How to Read a Coding Interview Problem (Without Burning 20 Minutes)
How to approach LeetCode and interview problems: a five-pass read that takes under four minutes, the questions to ask, and how to turn it into a spoken plan.
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Short answer: before writing code, make five quick passes over the problem. Restate it, pin down the input/output contract, name the brute force, guess the pattern, and set a complexity target. The whole read takes two to four minutes, and it saves you from rewriting half your solution when the interviewer asks "what about duplicates?"
Learning how to approach LeetCode problems in a real interview starts with treating "read the prompt" as active work, not skimming. Strong candidates use the first few minutes to pin down constraints and test cases before they commit to an algorithm. Weak candidates start typing and pay for it later.
These are the same phases a good interviewer probes for. See how to think out loud and what FAANG interviewers score.
The five-pass read (under four minutes)
Pass 1: restate it (30-45 seconds)
One or two sentences in your own words, no code. This catches misunderstandings while they are still cheap.
Pass 2: the input/output contract (about 45 seconds)
- Types and ranges, empty input, negative numbers, duplicates.
- What to return: indices or values, one answer or all of them?
- Can you modify the input?
Write two tiny examples you will trace later, including one awkward case (empty, all duplicates, a single element).
Pass 3: name the brute force (about 30 seconds)
Say the obvious O(n²) or exponential solution in one line. It gives you a correct baseline before you optimize, and interviewers like seeing it.
Pass 4: guess the pattern (about 60 seconds)
Tag it: two pointers, prefix sums, sliding window, graph traversal, binary search on the answer, and so on. If you are unsure, say so and test the guess: "This asks about a contiguous subarray, so sliding window is a candidate. Let me check it against my example."
Pass 5: set a complexity target (about 30 seconds)
Say what good enough looks like and why: "n can be 10^5, so O(n²) is about 10^10 operations, too slow. I'm aiming for O(n log n) or better." The time complexity guide shows how to reason from input size to target.
Red flags in problem statements
| Phrase or situation | Ask |
|---|---|
| "Sorted array" | Can there be duplicates? Can more than one answer be valid? |
| "Find any" vs "find all" | How large can the output get? |
| A graph | Directed? Acyclic? Possibly disconnected? |
| String matching | Case-sensitive? ASCII only or Unicode? |
| "In place" | Do you still need to return something? |
A polite question costs you seconds. Silently guessing wrong can cost you the round.
After the read: a spoken plan before you type
Spend 60 to 90 seconds on:
- The algorithm, and why it fits these constraints.
- Likely failure points (overflow, off-by-one, empty input).
- How you will test it, edge cases first.
This plan is the bridge between reading and coding under pressure. If you can't find a pattern in pass 4, the data structure decision guide gives you four questions that usually narrow it down.
A worked example: Two Sum
"Return two numbers in the array that add up to the target." Pass 2 is where this one turns. If the interviewer wants indices, you can't sort the array without tracking original positions, so a hash map from value to index is the natural fit. If they want the values and the array is already sorted, two pointers solve it in O(1) extra space. The same prompt leads to two different solutions depending on one clarifying question. The Two Sum guide walks through all three approaches, and you can try it on the Two Sum practice page.
FAQ
Is it OK to ask what complexity they want?
Yes, if you ask it collaboratively: "Is there a target complexity you'd like me to hit?" Some interviewers will tell you, which is a free hint.
What if I misread the problem?
Stop, say so plainly, and revise the plan. Interviewers give real credit for clean recovery. The stuck-in-an-interview playbook has wording that helps.
How do I practice reading?
Do ten timed reads a week with no code: just the five passes, out loud. Then run full mocks where you speak the passes before solving. TechInView's free practice set works for the reads, and the voice interview works for the full rehearsal.
Summary: approaching LeetCode problems in an interview is a repeatable read: restate, contract, brute force, pattern, complexity target. Then say your plan before you code.