng = new Random();       // i.e., java.util.Random.
    int n = array.length;            // The number of items left to shuffle (loop invariant).
    while (n > 1) 
    {
        n--;                         // n is now the last pertinent index
        int k = rng.nextInt(n + 1);  // 0 <= k <= n.
        int tmp = array[k];
        array[k] = array[n];
        array[n] = tmp;
    }
}

Answer 2

将数字1-49放入可排序集合中，然后按随机顺序排序； 根据需要从集合中弹出每一个。

Answer 3

鉴于问题被标记为 VB/VB.Net...这是 Mitch 答案的 VB 实现。

Public Class Utils

   Public Shared Sub ShuffleArray(ByVal items() As Integer)

      Dim ptr As Integer
      Dim alt As Integer
      Dim tmp As Integer
      Dim rnd As New Random()

      ptr = items.Length

      Do While ptr > 1
         ptr -= 1
         alt = rnd.Next(ptr - 1)
         tmp = items(alt)
         items(alt) = items(ptr)
         items(ptr) = tmp
      Loop

   End Sub

End Class

Answer 4

下面的代码生成字母数字字符串，其长度作为参数传递。

Public Shared Function GetRandomAlphaNumericString(ByVal intStringLength As Integer) As String

Dim chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

Dim intLength As Integer = intStringLength - 1

Dim stringChars = New Char(intLength) {}

Dim random = New Random()

    For i As Integer = 0 To stringChars.Length - 1
        stringChars(i) = chars(random.[Next](chars.Length))
    Next

    Dim finalString = New [String](stringChars)
    Return finalString
End Function