236 lines
7.6 KiB
Scheme
236 lines
7.6 KiB
Scheme
;; The Computer Language Benchmarks Game
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;; http://shootout.alioth.debian.org/
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;;
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;; Based on a Python version:
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;; contributed by Olof Kraigher
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;; modified by Tupteq
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#lang scheme/base
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(require scheme/cmdline)
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(define width 5)
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(define height 10)
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(define (rotate dir)
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(case dir
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[(E) 'NE]
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[(NE) 'NW]
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[(NW) 'W]
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[(W) 'SW]
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[(SW) 'SE]
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[(SE) 'E]))
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(define (flip dir)
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(case dir
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[(E) 'W]
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[(NE) 'NW]
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[(NW) 'NE]
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[(W) 'E]
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[(SW) 'SE]
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[(SE) 'SW]))
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(define move
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(make-immutable-hash
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(list
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(cons 'E (lambda (x y) (values (add1 x) y)))
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(cons 'W (lambda (x y) (values (sub1 x) y)))
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(cons 'NE (lambda (x y) (values (+ x (bitwise-and y 1)) (sub1 y))))
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(cons 'NW (lambda (x y) (values (sub1 (+ x (bitwise-and y 1))) (sub1 y))))
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(cons 'SE (lambda (x y) (values (+ x (bitwise-and y 1)) (add1 y))))
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(cons 'SW (lambda (x y) (values (sub1 (+ x (bitwise-and y 1))) (add1 y)))))))
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(define move-procs
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(hash-map move (lambda (k v) v)))
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(define (valid? x y)
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(and (0 . <= . x)
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(x . < . width)
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(0 . <= . y)
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(y . < . height)))
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(define (clear? board pos)
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(not (bitwise-bit-set? board pos)))
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(define (set board pos)
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(bitwise-ior board (arithmetic-shift 1 pos)))
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(define (zero-count board)
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(for/fold ([count 0])
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([i (in-range (* width height))])
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(if (clear? board i)
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(add1 count)
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count)))
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(define (find-free-cell board)
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(let yloop ([y 0])
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(let xloop ([x 0])
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(if (= x width)
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(yloop (add1 y))
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(if (clear? board (+ x (* width y)))
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(values x y)
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(xloop (add1 x)))))))
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(define (flood-fill board x y)
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(if (valid? x y)
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(let ([pos (+ x (* y width))])
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(if (clear? board pos)
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(for/fold ([board (set board pos)])
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([move-proc move-procs])
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(let-values ([(x y) (move-proc x y)])
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(flood-fill board x y)))
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board))
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board))
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(define (no-islands? mask)
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(let ([zeros (zero-count mask)])
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(if (zeros . < . 5)
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#f
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(let loop ([mask mask][zeros zeros])
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(if (= mask #x3FFFFFFFFFFFF)
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#t
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(let*-values ([(x y) (find-free-cell mask)]
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[(mask) (flood-fill mask x y)]
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[(new-zeros) (zero-count mask)])
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(if ((- zeros new-zeros) . < . 5)
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#f
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(loop mask new-zeros))))))))
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(define (get-bitmask x y piece)
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(let ([mask (arithmetic-shift 1 (+ x (* y width)))])
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(let loop ([x x][y y][cells piece][mask mask])
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(if (null? cells)
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mask
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(let-values ([(x y) ((hash-ref move (car cells)) x y)])
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(if (valid? x y)
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(loop x y (cdr cells) (set mask (+ x (* width y))))
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#f))))))
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(define (all-bitmasks piece color)
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(let ([pieces
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(let-values ([(accum piece)
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(for/fold ([accum null] [piece piece])
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([orientations (in-range 2)])
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(let-values ([(accum piece)
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(for/fold ([accum accum] [piece piece])
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([orientations (in-range (- 6 (* 3 (if (= color 4)
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1
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0))))])
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(values (cons piece accum)
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(map rotate piece)))])
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(values accum (map flip piece))))])
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accum)])
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(for*/list ([piece (in-list pieces)]
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[y (in-range height)]
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[x (in-range width)]
