Clarifying Questions in English for Coding Interviews

A clarifying question is a question you ask to check you understand a task before you answer it, for example “Can I assume the input is sorted?”. In interviews, restate the problem, then ask about constraints, edge cases and output format in the first two minutes, before you write code.

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In a live technical interview, jumping straight into a solution after the interviewer asks a question is not the right move. Taking time to ask clarifying questions first shows the interviewer that you think carefully and fully understand a problem before you start solving it.

What to clarify

Technical interview questions are often left vague on purpose. The interviewer wants to see if you can identify what is missing and ask the right questions.

Assumption. Something you accept as true without being told directly. Always state your assumptions clearly.
Constraint. A rule or limit on your solution. For example: memory limits, time limits, or allowed tools.
Edge case. An unusual or extreme input that could break your solution. For example: an empty list, a very large number, or a null value.
Use case. A real-world example of how something is used. Helps you understand what the solution needs to do.
Scale. How large the problem is. For example: how many users, how much data, how many requests per second.

The structure

Clarification checklist

Restate the problem — Repeat the problem in your own words to confirm you understood it.
Ask clarifying questions — Ask about anything that is unclear - scale, input format, expected output.
Confirm assumptions — State what you are assuming and ask if that is correct.
Consider edge cases — Mention unusual situations that your solution might need to handle.
Outline your process — Before you start, briefly describe your approach.

Model answer

Restate. "OK, so you would like me to check whether a given string reads the same forwards and backwards - is that correct?"
Clarify. "Should I ignore spaces and punctuation in the string?"
Interviewer. "Yes, you can ignore all non-alphanumeric characters and case."
Edge case. "We should also think about edge cases - for example, an empty string. Is it possible to receive an empty input?"
Constraint. "Would you prefer that I do the reversal manually, or can I use built-in functions?"
Process. "OK. I am going to explain my approach at a high level first, and then I will start writing the code."

15 clarifying questions you can copy

Inputs and outputs

"Just to confirm - what is the expected input format?"
"What should I return if the input is empty or null?"
"Should the output be sorted, or is any order fine?"
"Are duplicate values allowed in the input?"

Constraints and scale

"What is the expected size of n - hundreds, millions?"
"Are there memory or time constraints I should optimise for?"
"Can I assume the input fits in memory?"
"Is this a single-machine problem, or should I think about distributed scale?"

Edge cases

"Should I handle negative numbers / empty strings / Unicode?"
"What happens if two users update the same record at once?"
"Is the graph guaranteed to be connected / acyclic?"

Approach check

"Would you like a brute-force first, then an optimised version?"
"Is it OK if I state my assumptions and then start coding?"
"Do you want production-ready code, or is a clear algorithm enough?"
"Should I talk through complexity before I write the solution?"

Common mistakes

Not confirming assumptions — If the interviewer does not give details, state your assumption clearly and explain why. "Since the values represent a number of people, I will assume inputs cannot be negative."
Asking vague questions — Do not ask "How should I start?" Instead be specific: "Would you prefer I start with the simple solution or the more efficient one?"
Asking too many questions at once — Ask one question at a time and wait for the answer before asking the next one.

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FAQ

Questions

A question that checks you have understood a request before you act on it. It confirms a detail you were given (“So the list can contain duplicates?”) or asks for one you were not (“What should I return if the input is empty?”). It is not a request to repeat the question.

“Just to confirm, what is the expected input format?”, “Can I assume the input fits in memory?”, “Should the output be sorted?”, “Would you like a brute-force solution first?” and, outside coding rounds, “Do you mean a project I led, or one I contributed to?”

Restate the problem, then ask about input constraints, edge cases, and output format. Do this in the first two minutes, before you write code.

Three or four targeted questions beat ten vague ones. If the interviewer already answered, repeat the constraint and start the approach.

More questions? Email us at contact@mocklyenglish.com.

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