N-queens problem: Difference between revisions
Add emacs lisp
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11 Queen : 2680
12 Queen : 14200
</pre>
=={{header|Emacs Lisp}}==
<syntaxhighlight lang="lisp">
(let ((*result* '()))
(defun grid-cnt (n)
(* n n) )
(defun x-axis (n pos)
(/ pos n) )
(defun y-axis (n pos)
(% pos n) )
(defun chess-cnt (chess-map)
(seq-count (lambda (x) x) chess-map))
(defun check-conflict (n chess-map pos)
(let ((is-conflict nil))
(cl-loop for i from 0 to (1- (grid-cnt n)) while (not is-conflict) do
(when (aref chess-map i)
(when (or (= (x-axis n i) (x-axis n pos))
(= (y-axis n i) (y-axis n pos))
(= (abs (- (x-axis n i) (x-axis n pos)))
(abs (- (y-axis n i) (y-axis n pos))))
)
(setq is-conflict 't)
)
)
)
is-conflict )
)
(defun place-chess (n chess-map start-pos)
(if (< (chess-cnt chess-map) n)
(progn
(let ()
(cl-loop for i from start-pos to (1- (grid-cnt n)) do
(when (not (aref chess-map i)) ;; check if place is empty
;; check if place is on hold by other chess
(when (not (check-conflict n chess-map i))
(let ((map1 (copy-sequence chess-map)))
(aset map1 i 't)
(place-chess n map1 i)
)
)
)
)
)
)
(progn
(if *result* (nconc *result* (list chess-map)) (setq *result* (list chess-map)))
)
)
)
(defun show-result (n)
(let ()
(seq-map (lambda (map1)
(let ((map-txt ""))
(message ">>>>>>>>>>>>>>")
(seq-map-indexed (lambda (elm idx)
(if (= (% idx n) 0)
;;(setq map-text (concat map-txt "\n"))
(progn
(message map-txt)
(setq map-txt "") )
)
(setq map-txt
(concat map-txt (if elm "✓" "⓪")))
) map1)
(message "<<<<<<<<<<<<<<\n")
)
) *result*)
)
(message "totally %d solutions" (length *result*))
)
(defun start-calculate (n)
(let ((chess-map (make-vector (grid-cnt n) nil)))
(place-chess n chess-map 0)
)
(show-result n)
)
(start-calculate 8)
)
</syntaxhighlight>
<pre>
...
totally 92 solutions
</pre>
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