%	dfs.pl

% naive attemp!  Solution path found couldbe be 20,000
%                steps away instead of just 4 or 5.

% This predicate helps you choose a starting state and 
% displays the eventual solution path
dfs :-	write('Start at depth 4 5 6 7 8 or 18 ?  : '),
	read( I ),
	start( I , X ),
	dfs( X, [], Sol ),
    reverse(Sol, Soln), 
	nl, showSolPath( Soln).

% This predicate helps you choose a starting state and 
% displays the lenght of the eventual solution path.
% More useful here.
dfs2 :-	write('Start at depth 4 5 6 7 8 or 18 ?  : '),
	read( I ),
	start( I , X ),
	dfs( X, [], Sol ),
    length(Sol, L), nl,
    write('Solution requires '), write(L), write(' steps'), nl.
    
% This is the central predicate for depth first search
% Same as solve(X, P, S) in notes    
dfs( X , P , [X | P] ) :- goal( X ).
dfs( X , P , S ) :-
	move( X , X1 ),
    not(member(X1, P)),
	dfs( X1 , [X|P] , S ).