Closest Pair of Points in 2D (Divide and Conquer)

Phone ScreenCitadelLast reported August 2026Low Frequency
Reported
2× across candidate reports
First seen
May 2025
Last reported
August 2026
Reported outcome
unknown

Problem Overview

You are given N points in a plane. Find the distance between the two closest points. Start with the straightforward answer, then optimise. In one report the candidate described brute force first, then divide and conquer; that interviewer required O(N log N). The other went straight to divide and conquer.…

  • 1 candidate-reported follow-up — the exact probes interviewers asked, with the trigger for each
  • The rest of the problem statement — full requirements, constraints, and edge cases
  • Approach and trade-offs — what passing candidates did, and the mistakes that sink people
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Verified Source
Every question is reconstructed from multiple independent candidate reports. Verbatim follow-ups, not invented ones.
Codex Fact-Checked
Technical claims, formulas, and scale numbers are reviewed against primary sources.
Interviewer Follow-ups
The exact follow-ups reported by candidates, with the trigger that prompts each one — plus the mistakes that sink people.
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