OJ Board

Got it. Turns out the spec is really not very clear. Just forget the "If it can not proceed, it will turn left until it can proceed.". The spec can be summarized as: "make the robot contour the map by always having a wall at its right side".

So after re-reading the problem 556 "Amazing", I still don't get how the robot is supposed to explore the environment. By (manually) following the algorithm described in the problem on the sample map, I would run into an infinite loop at the rightmost vertical corridor. Let "x" be the "trail" left ...