Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

$WebURL="http://sharepoint.DOMAIN.com"
$LibraryURL="/General%20Documents" #Relative URL

$Web = Get-SPWeb $WebURL
$Folder = $web.GetFolder($LibraryURL)

Function CheckIn-CheckedOutFiles($Folder){
    $Folder.Files | Where { $_.CheckOutStatus -ne "None" }  | ForEach-Object {
        write-host ($_.Name,$_.URL,$_.CheckedOutBy)
        #To Check in
        #$_.Checkin("Checked in by Administrator")
    }
    $Folder.SubFolders | ForEach-Object {
        CheckIn-CheckedOutFiles $_
    }
}

CheckIn-CheckedOutFiles $Folder