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day 12: rewrite using complex numbers

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xenia 2020-12-12 00:54:22 -05:00
parent a612240e50
commit f8f7363dba
1 changed files with 24 additions and 39 deletions
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63
12.rkt
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@ -6,50 +6,35 @@
;; helper functions here
(define (d->r deg)
(* (/ deg 180) pi))
(define d->r degrees->radians)
(define (part1 input)
(define-values [dir x y]
(for/fold ([dir 0] [x 0] [y 0]) ([ins (in-list input)])
(match-define (cons ltr num) ins)
(match ltr
["N" (values dir x (+ y num))]
["S" (values dir x (- y num))]
["E" (values dir (+ x num) y)]
["W" (values dir (- x num) y)]
["L" (values (+ dir (d->r num)) x y)]
["R" (values (- dir (d->r num)) x y)]
["F" (values dir (+ x (* num (cos dir))) (+ y (* num (sin dir))))])))
(inexact->exact (floor (+ (abs x) (abs y)))))
(define (part2 input)
(define (rot x y d)
(values
(- (* x (cos d)) (* y (sin d)))
(+ (* x (sin d)) (* y (cos d)))))
(define-values [sx sy wx wy]
(for/fold ([sx 0] [sy 0] [wx 10] [wy 1]) ([ins (in-list input)])
(define-values [dir s]
(for/fold ([dir 0] [s 0]) ([ins (in-list input)])
(match-define (cons ltr num) ins)
(match ltr
["N" (values sx sy wx (+ wy num))]
["S" (values sx sy wx (- wy num))]
["E" (values sx sy (+ wx num) wy)]
["W" (values sx sy (- wx num) wy)]
["L"
(define-values [nwx nwy] (rot wx wy (d->r num)))
(values sx sy nwx nwy)]
["R"
(define-values [nwx nwy] (rot wx wy (d->r (- num))))
(values sx sy nwx nwy)]
["F"
(values (+ sx (* num wx)) (+ sy (* num wy)) wx wy)])))
(inexact->exact (floor (+ (abs sx) (abs sy)))))
["N" (values dir (+ s (* +i num)))]
["S" (values dir (- s (* +i num)))]
["E" (values dir (+ s num))]
["W" (values dir (- s num))]
["L" (values (+ dir (d->r num)) s)]
["R" (values (- dir (d->r num)) s)]
["F" (values dir (+ s (make-polar num dir)))])))
(inexact->exact (round (+ (abs (real-part s)) (abs (imag-part s))))))
(module+ test
(require rackunit)
;; tests here
(displayln "no tests :("))
(define (part2 input)
(define-values [s w]
(for/fold ([s 0] [w 10+1i]) ([ins (in-list input)])
(match-define (cons ltr num) ins)
(match ltr
["N" (values s (+ w (* +i num)))]
["S" (values s (- w (* +i num)))]
["E" (values s (+ w num))]
["W" (values s (- w num))]
["L" (values s (* w (make-polar 1 (d->r num))))]
["R" (values s (* w (make-polar 1 (d->r (- num)))))]
["F" (values (+ s (* w num)) w)])))
(inexact->exact (round (+ (abs (real-part s)) (abs (imag-part s))))))
(module+ main
(define input