Given a list of paths, remove all paths whose parent is already in the list.

Get-PathCollapsed.ps1

<#
.SYNOPSIS
Given a list of paths, remove all paths whose parent is already in the list.
#>
function Get-PathCollapsed
{
    param (
        [string[]] $Paths
    )

    [System.Collections.ArrayList] $collapsedPaths = @()

    $Paths | % { $p = $_
        if ($collapsedPaths.Count -eq 0)
        {
            $collapsedPaths += $_
        }
        else
        {
            $isParent = $true
            $itemToSwap = $null
            $collapsedPaths | % {
                if ($p -like "$_*")
                {
                    $isParent = $false
                }
                elseif ($_ -like "$p*")
                {
                    $itemToSwap = $_
                }
            }

            if ($isParent)
            {
                $collapsedPaths += $p
            }

            if ($itemToSwap)
            {
                $collapsedPaths.Remove($itemToSwap)
            }
        }
    }

    return $collapsedPaths
}