如何生成多个数组的所有排列/组合? [英] How can I generate all permutations / combinations of multiple arrays?

问题描述

我的目标很简单，我正在尝试为数据库中的产品生成所有可能组合的列表.

My goal is simple, I am trying to generate a list of all possible combinations for a product in a database.

例如；产品选项如下

• 产品选项:颜色/值:红色、绿色、蓝色
• 产品选项:尺寸/值:小号、中号、大号、XL
• 产品选项:风格/价值观:男性、女性

我希望能够自动生成所有 3 个的每个组合:

I want to be able to auto generate every single combination of all 3:

Small, Red, Mens
Small, Green, Mens
Small, Blue, Mens
etc

无论我将 2、3、4 还是 5 个数组传递给它，我都需要该函数工作.

I need the function to work whether I pass 2,3,4 or 5 arrays into it.

我进行了大量研究并阅读了以下文章，但未能实现我的目标.

I've done quite a bit of research and came across the following articles but have been unable to accomplish my goal.

我找到的文章如下:

• 如何生成列表元素的组合<T>在 .NET 4.0 中
• vb .net 字符串排列.排列还是组合?

推荐答案

改编来自 Eric Lippert 的博客关于笛卡尔积:

Adapting code from Eric Lippert's blog on Cartesian products:

Private Function CartesianProduct(Of T)(ParamArray sequences As T()()) As T()()

    ' base case: 
    Dim result As IEnumerable(Of T()) = {New T() {}}
    For Each sequence As var In sequences
        Dim s = sequence
        ' don't close over the loop variable 
        ' recursive case: use SelectMany to build the new product out of the old one 
        result = From seq In result
                 From item In s
                 Select seq.Concat({item}).ToArray()
    Next
    Return result.ToArray()
End Function

用法:

Dim s1 As String() = New String() {"small", "med", "large", "XL"}
Dim s2 As String() = New String() {"red", "green", "blue"}
Dim s3 As String() = New String() {"Men", "Women"}

Dim ss As String()() = CartesianProduct(s1, s2, s3)

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