Maze layout: # denotes a wall, . is an empty cell, A and B are robots. Use a rectangular grid with exactly one A and one B, and at most 24 open cells.

Two robots, one command

Bring A and B together in as few commands as possible. Each command is executed by both robots, but a wall or boundary keeps a robot in place.

Use arrow keys or buttons.

0 commands sent so far

Solution

Each node is an ordered pair (A, B) of cell numbers, denoting positions of respective robots. An arrow applies the same command to both robots. Green nodes have A = B. BFS explores from the start in increasing distance. Its tree gives a shortest route to every reachable pair. Bold green edges show all shortest routes from the start to the closest meeting nodes.

● meeting● current◎ start━ BFS tree━ shortest meeting routes