SQL: Find missing folders paths in splitting hierarchies - Recursive, Sql Server

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create table t (DirID int, BaseDirID int, DirLevel int, DisplayPath varchar(64))
insert into t values 
 (1,1,1,'A')
,(2,1,3,'A\B\C')
,(3,1,5,'A\B\C\D\E')
,(4,1,3,'A\B\F')
,(5,1,5,'A\B\F\G\H')
,(6,2,1,'U')
,(7,2,3,'U\V\W')
,(8,2,5,'U\V\W\X\Y')
,(9,2,3,'U\V\M')
,(10,2,5,'U\V\M\L\O')
,(11,2,9,'U\V\Z\L\O\Q\R\S\T');
create clustered index cix_tbl_DirId on dbo.t(DirID);

with cte as (
select BaseDirID, DisplayPath = left(DisplayPath,len(DisplayPath)-charindex('\',reverse(DisplayPath)))
from t
where DirLevel > 1
  and not exists (
  select 1 
  from t i
  where t.BaseDirId = i.BaseDirId
    and i.DisplayPath = left(t.DisplayPath,len(t.DisplayPath)-charindex('\',reverse(t.DisplayPath)))
    )
union all 
select BaseDirID, DisplayPath = left(DisplayPath,len(DisplayPath)-charindex('\',reverse(DisplayPath)))
from cte t
where not exists (
  select 1 
  from t i
  where t.BaseDirId = i.BaseDirId
    and i.DisplayPath = left(t.DisplayPath,len(t.DisplayPath)-charindex('\',reverse(t.DisplayPath)))                                                   
    )
)
select distinct * 
from cte

View schema
Execution time: 0,03 sec, rows selected: 12, rows affected: 11, absolute service time: 0,2 sec