Serialize and Deserialize a Binary Tree, Then an N-ary Tree

Phone ScreenUberLast reported October 2026Low Frequency
Reported
2× across candidate reports
First seen
June 2026
Last reported
October 2026
Reported outcome
unknown

Problem Overview

Uber phone-screen question, reconstructed from 2 candidate reports (June 2026 to October 2026). Candidates reported 2 follow-ups. The write-up includes a Python solution that passes 9 test cases.

  • 2 candidate-reported follow-ups — the probes candidates report being asked, with the trigger for each
  • 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.
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