LeetCode Card 303 — Topological Sort / Structure
Pattern signal
This pattern usually appears when the prompt involves ordering with prerequisites in a DAG. Course Schedule, build order, dependency resolution, and task execution pipelines point here.
What Structure means here
In BASIC, the Structure step is where you state the invariant, helper contract, or control-flow skeleton before coding. For Topological Sort, that matters because the pattern only becomes useful once the candidate is explicit about what is being tracked, reduced, or preserved.
Interview move
A strong move is to make the plan visible before full execution. In this pattern family, say out loud what representation makes the problem easier: the map entry, the pointer invariant, the recursion contract, the queue contents, or the DP state. That keeps the implementation attached to a reason.
Common miss
Candidates detect dependencies but fail to distinguish cycle detection from valid ordering construction. BASIC reduces that risk because the stage sequence forces you to earn the implementation instead of jumping straight into it.
BASIC prompt
“Given that this looks like Topological Sort, what is the simplest way to state the invariant, helper contract, or control-flow skeleton before coding?”