The Coding Interview
A complete overview of the live coding interview format used at top tech companies.
Definition
A coding interview is a live, time-boxed (typically 45-minute) session where a candidate solves one or two algorithmic problems in front of an interviewer using a shared editor, whiteboard, or collaborative IDE. The format tests not only the correctness of the final solution but also the candidate's problem decomposition, communication, and ability to reason about edge cases and complexity under time pressure. Coding interviews are the gating round for software engineering roles at virtually every top tech company.
Why It Matters in Interviews
According to a widely cited Tech Interview Handbook review of FAANG hiring, coding interviews account for roughly 60% of the engineering hiring decision at junior and mid levels, and remain a required round even at senior. A weak coding round is the single most common reason candidates are rejected, and unlike behavioral rounds, it is rarely overcome by strength elsewhere in the loop.
How to Use It
Use a four-step framework on every problem: (1) restate the problem and ask 2 to 3 clarifying questions, (2) walk through 2 examples including an edge case, (3) outline your approach and complexity before coding, (4) write code while narrating, then test mentally on the examples. Never start coding silently. Related reading: LeetCode Patterns and System Design Basics.
Example
"Before I code, let me clarify: the array can contain negatives, right? And can the same element be used twice? OK. My approach is a hash map for O(n) time and O(n) space — I'll iterate once and check the complement. Let me code it… [writes solution] … now let me trace through [3, 2, 4], target 6 — first iteration map is empty, second we store 3, third 4 looks up 6-4=2 which is in the map, so we return [1,3]. Looks right."
Quick Tips
- Talk continuously — silent coding is the most common reason for "weak signal" debrief notes.
- State the time and space complexity before you write any code.
- Test your code on at least one edge case (empty input, single element, duplicates) before saying you're done.
- If stuck, propose a brute-force solution first then optimize — partial credit is real.
FAQ
How many problems will I solve?
Usually one medium problem with deep follow-ups, or two easier problems back-to-back. The interviewer is testing depth, not speed.
Can I use my preferred language?
Yes, at almost every company. Pick the language you are fastest in — interviewers care about clarity, not language choice.
What happens if I don't finish the problem?
You can still pass. A clear approach with strong communication often scores higher than a finished but messy solution.