DSA mock interviews
Most DSA preparation is silent and solitary, which trains the wrong half of the skill. In the room you have to think out loud, and a correct solution explained badly still reads as luck.
Rounds with Sia from ₹49 · Live interviews with a working engineer from ₹500 · Pay per session
What a DSA round covers
Working the problem out loud
Restating the question, naming your assumptions, and choosing an approach before you write anything. This is the part studying alone never rehearses.
Complexity you can defend
Not just stating O(n log n), but saying where the cost comes from and what you would trade to move it. Expect to be asked for the space cost you skipped over.
Edge cases and correctness
Empty input, duplicates, overflow, and walking your own solution against a case you did not plan for. Finding your own bug scores better than being handed it.
The follow-up
Almost every question has a second half: make it faster, make it streaming, make it work when the input no longer fits in memory. Rehearsed answers come apart here.
DSA interview questions you might be asked
Not a list to memorise. Each is the kind of opening a real round uses, with what a strong answer covers — the follow-ups depend on what you say.
Find the first character that does not repeat in a string. Talk me through it before you write anything.
A first approach, its cost, then the improvement — counting in one pass and reading in a second — said out loud before any code.
Your solution is O(n²). Can you do better, and what does it cost you?
A faster approach and the memory it trades for speed. Naming that trade-off is worth as much as finding the faster solution.
Merge overlapping meeting times. What inputs would break your first version?
Empty input, a single meeting, meetings that only touch, and unsorted input — found by you, by walking through your own code.
When would you pick a heap over sorting the whole list?
When you only need the top k, or the data keeps arriving — with the complexity of each option compared directly.
Now the input is too large to fit in memory. What changes?
The usual second half of a DSA question: streaming, chunking or an approximate answer, and what each one gives up.
Answer questions like these in a scored round and see exactly where your answer fell short.
What the interviewer is listening for
Interviewers score the path more than the destination. A candidate who narrates a wrong first approach, spots why it fails and adjusts usually outscores one who produces the optimal answer in silence.
Where candidates lose marks
- Writing code before stating the approach.
- Going quiet for minutes at a time while thinking.
- Reciting a memorised solution and stalling on the follow-up.
Two ways to interview
A round with Sia, on your own
One question at a time with real follow-ups on what you actually said. Choose three, five or eight questions. Scored the moment you finish, with a written breakdown across technical depth, problem solving and communication.
A live interview with an engineer
Forty minutes over Zoom with someone who runs DSA interviews for a living. They score five criteria and write up what to fix, and you keep a numbered certificate for the session.
Pick your stack for a round with Sia: Data structures · Java · Python · C++ · C · JavaScript.
Questions about DSA interviews
Which language should I use for a DSA round?
Whichever you will use in the real interview. Java, Python, C++, C and JavaScript are all available for a round with Sia.
Is a DSA round right for a fresher?
It is the round freshers meet most often, especially in campus placements. Beginner difficulty keeps to the core data structures before moving to harder problems.
Do I have to reach the optimal solution to score well?
No. The way you get there counts: stating your approach, spotting why a first idea fails and fixing it out loud often scores better than a silent perfect answer.
How is a DSA round scored?
On the same five criteria as every round — technical depth, problem solving, communication, behavioural and code quality. In a DSA round, how you explain your approach shows up in problem solving and communication, not just in whether the code works.
Read before your round
DSA interviews by technology
Other tracks
Not sure which to book? The FAQ covers how sessions are scored, and candidate stories show what people did with the feedback.