Laborator 10
distance(X,Y,List, Result) :- nth0(Index, List, X), nth0(Index2, List, Y),
R is Index2-Index, abs(R, Result).
path(S) :- S =[_,_,_,_],
distance(a,c,S,R1), distance(c,d,S,R2),
distance(b,d,S,R3), distance(b,c,S,R4),
R1>R2, R3>R4.
label(S) :- S=[p,t].
label2(S) :- S=[p,t]; S=[t,p].
label3(S) :- label(S), not(label2(S)) ;
label2(S), not(label(S)).
emperor(S) :- S = [_,_], label3(S).