Practise the coding round the way it is run: one problem, a clock, and a solution that has to pass real test cases. Solve in Java, Python or C++ - free, with no credit card.
A DSA mock interview is a practice run of the coding round - the part of a software engineering interview where you solve a data structures and algorithms problem in 45 to 60 minutes while an interviewer watches how you think. Product companies, from FAANG to Indian unicorns, use it to screen almost every SDE-1 and SDE-2 candidate.
Solving problems at your own pace is not the same skill. In the real round you have a clock, no hints from a discussion tab, and someone waiting for you to explain your complexity. A mock interview recreates that pressure so the first time you feel it is not the day that counts.
On InstaMock you get the mechanics of the round for free: pick a problem, write your solution in the editor, run it on sample tests as you go, then submit against the full test suite. Passed cases, execution time and your submission history are kept per problem, so you can come back and beat your own solution.
The structure most coding rounds follow. Hold yourself to these timings and say each step out loud.
Restate the problem, ask about input size, duplicates, negatives and empty input. Write two examples of your own.
Say the simplest correct approach and its complexity out loud before improving it. It proves you understood the problem.
Find the pattern - hashing, two pointers, sliding window, BFS, DP - and state the new time and space complexity.
Write clean code with readable names. Talk through the tricky lines rather than going silent.
Dry-run an example, then the edge cases. Run against the test cases and fix what fails.
Re-check complexity, discuss trade-offs, and say what you would change with more time.
A correct answer is necessary but not sufficient. Interviewers grade five things.
Did you clarify constraints and edge cases before writing code, or start typing on a guess?
Can you move from a brute force to an optimal approach and state the Big-O of both correctly?
Does the solution pass the full set of test cases, including the empty, single-element and large inputs?
Readable names, no dead code, small helper functions where they help - code a teammate could review.
Interviewers score your reasoning as much as your answer. Thinking aloud turns a stuck moment into a hint.
35 topics in the order interviews build on them. Each topic has a tutorial and its own problem set.
Good first problems for a timed mock round - each one tests a pattern that recurs across companies.
₹0 · no credit card
₹499 for 60 minutes · ₹899 for two
Yes. Every DSA problem on InstaMock is free to solve - all 670 of them, with no credit card and no trial period. A live 1:1 DSA round with an engineer is the only paid option, at ₹499 for a 60-minute interview.
You pick a problem, write your solution in the in-browser editor, run it against sample test cases while you work, and submit it against the full test suite. You see which cases passed, the execution time, and your past submissions for that problem.
Java, Python and C++. You can switch language per problem, and each one starts from a ready-made function template.
670 problems: 212 Easy, 257 Medium and 201 Hard, grouped into 35 topics from arrays and hashing through graphs and advanced dynamic programming.
Give yourself 45 minutes per problem - the length of most real coding rounds. Spend roughly 10 minutes understanding and planning, 15 coding, and the rest testing and reviewing. Practising under the clock is what makes the real round feel familiar.
Five things: whether you clarified the problem, whether you reached an optimal approach and know its complexity, whether your code works on edge cases, whether it is readable, and whether you explained your thinking while you worked.
Arrays and hashing, two pointers, sliding window, binary search, trees, graphs (BFS, DFS, shortest path) and dynamic programming cover the large majority of coding rounds at product companies. Start there, then add heaps, tries and union-find.
Yes. Book a 60-minute 1:1 mock interview for ₹499, or two for ₹899. A working engineer runs a live coding round, asks follow-up questions, and sends written feedback afterwards.
Pick a problem, start the clock, and submit against real test cases.
Start a Free DSA Mock Interview