A graph-boundary self-check tests mutual reachability, all-pairs costs, cycle rejection and component interpretation.
Review the contracts
Review strong components, all-pairs paths, reachability checks before answering.
Choose and explain an answer
Distinguish one-way reachability from a shared strong component. Separate an absent edge from a finite cost before reasoning about path arithmetic.
Select an answer for every question, then check the result and read each explanation. Progress remains in this browser; this is a self-check, not a judged program submission or a credential.
Common Mistakes
Component numbers are not stable business identifiers. A shortest-path result cannot ignore a negative cycle within its stated contract.