41 lines
1.3 KiB
Common Lisp
41 lines
1.3 KiB
Common Lisp
(defun queens1 (n)
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(let ((a (make-array n))
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(s (make-array n))
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(u (make-array (list (- (* 4 n) 2)) :initial-element t))
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y z (i 0) j p q (r (1- (* 2 n))) (m 0))
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(dotimes (i n) (setf (aref a i) i))
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(tagbody
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L1
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(if (>= i n) (go L5))
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(setf j i)
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L2
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(setf y (aref a j) z (aref a i))
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(setf p (+ (- i y) n -1) q (+ i y))
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(setf (aref a i) y (aref a j) z)
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(when (and (aref u p) (aref u (+ q r)))
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(setf (aref s i) j (aref u p) nil (aref u (+ q r)) nil)
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(incf i)
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(go L1))
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L3
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(incf j)
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(if (< j n) (go L2))
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L4
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(decf j)
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(if (= j i) (go L6))
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(rotatef (aref a i) (aref a j))
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(go L4)
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L5
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(incf m)
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L6
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(decf i)
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(if (minusp i) (go L7))
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(setf p (+ (- i (aref a i)) n -1) q (+ i (aref a i)) j (aref s i))
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(setf (aref u p) t (aref u (+ q r)) t)
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(go L3)
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L7)
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m))
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> (loop for n from 1 to 14 collect (cons n (queens1 n)))
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((1 . 1) (2 . 0) (3 . 0) (4 . 2) (5 . 10) (6 . 4) (7 . 40) (8 . 92) (9 . 352)
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(10 . 724) (11 . 2680) (12 . 14200) (13 . 73712) (14 . 365596))
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