Technical Interviews: Whiteboarding
Clarifying the Problem

Whiteboarding interviews begin with a problem from the interviewer. The interviewee must be confident they understand the dimensions of the problem!

Software development is full of ambiguity. Programming requires concrete deliverables, but company needs can be murky. Even when the need is clear, a feature could have dozens of possible implementations. The ability to clearly define a problem is an important skill to demonstrate.

When the interviewer presents their technical question, repeat the question back to the interviewer in your own words. This gives you a moment to think and will resolve any glaring misunderstandings.

Once you’ve repeated the question, ask every clarifying question that comes to mind.

Assumptions must be communicated to the interviewer so there is agreement on the scope of the problem.

For example, if asked:

Write a function that returns duplicate characters in string.

Here are some questions which may come to mind:

  • What is the desired return value?
    • True|False, a list of characters, or …?
  • Do punctuation and spaces count as “characters”?
  • Should case be considered?
    • are "a" and "A" duplicates?
  • Should we be checking for Unicode characters?
  • Can we assume it’s a 26 character alphabet?


We’ll apply these steps to a single problem through the rest of the lesson.

Given a list of numbers, return whether the list contains Pythagorean Triplets.

Rephrase this problem in your own words and write that down.

Then, write down every question or assumption you have.

Watch the video to see how we clarified this question.

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