OA: Minimum Triggers to Absorb All Balls (Chain Attraction)

Also reported as Minimum Time to Collect All Plates

OAUberLast reported June 2026Medium Frequency

Reported: 5× across candidate reports
First seen: February 2026
Last reported: June 2026
Reported outcome: mixed

Problem Overview

Uber online assessment question, reconstructed from 5 candidate reports (February 2026 to June 2026). The write-up includes a Python solution that passes 8 test cases.

The full 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. Follow-ups candidates reported, not invented ones.

Codex Fact-Checked

Technical claims, formulas, and scale numbers are reviewed against primary sources.

Interviewer Follow-ups

The follow-ups candidates reported, with the trigger that prompts each one — plus the mistakes that sink people.