MediumCodingCoding10 min to answer

Given click counts by domain, aggregate counts for every parent subdomain.

Asked at

Palantir

1Give yourself 10 minutes

2Answer out loud, not in your head

3Then compare with the answer below

Stuck? Show a way to structure it+

01Clarify the objective, user, constraints, and acceptable failure modes.
02Structure the response around parsing, hash map, complexity, edge cases.
03Compare credible alternatives and state the decision criteria.
04Finish with validation, monitoring, and what would change the decision.

Reference answer

strong answer

I would first define the outcome and acceptable error boundary. I would explicitly cover parsing, hash map, complexity, edge cases. I would select an approach only after comparing quality, latency, cost, safety, and operational complexity, then validate it with representative cases and production monitoring.

parsing
hash map
complexity
edge cases

Must be adapted to the interviewer’s scenario
Would benefit from concrete numbers and personal examples

alternative answer

A second valid approach is to begin with the highest-risk assumption and test it cheaply. I would explicitly cover parsing, hash map, complexity, edge cases. I would select an approach only after comparing quality, latency, cost, safety, and operational complexity, then validate it with representative cases and production monitoring.

parsing
hash map
complexity
edge cases

Must be adapted to the interviewer’s scenario
Would benefit from concrete numbers and personal examples

Grade yourself

parsing

weight 30%

StrongExplains parsing concretely and ties it to a decision or measurable outcome.

WeakMentions parsing without implications, trade-offs, or evidence.

hash map

weight 25%

StrongExplains hash map concretely and ties it to a decision or measurable outcome.

WeakMentions hash map without implications, trade-offs, or evidence.

complexity

weight 25%

StrongExplains complexity concretely and ties it to a decision or measurable outcome.

WeakMentions complexity without implications, trade-offs, or evidence.

edge cases

weight 20%

StrongExplains edge cases concretely and ties it to a decision or measurable outcome.

WeakMentions edge cases without implications, trade-offs, or evidence.

Then expect these follow-ups

What are the time and space complexities?
Tests: depth
Which edge cases would you test?
Tests: adaptability
How would this work across multiple processes?
Tests: adaptability

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