Powershell how to know if a list's elements are numbered consecutively

Question

I´m trying to know if all the PC are in the list and if one it´s not on the list the script will say me, the list can be modificate with more PC.

$equipos= "equipo1","equipo2","equipo3","equipo5"
[char]$nequipos = 1

for($i=0;$i -lt $equipos.count;$i++){
    [char]$num = $equipos[$i][6]
    if($num -ne $nequipos){
    write-host "equipo"$nequipos
    }
[char]$nequipos= $i++
}

Answer 1

The following finds the gaps in the numbering and lists all available names based on the missing numbers:

# Extract all numbers contained in the names.
[int[]] $numbers =  "equipo1", "equipo2", "equipo3", "equipo5" -replace '\D'
# Find the highest number.
$highestNumber = [Linq.Enumerable]::Max($numbers)

# Find all unused numbers.
$unusedNumbers = Compare-Object $numbers (1..$highestNumber) -PassThru

# Report results.
if ($unusedNumbers) {
  Write-Verbose -Verbose "The following names are available: "
  $unusedNumbers.ForEach({ 'equipo' + $_ })
} else {
  Write-Verbose -Verbose "No gaps in numbering found."
}

Output:

VERBOSE: The following names are available:
equipo4

Note:

• -replace '\D' removes all non-digit (\D) characters from the names and casts the resulting strings to [int[]] in order to get an array of numbers.

• [Linq.Enumerable]::Max($numbers) finds the maximum (highest number) among them. See the .NET docs.

• Compare-Object is used to compare the extracted numbers to the (gap-less) range (..) of numbers from 1 to the highest one (1..$highestNumber). By default, the elements that are different between the input collections are reported and, thanks to -PassThru, those extracted numbers that are missing from the range are directly output.

• $unusedNumbers.ForEach({ 'equipo' + $_ }) uses the .ForEach() array method to construct the list of names for the unused numbers in the range.

Answer 2

Assuming the names are unique, you can pick the highest number in the sequence and subtract the length of the list - that'll give you the number of gaps:

$equipos = "equipo1","equipo2","equipo3","equipo5" |Sort-Object {$_ -replace '^\D+' -as [int]} -Unique -Descending 

$highest = $equipos |Select -First 1
$number = $highest -replace '^\D+' -as [int]
if($number -gt $equipos.Length){
  "There are $($number - $equipos.Length) gap(s) in the list"
} 
else {
  "The list is contiguous"
}

Which, with the given sample values, will output:

There are 1 gap(s) in the list