arrays - 获取数组的所有组合

Question

我目前正在尝试制作一个函数，该函数获取数组值的所有可能组合。

我想出了一个非函数版本，但它限制为3个值，所以我正尝试使它的功能变得更加Dynamic
我试着搜索SO，但是找不到我想做的powershell示例，我可以找到一个PHP版本，但是我的PHP非常有限

PHP: How to get all possible combinations of 1D array?

非功能脚本

$name = 'First','Middle','Last'

$list = @()

foreach ($c1 in $name) {
    foreach ($c2 in $name) {
        foreach ($c3 in $name) {
            if (($c1 -ne $c2) -and ($c2 -ne $c3) -and ($c3 -ne $c1))
            {
                $list += "$c1 $c2 $c3"
            }
        }
    }
} 

这给我结果

First Middle Last
First Last Middle
Middle First Last
Middle Last First
Last First Middle
Last Middle First

我不确定在递归该函数时如何重新排列值，这是我到目前为止的结果:

<#
.Synopsis
    Short description
.DESCRIPTION
    Long description
.EXAMPLE
    Example of how to use this cmdlet
.EXAMPLE
    Another example of how to use this cmdlet
#>
function Get-Combinations
{
    [CmdletBinding()]
    [OutputType([int])]
    Param
    (
        # Param1 help description
        [Parameter(Mandatory=$true,
                   ValueFromPipelineByPropertyName=$true,
                   Position=0)]
        [string[]]$Array,

        # Param1 help description
        [Parameter(Mandatory=$false,
                   ValueFromPipelineByPropertyName=$false,
                   Position=1)]
        [string]$Temp,

        # Param1 help description
        [Parameter(Mandatory=$false,
                   ValueFromPipelineByPropertyName=$true,
                   Position=2)]
        [string[]]$Return
    )

    Begin
    {
        Write-Verbose "Starting Function Get-Combinations with parameters `n`n$($Array | Out-String)`n$temp`n`n$($Return | Out-String)"

        If ($Temp)
        {
            $Return = $Temp
        }

        $newArray = new-object system.collections.arraylist
    }
    Process
    {
        Write-Verbose ($return | Out-String)

        For($i=0; $i -lt $Array.Length; $i++)
        {
            #Write-Verbose $i

            $Array | ForEach-Object {$newArray.Add($_)}
            $newArray.RemoveAt($i)

            Write-Verbose ($newArray | Out-String)

            if ($newArray.Count -le 1)
            {
                Get-Combinations -Array $newArray -Temp $Temp -Return $Return
            }
            else
            {
                $Return = $Temp
            }
        }
        $newArray
    }
    End
    {
        Write-Verbose "Exiting Function Get-Combinations"
    }
}

$combinations = @("First","First2","Middle","Last")

$Combos = Get-Combinations -Array $combinations

$Combos

但是我得到的输出无处不在

First2
Last
First2
Last
First
First2
Middle
Last
First
First2
Middle
Last

28/08更新

越来越近，但输出仍然很奇怪

<#
.Synopsis
    Short description
.DESCRIPTION
    Long description
.EXAMPLE
    Example of how to use this cmdlet
.EXAMPLE
    Another example of how to use this cmdlet
#>
function Get-Combinations
{
    [CmdletBinding()]
    [OutputType([int])]
    Param
    (
        # Param1 help description
        [Parameter(Mandatory=$true,
                    ValueFromPipelineByPropertyName=$true,
                    Position=0)]
        [string[]]$Array,

        # Param1 help description
        [Parameter(Mandatory=$false,
                    ValueFromPipelineByPropertyName=$false,
                    Position=1)]
        [string]$Temp,

        # Param1 help description
        [Parameter(Mandatory=$false,
                    ValueFromPipelineByPropertyName=$true,
                    Position=2)]
        [string[]]$Return
    )

    Begin
    {
        Write-Verbose "Starting Function Get-Combinations with parameters `n`n$($Array | Out-String)`n$temp`n`n$($Return | Out-String)"

        If ($Temp)
        {
            $Return += $Temp
        }

        #$newArray = new-object [System.Collections.ArrayList]
        #$Array | ForEach-Object {$newArray.Add($_) | Out-Null}

        [System.Collections.ArrayList]$newArray = $Array
    }
    Process
    {
        Write-Verbose "return -> $return"

        For($i=0; $i -lt $Array.Length; $i++)
        {
            Write-Verbose "`$i -> $i"

            $element = $newArray[0]
            $newArray.RemoveAt(0)

            Write-Verbose "`$newArray -> $newArray"
            Write-Verbose "Element -> $element"

            if ($newArray.Count -gt 0)
            {
                Get-Combinations -Array $newArray -Temp (($temp + " " +$element).Trim()) -Return $Return
            }
            else
            {
                $Return = $Temp + " " + $element
            }
        }
        $return
    }
    End
    {
        Write-Verbose "Exiting Function Get-Combinations"
    }
}

$combinations = @("First","First2","Middle","Last")

$return = @()

$Combos = Get-Combinations -Array $combinations -Return $return

$Combos

新输出(是，“Last”值前有一个空格，不，我不知道为什么)

First First2 Middle Last
First First2 Last
First Middle Last
First Last
First2 Middle Last
First2 Last
Middle Last
 Last

Answer 1

这是我的解决方案:

function Remove ($element, $list)
{
    $newList = @()
    $list | % { if ($_ -ne $element) { $newList += $_} }

    return $newList
}


function Append ($head, $tail)
{
    if ($tail.Count -eq 0)
        { return ,$head }

    $result =  @()

    $tail | %{
        $newList = ,$head
        $_ | %{ $newList += $_ }
        $result += ,$newList
    }

    return $result
}


function Permute ($list)
{
    if ($list.Count -eq 0)
        { return @() }

    $list | %{
        $permutations = Permute (Remove $_ $list)
        return Append $_ $permutations
    }
}

cls

$list = "x", "y", "z", "t", "v"

$permutations = Permute $list


$permutations | %{
    Write-Host ([string]::Join(", ", $_))
}

编辑:同一功能(置换)相同。这有点作弊，但是由于我替换了lambdas的普通函数。您可以用自己处理的堆栈替换递归调用，但这会使代码不必要地变得复杂...

function Permute ($list)
{
    $global:remove = { 
        param ($element, $list) 

        $newList = @() 
        $list | % { if ($_ -ne $element) { $newList += $_} }  

        return $newList 
    }

    $global:append = {
        param ($head, $tail)

        if ($tail.Count -eq 0)
            { return ,$head }

        $result =  @()

        $tail | %{
            $newList = ,$head
            $_ | %{ $newList += $_ }
            $result += ,$newList
        }

        return $result
    }

    if ($list.Count -eq 0)
        { return @() }

    $list | %{
        $permutations = Permute ($remove.Invoke($_, $list))
        return $append.Invoke($_, $permutations)
    }
}

cls

$list = "x", "y", "z", "t"

$permutations = Permute $list

$permutations | %{
    Write-Host ([string]::Join(", ", $_))
}