/* PLAN - program znajdowania trasy polaczen miedzy miastami */
%%% Przeszukiwanie wgłąb z nawrotami


     droga(krakow,katowice).
     droga(katowice,opole).
     droga(wroclaw,opole).
     droga(krakow,zakopane).
     droga(krakow,kielce).
     droga(krakow,tarnow).
     droga(kielce,radom).
     droga(radom,warszawa).
     droga(warszawa,poznan).
     droga(warszawa,gdansk).
     droga(warszawa,lodz).
     droga(poznan,szczecin).
     droga(poznan,wroclaw).
     droga(tarnow,rzeszow).
     droga(rzeszow,lublin).
     droga(lublin,bialystok).
     droga(warszawa,bialystok).
     droga(szczecin,koszalin).
     droga(koszalin,gdansk).

%%% domknięcie symetryczne relacji droga/2
     
     przejazd(X,Y):- droga(X,Y).
     przejazd(X,Y):- droga(Y,X).
     
     p(X,Y):- przejazd(X,Y).

%%% Depth-First Strategy:

    path(F,F,T,T).                %%% A path from F to F is defined the current working path T
    path(I,F,Path,T):-            %%% A path from I to F where Path is the current path
       p(I,N), %write(N), nl,      %%% Find a new node N
       not(member(N,Path)),       %%% Check for ne cycle
       path(N,F,[N|Path],T).      %%% A Path from N to F - the last before F

    go(I,F,Path):-
       path(I,F,[I],Path).

%%% Depth-First Strategy with calculating the depth

    path(F,F,T,T,D,D).                %%% A path from F to F is defined the current working path T
    path(I,F,Path,T,L,D):-            %%% A path from I to F where Path is the current path
       p(I,N), %write(N), nl,      %%% Find a new node N
       not(member(N,Path)),         %%% Check for ne cycle
       L1 is L+1,     
       path(N,F,[N|Path],T,L1,D).      %%% A Path from N to F - the last before F

    godc(I,F,Path,D):-
       path(I,F,[I],Path,1,D).