Programming an A.I.

I need help programming an A.I. for motion planning. i have basic knowledge and experience with A.I.s on a 2d scale. Also I am fairly knowledgeable with Alice. I need the A.I.s to be able to compute the shortest path through rooms and hallways. In my 2d game maker, I used a motion planning grid. Can anyone help me do something similar. Any info is helpful, thanks.