Question

如何将所有可能的组合写入控制台？例如，如果用户输入abc，那么它将写入aaa，aab，aac，abb，abc，acc，bbb，bbc，ccc。请帮帮我。

以下是一些代码：

    Dim abc() As String = {"a", "b", "c"} '      

    Sub Main()
        Console.WriteLine("Enter the amount of characters")
        Dim count As Integer = Console.ReadLine
        outputStrings("", count)

        Console.ReadLine()
    End Sub

    Private Sub outputStrings(ByVal startString As String, ByVal letterCount As Integer)
        For i = 0 To abc.Length - 1
            Dim temp As String = startString           
            temp += abc(i)
            If temp.Length = letterCount Then
                Console.WriteLine(temp)

                If i = abc.Length - 1 Then
                    Console.WriteLine("----")    
                End If
            Else
                outputStrings(temp, letterCount)
            End If

        Next
    End Sub

必须在虚线后删除不需要的排列以省略有效组合。

Answer 1

def go(chars,thusfar):
    if len(thusfar) = len(chars):
        print thusfar
    for char in chars:
        go(chars,thusfar+char);

这应该很容易转换为VB（阅读：我不知道VB）

Answer 2

您可以使用附加参数 abcIndex 将 abc（i）右侧或下方的字母限制为，并从那里开始for循环。只会写出按字母顺序排列字母的字符串，以防止重复。

Private Sub outputStrings(ByVal startString As String, ByVal letterCount As Integer, ByVal abcIndex As Integer)
    For i = abcIndex To abc.Length - 1
        Dim temp As String = startString
        temp += abc(i)
        If temp.Length = letterCount Then
            Console.WriteLine(temp)
        Else
            outputStrings(temp, letterCount, i)
        End If
    Next
End Sub

致电：

outputStrings("", 3, 0)

Answer 3

你只需要在那里进行递归调用。

Dim abc() As String = {"a", "b", "c"} '      

Sub Main()
    Console.WriteLine("Enter the amount of characters")
    Dim count As Integer = Console.ReadLine
    outputStrings("", count)

    Console.ReadLine()
End Sub

Private Sub outputStrings(ByVal startString As String, ByVal letterCount As Integer)
    For i = 0 To abc.Count - 1
        Dim temp As String = startString           
        temp += abc(i)
        If temp.Length = letterCount Then
            Console.WriteLine(temp)
        Else
            outputStrings(temp, letterCount)
        End If

    Next
End Sub

请注意，如果有人输入负数，您的代码将永久运行。我会把这个作为一个简单的练习。

Answer 4

来自here:的惊人代码

Private Shared Function PermutationsWithRepetition(Of T)(list As IEnumerable(Of T), length As Integer) As IEnumerable(Of IEnumerable(Of T))
        If length = 1 Then
            Return list.[Select](Function(x) New T() {x})
        End If
        Return PermutationsWithRepetition(list, length - 1).SelectMany(Function(x) list, Function(t1, t2) t1.Concat(New T() {t2}))
    End Function

可与Integer，Char，Double等一起使用使用示例：

Dim myarray(1) As Integer
myarray(0) = 1
myarray(1) = 2
Dim k As Integer = 2 'number of "slots" to do the permutations

mypermutations = PermutationsWithRepetition(myarray,k)

For Each row As IEnumerable(Of Integer) In mypermutations
            Console.WriteLine("")
            For Each col As IntegerIn row
                Console.Write(col.toString())
            Next            
Next

输出：

11 12 21 22

得到重复的组合

4 个答案: