Game of Life: In-Place, Sparse and Infinite Board

Phone ScreenCitadelLast reported March 2026Low Frequency
Reported
1× across candidate reports
First seen
March 2026
Last reported
March 2026
Reported outcome
unknown

Problem Overview

The second of two Citadel Securities phone screens opened with LeetCode 289, Game of Life, and then kept raising the stakes. The problem below is the public LeetCode statement; the report adds the interviewer's requirements and follow-up questions. You are given a board of cells, each live (1) or dead…

  • 4 candidate-reported follow-ups — 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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