Happy Number (LC 202)

CodingSnowflakeLast reported June 2026Low Frequency
Reported
2× across candidate reports
First seen
May 2025
Last reported
June 2026
Reported outcome
unknown

Problem Overview

Given a positive integer n, determine whether it is a 'happy number'. A happy number is defined by the following process: starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number either equals 1 (where it…

  • 2 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
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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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