CODEWITHSUNDEEP
powershell
Kumar
Kumar

Reputation: 21

powershell comparing multiple arrays

I've a case where multiple arrays need to be compared.There is one master array that contains all the elements that the child arrays have and also some extra elements.

In below example, $a is the master array and $b, $c are child arrays. I need to compare these arrays and get the list of those extra elements in $a that are not present in $b and $c. Practically, in my case there are 10 child arrays and a master array.

$a="dhaw","roh","kohl","faf","abd","steyn","gupt","baz","kane","benn","brendn","joyc"
$b="roh","dhaw","kohl"
$c="steyn","abd","faf","roh","dhaw"

Upvotes: 0

Views: 3088

Answers (3)

mjolinor
mjolinor

Reputation: 68341

A regex solution:

$a="dhaw","roh","kohl","faf","abd","steyn","gupt","baz","kane","benn","brendn","joyc"
$b="roh","dhaw","kohl"
$c="steyn","abd","faf","roh","dhaw"

$b_regex = ‘(?i)^(‘ + (($b |foreach {[regex]::escape($_)}) –join “|”) + ‘)$’
$c_regex = ‘(?i)^(‘ + (($c |foreach {[regex]::escape($_)}) –join “|”) + ‘)$’

Then, for elements of $a that aren't in $b:

$a -notmatch $b_regex 

faf
abd
steyn
gupt
baz
kane
benn
brendn
joyc

For elements of $a that aren't in $c:

$a -notmatch $c_regex

kohl
gupt
baz
kane
benn
brendn
joyc

And for elements of $a that aren't in $b or $c:

$a -notmatch $b_regex -notmatch $c_regex

gupt
baz
kane
benn
brendn
joyc

Runtime Regex

Note: this is just provided for demonstration for the people who left comments about it. This substantially faster than the -contains / -notcontains solutions, but for a single instance comparison it's probably overkill. It can produce substantial performance gains inside a loop where you're comparing one array to many other arrays.

Upvotes: 1

beatcracker
beatcracker

Reputation: 6930

Something like this?

Compare-Object -ReferenceObject $a -DifferenceObject ($b + $c)

If you just want to get raw objects:

(Compare-Object -ReferenceObject $a -DifferenceObject ($b + $c) |
    Where-Object {$_.SideIndicator -eq '<='}).InputObject

Upvotes: 1

Naigel
Naigel

Reputation: 9644

A viable solution could be using -notcontains operator as suggested by arco444, cycle through $a array elements and check if they are contained at least in one of the other arrays.

Here is a slice of code

foreach($a_value in $a) {
    if (($b -notcontains $a_value) -and ($c -notcontains $a_value)) {
        "$a_value is extra"
    }
}

Upvotes: 4

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