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25 lines
945 B
Racket
25 lines
945 B
Racket
6 years ago
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#lang br
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(require "aima.rkt" sugar/debug)
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;; queens problem
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;; place queens on chessboard so they do not intersect
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(define qs (for/list ([q 8]) (string->symbol (format "q~a" q))))
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(define rows (range (length qs)))
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(define vds (for/list ([q qs])
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($vd q (range (length qs)))))
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(define (q-col q) (string->number (string-trim (symbol->string q) "q")))
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(define cs (for*/list ([qs (in-combinations qs 2)])
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(match-define (list qa qb) qs)
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(match-define (list qa-col qb-col) (map q-col qs))
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($constraint
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(list qa qb)
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(λ (qa-row qb-row)
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(and
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(not (= (abs (- qa-row qb-row)) (abs (- qa-col qb-col)))) ; same diagonal?
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(not (= qa-row qb-row)))))))
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(define queens (make-csp vds cs))
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(current-solver min-conflicts)
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(time-named (solve queens))
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