The table data are stored as a simple treeview:
LineNumber : Simply the number of the line
Level : depth of the treeview
ID : Id of the Child

The table doesn't have the parent id.

I need to determine the child ID by using the depth the relation parent-child.
In my exemple :
My root id is 10
First child level id of 10 are 11, 20 and 30
Childs of 11 are 13, 14 and child of 14 is 15.

for example, I receive an ID for the where clause : 30
I want to get the build this result :

ParentID ChildID Path
30 31 30 31
31 33 30 31 33
30 32 30 32
30 34 30 34
34 35 30 34 35
35 36 30 34 35 36

Usually, we start from table with ParentID, ChildID and with "connect by" hierarchical query we obtain as reslult my starting table.

My need is like I want to reverse the process from result to data.

with rws as (
  select 1 LineNumber, 1 mylevel, 10 id from dual
  union all
  select 2 , 2 , 11 from dual
  union all
  select 3 , 3 , 13 from dual
  union all
  select 4 , 3 , 14 from dual
  union all
  select 5 , 4 , 15 from dual
  union all
  select 6 , 2 , 20 from dual
  union all
  select 7 , 2 , 30 from dual
  union all
  select 8 , 3 , 31 from dual
  union all
  select 9 , 4 , 33 from dual
  union all
  select 10 , 3 , 32 from dual
  union all
  select 11 , 3 , 34 from dual
  union all
  select 12 , 4 , 35 from dual
  union all
  select 13 , 5 , 36 from dual
)
  select prior id par_id, id, level, sys_connect_by_path( id, '/')
  from   rws
  start with id = 30
  connect by mylevel = prior mylevel + 1
  and prior id < id;
  
PAR_ID    ID    LEVEL    SYS_CONNECT_BY_PATH(ID,'/')   
   <null>    30        1 /30                            
       30    31        2 /30/31                         
       31    33        3 /30/31/33                      
       33    36        4 /30/31/33/36                   
       31    35        3 /30/31/35                      
       35    36        4 /30/31/35/36                   
       30    32        2 /30/32                         
       32    33        3 /30/32/33                      
       33    36        4 /30/32/33/36                   
       32    35        3 /30/32/35                      
       35    36        4 /30/32/35/36                   
       30    34        2 /30/34                         
       34    35        3 /30/34/35                      
       35    36        4 /30/34/35/36

Given that the data is stated to be a "treeview" and in the followup review that it needs to be "reverse engineered", we can make some assumptions.

If we assume that the data we have are the output of a connect by query like this:

select
   rownum as linenumber
 , level as mylevel
 , id
from source_data
start with parent_id is null
connect by parent_id = prior id
order siblings by id;

Then we can assume that a parent is the last row before the current row that has a smaller level.

That enables us to find the parent id for example like this:

with rws as (
  select 1 LineNumber, 1 mylevel, 10 id from dual
  union all
  select 2 , 2 , 11 from dual
  union all
  select 3 , 3 , 13 from dual
  union all
  select 4 , 3 , 14 from dual
  union all
  select 5 , 4 , 15 from dual
  union all
  select 6 , 2 , 20 from dual
  union all
  select 7 , 2 , 30 from dual
  union all
  select 8 , 3 , 31 from dual
  union all
  select 9 , 4 , 33 from dual
  union all
  select 10 , 3 , 32 from dual
  union all
  select 11 , 3 , 34 from dual
  union all
  select 12 , 4 , 35 from dual
  union all
  select 13 , 5 , 36 from dual
)
select
   rws.id
 , (
      select max(id) keep (dense_rank last order by linenumber)
      from rws prev_parents
      where prev_parents.linenumber < rws.linenumber
      and prev_parents.mylevel < rws.mylevel
   ) as parent_id
from rws;

(I tried if I could do it with LAST_VALUE IGNORE NULLS, but couldn't. MATCH_RECOGNIZE isn't available on 11g. MODEL clause perhaps, but I couldn't think of way without spending a lot of time on it. The scalar subquery works, but if it's a large dataset, it'll probably not be fast.)

