% No looping approach, no duplicating

% states are simple atoms a, b, c, ... k.
% moves or successor states are directly hardwired into code

move(a,b).
move(a,c).
move(b,d).
move(b,e).
move(c,f).
move(c,g).
move(d,h).
move(h,d).
move(e,i).
move(e,j).
move(f,k).

start(a).
goal(j).
goal(f).

% Start with  ?- solve(a, Sol).

solve(X, Soln) :-
    solve(X, [], Sol),
    reverse(Sol, Soln).

% solve(State, Path, Solution)

solve(State, Path, [State|Path]) :-
    goal(State).

solve(State, Path, Sol) :-
    move(State, NewState),
    not(member(NewState, Path)),
    solve(NewState, [State|Path], Sol).