Finding n matching files by sub-path recursively inside a directory - powershell

Question

I have a file structure like:
RootDir\
ADir
1.xml
2.xml
BDir
1.xml
2.xml
3.xml
CDir
2.xml
3.xml
I need to write script to recursively check if a file exists in more than one directory under RootDir, where the file path is identical from one level below RootDir.
For example RootDir\ADir\1.xml also exists in location RootDir\BDir\1.xml
The code below returns the path of matching entries, however it also continues to match with iteself, despite the -exclude switch
$rootCompare = "C:\Users\XXX\Documents\Compare\RootDir"
$rootItems = get-childitem -Path C:\Users\XXX\Documents\Compare\RootDir -Recurse
foreach ($i in $rootItems){
$dirItems = get-childitem $i -File -Recurse | ForEach-Object {
$fullName = $_.fullName
$baseName = $_.baseName
$baseExt = $_.Extension
Write-Host "fullname="$fullName
if (Test-Path $rootCompare\*\$baseName$baseExt -Exclude $fullName) {
$fileSearch = get-ChildItem -Path $rootCompare\*\$baseName$baseExt -Exclude "*$fullName*"
Write-Host "searching for file: "$fullName
Write-Host "file exists in another location: "$fileSearch
}
}
}
Example return:
fullname= C:\Users\XXX\Documents\Compare\RootDir\CDir\3.xml
searching for file: C:\Users\XXX\Documents\Compare\RootDir\CDir\3.xml
file exists in another location: C:\Users\XXX\Documents\Compare\RootDir\ADir\3.xml
C:\Users\XXX\Documents\Compare\RootDir\CDir\3.xml
1) How can I adapt the exclude condition to prevent it from matching with itself?
2) This version only works at 1 level below RootDir. How should it be adapted to work n levels below RootDir?
For example RootDir\ADir\DDir\1.xml should also match RootDir\BDir\DDir\1.xml but not RootDir\ADir\1.xml
Important point:
The number, name and paths the of directories are dynamic and cannot be hard-coded

Answer 1

The quick and dirty way of how I would do it is to do a single Get-ChildItem -Recurse into a variable. Then I could iterate through that variable twice. Once to get the first list of objects, and a second to compare to the first. Then in the comparison we want to match where the Name is the same, and the FullName doesn't match.
$rootCompare = "C:\Users\XXX\Documents\Compare\RootDir"
$rootItems = get-childitem -Path $rootCompare -Recurse
foreach ($i in $rootItems){
foreach ($j in $rootItems){
if($i.Name -eq $j.Name -and $i.fullName -ne $j.fullName)
{
Write-Host "file" $i.fullName
Write-Host "also exists in another location: "$j.fullName
}
}
}