Implement Vending Machine (OO Design)

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

Problem Overview

Design and implement a vending machine system. The problem has 3 parts and starter code is provided. The system must handle: (1) inserting bills/currency, (2) making change, and (3) additional vending machine functionality as revealed in subsequent parts.…

  • 3 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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