PowerShell：兩個以上陣列的交集-有解無憂

使用 PowerShell，我有 14 個字串陣列。一些陣列是空的。如何獲得這些陣列（不包括空陣列）的交集（所有陣列中存在的所有元素）？我試圖避免一次比較兩個陣列。

有些陣列是空的，所以我不想在我的比較中包括這些。關于我將如何解決這個問題的任何想法？謝謝你。

$a = @('hjiejnfnfsd','test','huiwe','test2')
$b = @('test','jnfijweofnew','test2')
$c = @('njwifqbfiwej','test','jnfijweofnew','test2')
$d = @('bhfeukefwgu','test','dasdwdv','test2','hfuweihfei')
$e = @('test','ddwadfedgnh','test2')
$f = @('test','test2')
$g = @('test','bjiewbnefw','test2')
$h = @('uie287278hfjf','test','huiwhiwe','test2')
$i = @()
$j = @()
$k = @('jireohngi','test','gu7y8732hbj','test2')
$l = @()
$m = @('test','test2')
$n = @('test','test2')

我嘗試解決這個問題（盡管它不檢查空陣列）：

$overlap = Compare-Object $a $b -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $c -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $d -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $e -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $f -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $g -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $h -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $i -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $j -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $k -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $l -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $m -PassThru -IncludeEqual -ExcludeDifferent
$overlap = Compare-Object $overlap $n -PassThru -IncludeEqual -ExcludeDifferent

我想要的結果是 test 和 test2 出現在 $overlap 中。此解決方案不起作用，因為它不檢查它正在比較的陣列是否為空。

uj5u.com熱心網友回復：

注意：以下假設沒有單個陣列多次包含相同的字串（需要做更多的作業來解決這個問題）。

$a = @('hjiejnfnfsd','test','huiwe','test2')
$b = @('test','jnfijweofnew','test2')
$c = @('njwifqbfiwej','test','jnfijweofnew','test2')
$d = @('bhfeukefwgu','test','dasdwdv','test2','hfuweihfei')
$e = @('test','ddwadfedgnh','test2')
$f = @('test','test2')
$g = @('test','bjiewbnefw','test2')
$h = @('uie287278hfjf','test','huiwhiwe','test2')
$i = @()
$j = @()
$k = @('jireohngi','test','gu7y8732hbj','test2')
$l = @()
$m = @('test','test2')
$n = @('test','test2')

$allArrays = $a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n

# Initialize a hashtable in which we'll keep
# track of unique strings and how often they occur.
$ht = @{}

# Loop over all arrays.
$nonEmptyArrayCount = 0
foreach ($arr in $allArrays) {
  # Loop over each non-empty array's elements.
  if ($arr.Count -gt 0) {
      $nonEmptyArrayCount 
    foreach ($el in $arr) {
      # Add each string and increment its occurrence count.
      $ht[$el]  = 1
    }
  }
}

# Output all strings that occurred in every non-empty array
$ht.GetEnumerator() |
  Where-Object Value -eq $nonEmptyArrayCount |
  ForEach-Object Key

以上輸出所有非空輸入陣列中存在的那些字串：

test2
test

uj5u.com熱心網友回復：

你很近。從比較中排除空陣列是必不可少的，因為空陣列和任何其他陣列的交集是一個空陣列，并且一旦$overlap包含一個空陣列，無論后續陣列包含什么，它將成為最終結果。

這是帶有非空檢查并使用回圈重寫的代碼...

$a = @('hjiejnfnfsd', 'test', 'huiwe', 'test2')
$b = @('test', 'jnfijweofnew', 'test2')
$c = @('njwifqbfiwej', 'test', 'jnfijweofnew', 'test2')
$d = @('bhfeukefwgu', 'test', 'dasdwdv', 'test2', 'hfuweihfei')
$e = @('test', 'ddwadfedgnh', 'test2')
$f = @('test', 'test2')
$g = @('test', 'bjiewbnefw', 'test2')
$h = @('uie287278hfjf', 'test', 'huiwhiwe', 'test2')
$i = @()
$j = @()
$k = @('jireohngi', 'test', 'gu7y8732hbj', 'test2')
$l = @()
$m = @('test', 'test2')
$n = @('test', 'test2')

# Create an array of arrays $a through $n
$arrays = @(
    # 'a'..'n' doesn't work in Windows PowerShell
    # Define both ends of the range...
    #             'a'    → [String]
    #             'a'[0] → [Char]
    #     [Int32] 'a'[0] → 97 (ASCII a)
    # ...and cast each element back to a [Char]
    [Char[]] ([Int32] 'a'[0]..[Int32] 'n'[0]) |
        Get-Variable -ValueOnly
)

