n-queens 問題をスキームで解決しようとしています。私は教授から、ベクトルの i 番目の要素がボードの i 番目の列を表す単一のベクトルをチェス盤として使用するように言われました。その要素の値は、クイーンが置かれている行、または列が空の場合は -1 です。したがって、[0 1 2 -1 -1] には、クイーンのない 2 つの列と、不正に配置された 3 つのクイーンがあります。このコードを実行すると: (place-n-queens 0 4 #(-1 -1 -1 -1)) #(0 1 2 3) が得られます。明らかに 4 つのクイーンすべてが不正に配置されています。問題は、place-queen-on-n の cond で十分なものをチェックしていないことだと思いますが、同じ対角線上にクイーンを配置するという問題を解決するために何を追加すればよいかわかりません。
(define (return-row vector queen)
(vector-ref vector (return-col vector queen)))
(define (return-col vector queen)
(remainder queen (vector-length vector)))
(define (checkrow vector nq oq)
(cond
((= (vector-ref vector nq) -1) #f)
((= (vector-ref vector oq) -1) #f)
(else (= (return-row vector nq) (return-row vector oq)))))
(define (checkcol vector nq oq)
(= (return-col vector nq) (return-col vector oq)))
(define (checkdiagonal vector nq oq)
(cond
((= (vector-ref vector nq) -1) #f)
((= (vector-ref vector oq) -1) #f)
(else (= (abs (- (return-row vector nq) (return-row vector oq)))
(abs (- (return-col vector nq) (return-col vector oq)))))))
(define (checkdiagonalagain vector r c oq)
(= (abs (- r (return-row vector oq)))
(abs (- c (return-col vector oq)))) )
(define (checkrowagain vector r oq)
(= r (return-row vector oq)))
(define (checkinterference vector nq oq)
(or (checkrow vector nq oq) (checkcol vector nq oq) (checkdiagonal vector nq oq)))
(define (place-queen-on-n vector r c)
(local ((define (foo x)
(cond
((checkrowagain vector r x) -1)
((= c x) r)
((checkinterference vector c x) -1)
((map (lambda (y) (eq? (vector-ref vector x) y))
(build-list (vector-length vector) values)) (vector-ref vector x))
((eq? (vector-ref vector x) -1) -1)
(else -1))))
(build-vector (vector-length vector) foo)))
(define (place-a-queen vector)
(local ((define (place-queen collist rowlist)
(cond
((empty? collist) '())
((empty? rowlist) '())
(else (append (map (lambda (x) (place-queen-on-n vector x (car collist))) rowlist)
(try vector (cdr collist) rowlist)))
)))
(place-queen (get-possible-col vector) (get-possible-row (vector->list vector) vector))))
(define (try vector collist rowlist)
(cond
((empty? collist) '())
((empty? rowlist) '())
(else (append (map (lambda (x) (place-queen-on-n vector x (car collist))) rowlist)
(try vector (cdr collist) rowlist)))))
(define (get-possible-col vector)
(local ((define (get-ava index)
(cond
((= index (vector-length vector)) '())
((eq? (vector-ref vector index) -1)
(cons index (get-ava (add1 index))))
(else (get-ava (add1 index))))))
(get-ava 0)))
;list is just vector turned into a list
(define (get-possible-row list vector)
(filter positive? list)
(define (thislist) (build-list (vector-length vector) values))
(remove* list (build-list (vector-length vector) values))
)
(define (place-n-queens origination destination vector)
(cond
((= origination destination) vector)
(else (local ((define possible-steps
(place-n-queens/list (add1 origination)
destination
(place-a-queen vector))))
(cond
((boolean? possible-steps) #f)
(else possible-steps))))))
(define (place-n-queens/list origination destination boards)
(cond
((empty? boards) #f)
(else (local ((define possible-steps
(place-n-queens origination destination (car boards))))
(cond
((boolean? possible-steps) (place-n-queens/list origination destination (cdr boards)))
(else possible-steps))
))))
これを機能させるために、どんな助けでも大歓迎です!!