function Group-Numbers {
<#
.SYNOPSIS
    Group an array of numbers into islands of contiguous sequences
#>
    [CmdletBinding()]
    [OutputType([System.Collections.ArrayList])]
    param (
        [Parameter(Mandatory = $true)]
        [int[]]$Values
    )

    $groups = (New-Object -TypeName "System.Collections.ArrayList")

    if ($Values.Length -eq 0) {
        return $groups
    }

    $len = $Values.Length
    $group = (New-Object -TypeName "System.Collections.ArrayList")
    $group.Add($Values[0]) | Out-Null
    for($i = 1; $i -lt $len; $i++) {
        if (($Values[$i] - $Values[$i-1]) -eq 1) {
            $group.Add($Values[$i]) | Out-Null
        } else {
            $groups.Add($group) | Out-Null
            $group = (New-Object -TypeName "System.Collections.ArrayList")
            $group.Add($Values[$i]) | Out-Null
        }
    }
    $groups.Add($group) | Out-Null

    return $groups
}