2024-02-22 01:07:29 -05:00
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between(I, J, K) :-
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I =< J,
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( I = K
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; I1 is I+1,
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between(I1, J, K)
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).
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2024-02-21 23:53:58 -05:00
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legal_queens(N, Row, []) :- N =:= Row - 1.
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legal_queens(N, Row1, [(Row1, Col1)|Queens]) :-
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Row1 < N + 1,
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Row2 is Row1 + 1,
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legal_queens(N, Row2, Queens),
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between(1,N,Col1),
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no_attacks((Row1, Col1), Queens).
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no_attacks(_, []).
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no_attacks((Row1, Col1), [(Row2, Col2)|OtherQueens]) :-
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Row1 \= Row2,
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Col1 \= Col2,
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abs(Row1 - Row2) =\= abs(Col1 - Col2),
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no_attacks((Row1, Col1), OtherQueens).
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n_queens(N, Solution) :-
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legal_queens(N, 1, Solution).
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one_queens(N, Solution) :-
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legal_queens(N, 1, Solution), !.
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printNQueen(N) :- n_queens(N, Solution), write(Solution), write('\n'), fail.
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printNQueen(_).
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printOneQueen(N) :- one_queens(N, Solution), write(Solution), write('\n'), fail.
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printOneQueen(_).
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timeNQueen(N) :- cputime(X), printNQueen(N), cputime(Y), T is Y-X, write(T).
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timeOneQueen(N) :- cputime(X), printOneQueen(N), cputime(Y), T is Y-X, write(T).
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