It's the job you really want. You are nervous, but have studied, prepped and researched. Then it happens – one of the interviewers asks you a hard question and you don’t know the answer. Should you try and fabricate a plausible response? Tell them politely that you just don’t know? How do you handle it? Here are some tips to help you break through and respond gracefully.
- Ask clarifying questions. Before assuming you don’t know the answer, make sure you understand the question. For example, make sure you clearly recognize the parameters and inputs of the problem. Sometimes learning more about the problem can help you understand it better.
- Work through some examples. Go through examples or alternative answers to the problem – such as something easy, like the base case. Then cite some more difficult, more complex ones . It’s By going through other answers, you’ll find it’s easier to identify patterns. .
- Break it down. After going through examples, it can help to identify assumptions and similarities in the problem. What are its different? Is there a way to solve part of it first and the rest of it second? You can also try questioning the parameters of the question. For example, if you had more data or less data could you solve the problem? Or perhaps relaxing one of the restrictions would you come up with a solution. Sometimes identifying some parts of the solution help you see another way of solving the whole thing.
- Solve it the obvious way first. Sometimes the easy, brute force solutions come to you quickly. Even if you know there may be a more elegant way to solve the problem, focus on getting one answer up first, then optimize it later. Too many candidates get hung up on the ideal and so can’t come up with any solution at all.
- Don't give up. Even if you can’t figure it out, don’t give up in exasperation. Keep trying and working through the problem. Your tenacity will impress the interviewer – since no employer wants to see you give up when you face something tough in the office. If you need to, start working through more examples – it can be a great way to get unstuck.
- Follow up after the interview. Even if you weren’t able to find an answer, follow up in an email with the best solution you can develop. Maybe even explain what you did wrong and how you improved used the experience to solve the problem. It shows that you are diligent and willing to follow through – even when the interview isn’t still on the line. Just make sure what you send in is correct and timely. Have someone check your work if necessary.
- Don't get discouraged. Everyone has bad interviews, so don’t let it get it you down or ruin the rest of your discussions. After all, the interviewer wouldn't be doing their job if they didn't ask you something you didn't know.
Always remember: Be gracious, keep working through it, and follow up afterward.
Kate Matsudaira has worked as the VP Engineering/CTO at several technology startups, including her current role at Decide and past roles at SEOmoz and Delve Networks. Before joining the startup world she was a software engineer and technical lead/manager at Amazon and Microsoft. She has hands-on knowledge and experience with building large scale distributed Web systems, Big Data, cloud computing and technical leadership -- and has conducted over 600 interviews in the last 5five years. She maintains a blog at http://katemats.com and also helps curate the Technical Leadership Newsletter http://www.techleadershipnews.com 
