        \problemdata       % Takes 5 *mandatory* arguments
        {backtracking}             % latex-friendly label for the prob.
        {graphs}  % The topic(s) of the problem content.
        {Rosen \S 8.5 problem 28.}               % Source (if known)
        {F01 PS5-4} % Usage (list ones you are aware of).
        {}        % Last revision info (author, date).


\begin{problem}
%--------------------------------------
% source: rosen 8.5.28
% topics: backtracking, maze

Rosen \S 8.5 problem 28.

\solution{
We can use backtracking in the following way:
\begin{itemize}
\item Begin at the starting position and mark it as traveled.
\item At each stage, mark the current position and then chack the 4
  possible directions to go: up, down, right, left.  For each
  direction, check if the new position in that direction is not
  blocked and has not been traveled yet.
\item If there is a direction in which travel is possible, travel to
  the new position and repeat.
\item If travel is not possible in any of the four directions (because
  they're blocked or have been previously marked), then backtrack to
  the previous position and repeat.
\item Stop when we reach the exit
\end{itemize}
The path is fairly clear by inspection.
}

\end{problem}