Question

Randomise()
Dim questions(14) as string 
Dim picked questions(4) as string 
Dim rand as new random

Questions(0) = "?"
Questions(1) = "?"
...
Questions(14) = "?" 

For counter = 0 to 4
    Pickedquestions(counter) = questions(rand.next(0,15))
Next

我有一系列问题，我想从这一组中挑选5个问题。然而，我的方法意味着一些挑选的问题与我想避免的相同。我被建议使用排序算法对数组进行随机排序，然后选择第一个5.问题是我是初学者，我不明白如何将其合并到我的代码中。任何帮助或其他建议将不胜感激，谢谢。

Answer 1

这是来自here的Jon Skeet＆＃39; s Shuffle（）的VB.Net版本：

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Static rnd As New Random

        Dim questions(14) As String
        ' ...

        Dim PickedQuestions = questions.Shuffle(rnd).Take(4).ToArray()
        For i As Integer = 0 To PickedQuestions.Length - 1
            Debug.Print("PickedQuestions(" & i & ") = " & PickedQuestions(i))
        Next
    End Sub

End Class

Module Module1

    ' VB.Net Conversion of Jon Skeet's Shuffle() from: https://stackoverflow.com/a/1287572/2330053
    <System.Runtime.CompilerServices.Extension> _
    Public Iterator Function Shuffle(Of T)(source As IEnumerable(Of T), rng As Random) As IEnumerable(Of T)
        Dim elements As T() = source.ToArray()
        For i As Integer = elements.Length - 1 To 0 Step -1
            Dim swapIndex As Integer = rng.Next(i + 1)
            Yield elements(swapIndex)
            elements(swapIndex) = elements(i)
        Next
    End Function

End Module

好的......这里的东西多了一点......简单＆＃34;：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Static rnd As New Random

    Dim questions(14) As String
    For i As Integer = 0 To questions.Count - 1
        questions(i) = "Question " & i
    Next

    Dim tmpQuestions As New List(Of String)(questions)
    Dim PickedQuestions As New List(Of String)
    For i As Integer = 1 To 4
        Dim index As Integer = rnd.Next(tmpQuestions.Count)
        PickedQuestions.Add(tmpQuestions(index))
        tmpQuestions.RemoveAt(index)
    Next

    For i As Integer = 0 To PickedQuestions.Count - 1
        Debug.Print(i & ": " & PickedQuestions(i))
    Next
End Sub

Answer 2

随机播放questions数组并获取前四项。只需要一点Linq就可以了。

Imports System
Imports System.Linq

...

Dim questions(14) as string 

...

Dim rnd As New Random
Dim PickedQuestions = questions.OrderBy(Function() rnd.Next).Take(4).ToArray()

虽然简单而且相当直接，正如 Joel 所指出的那样，这不是最佳方法（但可能足以满足您的目的）。有关更好的排序算法，请参阅John Skeet's answer here。

停止正在重复的数组的一部分

2 个答案: