Bike Map (Multi-part Route/Graph Problem)

Problem: Bike Map (Multi-part graph/path problem) You are given a grid or graph representing bike routes/terrain (exact modeling depends on the interviewer prompt). You need to implement 3 incremental parts. The original notes do not include the concrete input/output format or the exact requirements of each part, so the full prompt cannot be reliably reconstructed. In practice, such problems often involve shortest path / minimum-cost path, reachability, or path reconstruction, but the exact task must follow the actual prompt.