Topological Sort / Course Schedule

Problem Overview

You are given a list of courses (or services) with prerequisite/dependency relationships. The core task is to produce a valid topological ordering of the nodes. Two common variants observed: (1) Course Schedule variant — given course prerequisites as pairs, find the middle course in the dependency chain (part 1), then…

• 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