67 lines
1.8 KiB
Racket
67 lines
1.8 KiB
Racket
#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 12
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;; helper functions here
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(define (d->r deg)
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(* (/ deg 180) pi))
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(define (part1 input)
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(define-values [dir x y]
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(for/fold ([dir 0] [x 0] [y 0]) ([ins (in-list input)])
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(match-define (cons ltr num) ins)
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(match ltr
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["N" (values dir x (+ y num))]
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["S" (values dir x (- y num))]
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["E" (values dir (+ x num) y)]
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["W" (values dir (- x num) y)]
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["L" (values (+ dir (d->r num)) x y)]
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["R" (values (- dir (d->r num)) x y)]
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["F" (values dir (+ x (* num (cos dir))) (+ y (* num (sin dir))))])))
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(inexact->exact (floor (+ (abs x) (abs y)))))
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(define (part2 input)
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(define (rot x y d)
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(values
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(- (* x (cos d)) (* y (sin d)))
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(+ (* x (sin d)) (* y (cos d)))))
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(define-values [sx sy wx wy]
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(for/fold ([sx 0] [sy 0] [wx 10] [wy 1]) ([ins (in-list input)])
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(match-define (cons ltr num) ins)
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(match ltr
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["N" (values sx sy wx (+ wy num))]
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["S" (values sx sy wx (- wy num))]
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["E" (values sx sy (+ wx num) wy)]
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["W" (values sx sy (- wx num) wy)]
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["L"
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(define-values [nwx nwy] (rot wx wy (d->r num)))
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(values sx sy nwx nwy)]
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["R"
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(define-values [nwx nwy] (rot wx wy (d->r (- num))))
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(values sx sy nwx nwy)]
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["F"
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(values (+ sx (* num wx)) (+ sy (* num wy)) wx wy)])))
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(inexact->exact (floor (+ (abs sx) (abs sy)))))
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(module+ test
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(require rackunit)
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;; tests here
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(displayln "no tests :("))
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(module+ main
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(define input
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(for/list ([line (in-list (file->lines "inputs/12"))])
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(match line
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[(pregexp #px"^(.)([0-9]+)$" (list _ dir (app string->number num)))
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(cons dir num)])))
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;; part 1
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(answer 12 1 (part1 input))
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;; part 2
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(answer 12 2 (part2 input))
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(displayln "meow"))
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