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[mask (:do-in ([(mask) (get-bitmask x y piece)]) ; should be in-value
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#t () #t () #t #f ())]
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#:when (and mask (no-islands? mask)))
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mask)))
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(define (generate-bitmasks)
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(let ([pieces '((E E E SE)
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(SE SW W SW)
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(W W SW SE)
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(E E SW SE)
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(NW W NW SE SW)
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(E E NE W)
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(NW NE NE W)
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(NE SE E NE)
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(SE SE E SE)
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(E NW NW NW))]
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[masks-at-cell
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(list->vector
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(for/list ([i (in-range (* width height))])
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(list->vector
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(for/list ([j (in-range 10)])
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null))))])
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(for ([piece (in-list pieces)]
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[color (in-naturals)])
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(let loop ([masks (sort (all-bitmasks piece color) >)]
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[cell-bit (sub1 (* width height))]
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[cell-counter (sub1 (* width height))])
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(if (null? masks)
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masks-at-cell
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(if (bitwise-bit-set? (car masks) cell-bit)
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(let ([vec (vector-ref masks-at-cell cell-counter)])
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(vector-set! vec color (cons (car masks) (vector-ref vec color)))
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(loop (cdr masks) cell-bit cell-counter))
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(loop masks (sub1 cell-bit) (sub1 cell-counter))))))
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(for ([v (in-vector masks-at-cell)])
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(for ([j (in-naturals)]
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[val (in-vector v)])
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(vector-set! v j (reverse val))))
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masks-at-cell))
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(define masks-at-cell (generate-bitmasks))
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(define masks (make-vector 10 0))
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(define to-go 0)
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(define solutions null)
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(define (solve-cell! cell board)
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(when (and (positive? to-go)
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(not (negative? cell)))
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;; Need solutions and not off board
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(cond
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[(= board #x3FFFFFFFFFFFF)
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;; Solved
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(add-solutions!)]
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[(not (clear? board cell))
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;; Cell full, so try next
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(solve-cell! (sub1 cell) board)]
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[else
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;; Recur
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(for ([color (in-range 10)])
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(when (zero? (vector-ref masks color))
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(for ([mask (in-list (vector-ref
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(vector-ref masks-at-cell cell)
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color))])
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(when (zero? (bitwise-and mask board))
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(vector-set! masks color mask)
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(solve-cell! (sub1 cell) (bitwise-ior board mask))
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(vector-set! masks color 0)))))])))
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(define (add-solutions!)
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(let ([digits
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(for/list ([pos (in-range (* width height))])
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(for/or ([color (in-range 10)])
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(and (not (clear? (vector-ref masks color) pos))
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color)))])
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(let ([s (list->string
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(map (lambda (digit)
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(if digit
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(integer->char (+ digit (char->integer #\0)))
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#\.))
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digits))]
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[ns (make-string (* width height))])
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;; Inverse
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(for* ([y (in-range height)]
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[x (in-range width)])
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(string-set! ns (+ x (* y width))
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(string-ref s (+ (- width (+ x 1))
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(* width (- height (+ y 1)))))))
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;; Append
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(set! solutions (cons s solutions))
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(set! solutions (cons ns solutions))
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(set! to-go (- to-go 2)))))
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(define (print-solution solution)
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(for ([y (in-range height)])
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(for ([x (in-range width)])
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(display (string-ref solution (+ x (* y width))))
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(display " "))
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(display "\n")
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(when (even? y)
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(display " ")))
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(newline))
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(define (solve! n)
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(set! to-go n)
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(solve-cell! (sub1 (* width height)) 0))
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(command-line #:args (n) (solve! (string->number n)))
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(let ([solutions (sort solutions string<?)])
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(printf "~a solutions found\n\n" (length solutions))
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(print-solution (car solutions))
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(print-solution (list-ref solutions (sub1 (length solutions)))))
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