# Initialize $overlap to the first non-empty array
for ($initialOverlapIndex = 0; $initialOverlapIndex -lt $arrays.Length; $initialOverlapIndex  )
{
    if ($arrays[$initialOverlapIndex].Length -gt 0)
    {
        break;
    }
}
<#
    Alternative:
        $initialOverlapIndex = [Array]::FindIndex(
            $arrays,
            [Predicate[Array]] { param($array) $array.Length -gt 0 }
        )
#>
$overlap = $arrays[$initialOverlapIndex]

for ($comparisonIndex = $initialOverlapIndex   1; $comparisonIndex -lt $arrays.Length; $comparisonIndex  )
# Alternative: foreach ($array in $arrays | Select-Object -Skip $initialOverlapIndex)
{
    $array = $arrays[$comparisonIndex]
    if ($array.Length -gt 0)
    {
        $overlap = Compare-Object $overlap $array -PassThru -IncludeEqual -ExcludeDifferent
    }
}

$overlap

...輸出...

test
test2

uj5u.com熱心網友回復：

這是一個使用Hashset. A是一個只存盤唯一項并提供快速查找Hashset的集合，這使其成為交集計算的不錯選擇。它甚至有一個接受任何可列舉型別（例如陣列）作為引數的方法。該方法修改了原始方法，使其僅包含傳遞給該方法的引數和引數中包含的元素。IntersectWithHashsetHashset

# Test input
$a = @()     # I changed this to empty array for demonstration purposes
$b = @('test','jnfijweofnew','test2')
$c = @('njwifqbfiwej','test','jnfijweofnew','test2')
$d = @('bhfeukefwgu','test','dasdwdv','test2','hfuweihfei')
$e = @('test','ddwadfedgnh','test2')
$f = @('test','test2')
$g = @('test','bjiewbnefw','test2')
$h = @('uie287278hfjf','test','huiwhiwe','test2')
$i = @()
$j = @()
$k = @('jireohngi','test','gu7y8732hbj','test2')
$l = @()
$m = @('test','test2')
$n = @('test','test2')

# Create a variable with a type-constraint
[Collections.Generic.Hashset[object]] $overlap = $null

# For each of the arrays...
($a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n).
    Where{ $_.Count -gt 0 }.           #... except the empty ones
    ForEach{
        # If the Hashset has not been initialized yet
        if( $null -eq $overlap ) {
            # Create the initial hashset from the first non-empty array.
            $overlap = $_
        }
        else { 
            # Hashset is already initialized, calculate the intersection with next non-empty array.
            $overlap.IntersectWith( $_ )
        }
    }

$overlap  # Output

輸出：

test
test2

評論：

為了過濾掉空陣列（或者一般來說任何型別的集合），我們檢查它的Count成員，它給出了元素的數量。

.Foreach并且.Where是 PowerShell內在方法。這些可能比ForEach-ObjectandWhere-Object命令更快，尤其是在直接使用集合時（而不是另一個命令的輸出）。像往常一樣，自動變數$_表示集合的當前元素。

這段使用管道命令的代碼在功能上是相同的：

[Collections.Generic.Hashset[object]] $overlap = $null

$a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n |
    Where-Object Count -gt 0 |           
    ForEach-Object{
        if( $null -eq $overlap ) {  
            $overlap = $_ 
        }
        else { 
            $overlap.IntersectWith( $_ )   
        }
    }

在操作員的左側if( $null -eq $overlap )非常重要。如果它在右側，PowerShell 將與過濾元素進行元素比較，而不是檢查變數本身是否是（請參閱關于比較運算子）$null-eq$null$overlap$null
在這一行中，$overlap = $_PowerShell 自動將當前陣列轉換為 a Hashset，因為我們使用before設定了型別約束并且可以轉換為（請參閱關于變數）。[Collections.Generic.Hashset[object]] $overlaparrayHashset

默認情況下，a 的字串比較Hashset區分大小寫。要使其不區分大小寫，請將每個字串轉換為小寫，如下所示：

[Collections.Generic.Hashset[object]] $overlap = $null

($a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n).
    Where{ $_.Count -gt 0 }.
    ForEach{
        if( $null -eq $overlap ) {
            $overlap = $_.ToLower()
        }
        else { 
            $overlap.IntersectWith( $_.ToLower() )
        }
    }

這使用成員訪問列舉來呼叫String.ToLower()輸入陣列的每個元素的方法。

對于第一個變體，在and之前插入換行符并不是必需的，但可以提高代碼的可讀性（請注意，您不能在and之前插入換行符，因為這會使 PowerShell 決議器感到困惑）。WhereForEach .Where.ForEach

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標籤：数组电源外壳交集

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