Maze routing
Beginner
Finding a path through a grid with obstacles by spreading outward step by step from the start until you reach the goal, like water flooding a maze.
Novice
Finding a path through a grid with obstacles by spreading out from the start one step at a time, labeling each point with its distance, until the target is reached, then tracing back along falling labels. It always finds a path if one exists, but may visit a great many grid points.
Expert
Lee’s breadth-first wave expansion, generalized to Dijkstra for weighted costs and to A* with a distance-to-target estimate. It is the core search in both global (GCell graph) and detailed (track graph) routers. Variants trade optimality for speed: Hadlock’s detour numbers, Soukup’s line-then-wave search, bidirectional search, and limiting the search to a box around the pins.