Lowest Common Ancestor: BST First, Then Any Binary Tree

CodingMicrosoftLast reported February 2026Low Frequency

Reported: 2× across candidate reports
First seen: November 2025
Last reported: February 2026
Reported outcome: pass

Problem Overview

Microsoft coding question, reconstructed from 2 candidate reports (November 2025 to February 2026). Candidates reported 1 follow-up. The write-up includes a Python solution that passes 9 test cases.

1 candidate-reported follow-up — 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.