How to compare values in arrays and add the value from one array to another-CodePudding

I've got 2 arrays:

$array1 = ('1','2','7','9') $array2 = ('7','9','1','2')

These collections are dynamically changed and I need to add the values from the first array to second. I need to create a condition if.... and check... if these arrays are equals - do nothing.

But, if the first array has new value for example it becomes $array1 = ('1','2','7','9', '6') and second array doesn't have such value

then I need to add this '6' new value to the second array...so the second array will become $array2 = ('7','9','1','2', '6')... please help to achieve it.

Please note that values in 2 arrays could be in different order it doesn't matter, the goal is to have the same values inside 2 arrays.

CodePudding user response：

Merge the two and sort out non-unique values:

$array2 = @($array1;$array2) |Sort-Object -Unique

For large arrays you may want to add all items from both arrays to a HashSet instead - it'll only store distinct values, so the resulting set will correspond to the new value of $array2:

$set = [System.Collections.Generic.HashSet[psobject]]::new()
$array1 |% { [void]$set.Add($_) } 
$array2 |% { [void]$set.Add($_) } 

$array2 = @($set)

CodePudding user response：

If you want to retain the order in $array2 and append those elements (in order) from $array1 that aren't yet in $array2, you can use Compare-Object:

$array1 = '1','2','7','9','6'
$array2 = '7','9','1','2'

$array2  = 
  (Compare-Object -PassThru $array1 $array2 | Where-Object SideIndicator -eq  '<=')

Note: Compare-Object, like PowerShell in general, is case-insensitive by default; add -CaseSensitive if needed.

CodePudding user response：

You can use IsSupersetOf and UnionWith from HashSet<T>:

$array1 = [string[]] ('1','2','7','9','new value')
$array2 = [System.Collections.Generic.HashSet[string]] ('7','9','1','2')

if(-not $array2.IsSupersetOf($array1)) {
    $array2.UnionWith($array1)
}

$array2

In case you need to have an actual array back you can cast [object[]] or [string[]] back depending on your need:

[string[]] $array2

Worth mentioning that hashsets are case sensitive by default, in case you need a case-insensitive hashset you can instantiate it using a case-insensitive comparer:

$array2 = [System.Collections.Generic.HashSet[string]]::new(
    [string[]]('7','9','1','2'),
    [System.StringComparer]::OrdinalIgnoreCase
)

CodePudding user response：

You could build on top of this solution, by creating a function.

This code block lists array 1 and array 2 It uses the -notcontains cmdlet to check if the elements in array are in array2 and if not, then appends the element in array 2.

$array = @('1','2','7','9', '15') 
$array2 = @('1','2','7','9')

Write-Output "$array `n"

Write-Output "$array2 `n"

$array | ForEach-Object {
    if ($array2 -notcontains $_) {
        $array2  = $_
    }
}

Write-Output "$array2"

Hope this helps!