We can check if the reverse engineering was correct:

with rws as (
  select 1 LineNumber, 1 mylevel, 10 id from dual
  union all
  select 2 , 2 , 11 from dual
  union all
  select 3 , 3 , 13 from dual
  union all
  select 4 , 3 , 14 from dual
  union all
  select 5 , 4 , 15 from dual
  union all
  select 6 , 2 , 20 from dual
  union all
  select 7 , 2 , 30 from dual
  union all
  select 8 , 3 , 31 from dual
  union all
  select 9 , 4 , 33 from dual
  union all
  select 10 , 3 , 32 from dual
  union all
  select 11 , 3 , 34 from dual
  union all
  select 12 , 4 , 35 from dual
  union all
  select 13 , 5 , 36 from dual
),
source_data as (
   -- reverse engineered
   select
      rws.id
    , (
         select max(id) keep (dense_rank last order by linenumber)
         from rws prev_parents
         where prev_parents.linenumber < rws.linenumber
         and prev_parents.mylevel < rws.mylevel
      ) as parent_id
   from rws
)
select
   rownum as linenumber
 , level as mylevel
 , id
from source_data
start with parent_id is null
connect by parent_id = prior id
order siblings by id;

Looks to me like it gives the same output ;-)

with rws as (
  select 1 LineNumber, 1 mylevel, 10 id from dual
  union all
  select 2 , 2 , 11 from dual
  union all
  select 3 , 3 , 13 from dual
  union all
  select 4 , 3 , 14 from dual
  union all
  select 5 , 4 , 15 from dual
  union all
  select 6 , 2 , 20 from dual
  union all
  select 7 , 2 , 30 from dual
  union all
  select 8 , 3 , 31 from dual
  union all
  select 9 , 4 , 33 from dual
  union all
  select 10 , 3 , 32 from dual
  union all
  select 11 , 3 , 34 from dual
  union all
  select 12 , 4 , 35 from dual
  union all
  select 13 , 5 , 36 from dual
)
select
   rws.id
 , (
      select max(id) keep (dense_rank last order by linenumber)
      from rws prev_parents
      where prev_parents.linenumber < rws.linenumber
      and prev_parents.mylevel < rws.mylevel
   ) as parent_id
from rws;

        ID  PARENT_ID
---------- ----------
        10
        11         10
        13         11
        14         11
        15         14
        20         10
        30         10
        31         30
        33         31
        32         30
        34         30
        35         34
        36         35

13 rows selected.

with rws as (
  select 1 LineNumber, 1 mylevel, 10 id from dual
  union all
  select 2 , 2 , 11 from dual
  union all
  select 3 , 3 , 13 from dual
  union all
  select 4 , 3 , 14 from dual
  union all
  select 5 , 4 , 15 from dual
  union all
  select 6 , 2 , 20 from dual
  union all
  select 7 , 2 , 30 from dual
  union all
  select 8 , 3 , 31 from dual
  union all
  select 9 , 4 , 33 from dual
  union all
  select 10 , 3 , 32 from dual
  union all
  select 11 , 3 , 34 from dual
  union all
  select 12 , 4 , 35 from dual
  union all
  select 13 , 5 , 36 from dual
),
source_data as (
   -- reverse engineered
   select
      rws.id
    , (
         select max(id) keep (dense_rank last order by linenumber)
         from rws prev_parents
         where prev_parents.linenumber < rws.linenumber
         and prev_parents.mylevel < rws.mylevel
      ) as parent_id
   from rws
)
select
   rownum as linenumber
 , level as mylevel
 , id
from source_data
start with parent_id is null
connect by parent_id = prior id
order siblings by id;

LINENUMBER    MYLEVEL         ID
---------- ---------- ----------
         1          1         10
         2          2         11
         3          3         13
         4          3         14
         5          4         15
         6          2         20
         7          2         30
         8          3         31
         9          4         33
        10          3         32
        11          3         34
        12          4         35
        13          5         36