我想找到从A站到B站的路径，但这种路径有点工作，我提出的路径到处都是，它有时会在两个站点之间来回走动回到上一点，然后超出B站并返回到它，在路径中给我重复和不需要的站点。
我注意到的一件事可能是某些工作站是具有相同名称但其上有不同线路的交换站的问题。这些是电弧站：
%adjecent stations %
% Central line
adjacent(nh,lg,central,4).
adjacent(lg,oc,central,4).
adjacent(oc,tc,central,4).
adjacent(tc,cl,central,4).
adjacent(cl,ls,central,4).
adjacent(ls,bg,central,4).
% Victoria Line
adjacent(br,vi,victoria,4).
adjacent(vi,oc,victoria,4).
adjacent(oc,ws,victoria,4).
adjacent(ws,kx,victoria,4).
adjacent(kx,fp,victoria,4).
% Northern Line
adjacent(ke,em,northern,4).
adjacent(em,tc,northern,4).
adjacent(tc,ws,northern,4).
adjacent(ws,eu,northern,4).
% Metropolitan Line
adjacent(al,ls,metropolitan,4).
adjacent(ls,kx,metropolitan,4).
adjacent(bs,fr,metropolitan,4).
% Bakerloo Line
adjacent(ec,em,bakerloo,4).
adjacent(em,oc,bakerloo,4).
adjacent(oc,pa,bakerloo,4).
adjacent(pa,wa,bakerloo,4).
......以及这里的规则：
next(X,Y,L):-adjacent(X,Y,L,_).
next(X,Y,L):-adjacent(Y,X,L,_).
direct_connect(X,Y,L,S,F):-
next(X,Z,L),
not(member(Z,S)),
direct_connect(Z,Y,L,[Z|S],F).
direct_connect(X,Y,L,S,[Y|S]):- next(X,Y,L).
one_change(X,Y,L,F):-
direct_connect(X,Z,L,[X],F1),
direct_connect(Z,Y,L2,[Z|F1],F),
L\=L2.
exist(X):-next(X,_,_).
member(X,[X|_]).
member(X,[_|T]):-member(X,T).
route(X,Y,F):-exist(X),exist(Y),
direct_connect(X,Y,_,[X],F),
write('Direct Connection'),nl,
revwrite(F).
route(X,Y,F):-exist(X),exist(Y),
one_change(X,Y,_,F),
write('One change required'),nl,
revwrite(F).
revwrite([X]):-write(X).
revwrite([H|T]):-revwrite(T), write('->'),write(H).
测试用例：
route(em,ls,Route).
...我得到的输出是：
One change required
em->tc->ws->tc->tc->cl->ls->bg->ls
Route = [ls, bg, ls, cl, tc, tc, ws, tc, em]
我不明白为什么我会得到副本。我怎样才能避免偏离路线，回来，走遍各地？
答案 0 :(得分：1)
问题（至少有一个问题）在direct_connect/5;在以下条款中
direct_connect(X,Y,L,S,F):-
next(X,Z,L),
not(member(Z,S)),
direct_connect(Z,Y,L,[Z|S],F).
您并未强制Z与Y不同。
建议：按如下方式修改，强加Z \= Y
direct_connect(X,Y,L,S,F):-
next(X,Z,L),
Z \= Y,
not(member(Z,S)),
direct_connect(Z,Y,L,[Z|S],F).