Next Station

Establish what a station means

Ask whether stations form one ordered line, a directed transit graph, or a timetable; whether the request is for the immediate neighbor, the next reachable stop, or the fastest next stop; and whether transfers, time, and capacity matter. A route list allows direct indexing, while an unweighted network calls for BFS and a weighted travel-time network calls for Dijkstra's algorithm.

Restate the model and give the simplest correct baseline. For an unweighted graph, BFS visits nodes by hop count in O(V + E) time and O(V) space. For nonnegative weighted edges, a binary heap Dijkstra implementation is typically O((V + E) log V). Validate unreachable stations, cycles, duplicate edges, one-station routes, and whether schedules make an edge time-dependent. Do not claim a fixed algorithm from the phrase alone. A good interview answer explains which clarification switches the algorithm and why, then names the traversal invariant such as finalized shortest distance.