Performing in a Coding Interview
Explore techniques to excel in coding interviews by developing a structured approach to problem-solving. Learn how to clarify constraints, think aloud to communicate reasoning, select optimal data structures, handle feedback, and verify your solution to improve your interview performance.
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Knowing data structures is necessary but not sufficient. Interviewers evaluate how we think, not just whether we arrive at the correct answer. A candidate who produces a correct solution in silence, without explaining their reasoning, will consistently underperform compared to a candidate who communicates clearly, even if their final code is less optimal.
The first five minutes
The first five minutes of a coding interview are the most important. This is where we demonstrate problem-solving instincts before writing a single line of JavaScript. Candidates who jump straight into coding almost always make avoidable mistakes: they solve the wrong version of the problem, miss an edge case that changes the approach, or choose a data structure that works but is not optimal.
The first five minutes should follow a consistent structure every time:
Read the problem completely: Do not start thinking about solutions until we have read the entire problem statement. Key constraints often appear at the end.
Clarify constraints out loud: Ask about input size, whether the input is sorted, whether duplicates are possible, and what the expected output format is. These questions signal thoroughness and often reveal constraints that change the solution entirely.
Work through a small example by hand: Before touching code, trace through a concrete example. This builds intuition, confirms our understanding of the problem, and often reveals the pattern we need.
State the approach and complexity before coding: Say out loud which data structure we will use, ...