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38 lines
1.7 KiB
Racket
38 lines
1.7 KiB
Racket
2 years ago
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#lang br
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(require racket/file sugar rackunit racket/set)
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(define lines (map (λ (s) (map (λ (s2) (define ints (map string->number (string-split s2 ",")))
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(+ (first ints) (* +i (second ints)))) (string-split s " -> "))) (file->lines "05.rktd")))
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(define (Line-not-diagonal line)
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(match line
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[(list left right) (or (= (real-part left) (real-part right)) (= (imag-part left) (imag-part right)))]))
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;; why does make-polar cause the solution to run faster?
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;; both functions create an imaginary number
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;; make-polar is slower to create the numbers (because it has to call trig functions)
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;; but storing the polar numbers with frequency-hash is much faster
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;; using inexact coefficients makes make-rectangular go faster
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;; but still not as fast as make-polar
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(define go-fast? #true)
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(define imag-func (if go-fast? make-polar make-rectangular))
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(define (expand line)
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(match-define (list x1 x2) (map real-part line))
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(match-define (list y1 y2) (map imag-part line))
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(cond
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[(= x1 x2)
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(for/list ([i (in-range (apply min (list y1 y2)) (add1 (apply max (list y1 y2))))])
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(imag-func x1 i))]
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[(= y1 y2)
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(for/list ([i (in-range (apply min (list x1 x2)) (add1 (apply max (list x1 x2))))])
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(imag-func i y1))]
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[else (for/list ([x (in-range x1 ((if (> x1 x2) sub1 add1) x2) (if (> x1 x2) -1 1))]
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[y (in-range y1 ((if (> y1 y2) sub1 add1) y2) (if (> y1 y2) -1 1))])
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(imag-func x y))]))
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(define (calc-result points)
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(length (filter (λ (x) (>= x 2)) (hash-values (time (frequency-hash points))))))
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(check-equal? (calc-result (append-map expand (filter Line-not-diagonal lines))) 6113)
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(check-equal? (calc-result (append-map expand lines)) 20373)
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