Robot Mouse Program

• The maze is a 2-D array. * represents a wall. 0 represents an open space. c represents cheese.

• The mouse starts in an open position.

• The mouse has 4 possible moves at each point: w, n, e or s.

• We have to keep track of where the mouse has been, or it might wander infinitely in circles. The list prev is a stack of previous states. If the mouse re-visits a position on prev, we want to fail.

• We need to return an answer:
  • nil for failure

  • a list of moves that will lead from the current position to the goal; for the goal itself, we return (). As we unwind the recursion, we will push the operator that led to the goal onto the answer list at each step.