SQL> set autotrace on statistics
SQL> set timing on
<again, third run>
SQL> select object_name, object_type
  2    from ( select o.*, max(last_ddl_time) over ( partition by owner ) last_modified_time
  3             from all_my_objects o
  4         )
  5   where last_ddl_time = last_modified_time;

OBJECT_NAME                    OBJECT_TYPE                                      
------------------------------ -------------------                              
<output snipped>

528 rows selected.

Elapsed: 00:00:13.04

Statistics
----------------------------------------------------------                      
          0  recursive calls                                                    
          0  db block gets                                                      
      11002  consistent gets                                                    
       6025  physical reads                                                     
          0  redo size                                                          
      15497  bytes sent via SQL*Net to client                                   
        805  bytes received via SQL*Net from client                             
         37  SQL*Net roundtrips to/from client                                  
          1  sorts (memory)                                                     
          0  sorts (disk)                                                       
        528  rows processed