روش اول فرض می کنه که وزیر ها به صورت random رو صفحه قرار دارن و اونا رو مرتب می کنه
کدش اینه:
/* queens(N,Queens) :-
Queens is a placement that solves the N queens problem,
Represented as a permutation of the list of numbers [1,2,…,N]. */
queens(N,Qs) :- range(1,N,Ns), permutation(Ns,Qs), safe(Qs).
/* safe(Qs) :- the placement Qs is safe. */
safe([Q|Qs]) :- safe(Qs), not attack(Q,Qs).
safe([]).
attack(X,Xs) :- attack (X,1,Xs).
attack(X,N,[Y|Ys]) :- X is Y+N ; X is Y-N.
attack (X<N,[Y|Ys]) :- N1 is N+1, attack(X,N1,Ys).
permutation(Xs,[Z|Zs]) :- select(Z,Xs,Ys), permutation(Ys,Zs).
permutation([],[]).
select(X,[X|Xs],Xs).
select(X,[Y|Ys],[Y|Zs]) :- select(X,Ys,Zs).
range(M,N,[M|Ns]) :- M < N, M1 is M+1, range(M1,N,Ns).
range(N,N,[N]).
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