I applied in D.E. Shaw through referral in february 2022

Coding round:-
The coding round was on HackerRank and it included 3 sections , each section had one question and there was a time limit for each section (switching between the sections was not allowed ) .
the first section was of 20 min time and it included problem which was highly focused upon implementation.
The second section was of 30 mins and this was hard problem of binary search and the 3rd section was also of 30 mins and this problem was a tricky one and belonged to two-pointers.
I submitted 2 questions fully and 3rd question partially.
after 3-4 days, I received mail regarding the interview.

1st Technical Round:-
in this Round , i was given a code-pair link of hackerrank and i was given with an easy problem (greedy ). I wrote the code within 2 minutes and explained the approach of it within 10-15 mins.
We had discussion of Operating System for the next 40-45 mins.
topics:-

1. Inter-Process communcation
2. Semaphores
3. locks
4. Mutex
   then a small discussion of 10 mins over OOPS
5. Virtual functions
6. Polymorphism

I gave answers to all the questions asked by the interviewer and i was pretty sure of qualifying this round.
after 1 day, I received the call regarding qualifying for next round.

2nd Technical Round (in-House interview Round):-

This was very difficult Round for me and it didn't went well
this round had 2 coding questions

1. Given a number N in string format find the number just smaller than N such that it has digit x present in it x times. example:- given number:- 234235 answer:- 224444
2. Given 2 strings S1 and S2 . Find largest string S3 such that S1 and S2 both are concatenation of S3 string
   example:- S1: abaaba S2: abaabaaba then S3 :- aba

I solved 2nd question fully but faced difficulty in solving the 1st one and solved it partially.
Next we had dicussion over 10-15 minutes over Operating System
Topics:-

1. Paging
2. Segmentation

I qualified this Round but wasn't expecting because of messing up in 1st question
they notified me the very next day

3rd Technical Round (last round):-
In this round they gave me a problem which i already solved in a codechef contest and was of multisource BFS.
it took me 20 mins to explain and wrote code within 7-10 mins.
they asked a lot of questions regarding time complexity and space complexity
then they started with CS fundamentals for the next 55-60 minutes, this time they took it in real depth and asked concepts deeply

1. diamond problem (with ouput questions) i gave the definition but messsed up in output question
2. virtual in OOPS
3. Inter-process communication
4. shared-memory
5. process thread (in depth , messed up here too)
6. Locking in OS (with code)
7. TCP vs. UDP
8. Checksum (I told them not to ask much questions from computer network)
9. IP addressing

so this round wasn't that good but went well as i answered most of the questions. but had negative impact because of (in-depth questions)

this Round was on 9th April
and I still didn't received any mail or call from D.E Shaw regarding acceptance or rejection
I even called the HR they told me to wait for 1- 2 weeks for any update and here i am
if anyone of you got please mention in comments
Thankyou