68 lines
2.2 KiB
Racket
68 lines
2.2 KiB
Racket
#lang racket
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(struct vec [x y z] #:transparent)
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(define (vec->list v) (list (vec-x v) (vec-y v) (vec-z v)))
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(define (vec+ . vecs)
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(define x (apply + (map vec-x vecs)))
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(define y (apply + (map vec-y vecs)))
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(define z (apply + (map vec-z vecs)))
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(vec x y z))
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(define lines (string-split (string-trim (file->string "input.12.txt")) "\n"))
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(define (parse-line line)
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(map string->number (regexp-match* #rx"[0-9\\-]+" line)))
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(define input (map (compose (curry apply vec) parse-line) lines))
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(define (bound val)
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(cond [(negative? val) -1]
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[(positive? val) 1]
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[else 0]))
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(define (gravity-axis val1 val2)
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(bound (- val2 val1)))
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(define (gravity-axis-all lop pos)
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(apply + (map (curry gravity-axis pos) lop)))
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(define (gravity pos1 pos2)
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(apply vec (map gravity-axis (vec->list pos1) (vec->list pos2))))
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(define (gravity-all lop pos)
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(apply vec+ (map (curry gravity pos) lop)))
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(define (initial-vels lop)
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(map (lambda (x) (vec 0 0 0)) lop))
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(define (sim-step lop [lov (initial-vels lop)])
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(define loa (map (curry gravity-all lop) lop))
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(define new-lov (map vec+ lov loa))
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(define new-lop (map vec+ lop new-lov))
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(list new-lop new-lov))
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(define (energy v)
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(apply + (map abs (vec->list v))))
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(define final-state (for/foldr ([state (list input (initial-vels input))])
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([i (in-range 1000)])
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(apply sim-step state)))
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;; Functional heckcode time
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;; (Sorry lol)
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(apply + (apply map * (map (curry map energy) final-state)))
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(define (sim-step-axis lop [lov (map (lambda (x) 0) lop)])
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(define loa (map (curry gravity-axis-all lop) lop))
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(define new-lov (map + lov loa))
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(define new-lop (map + lop new-lov))
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(list new-lop new-lov))
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(define (find-repeat-axis initial-lop [lop initial-lop] [lov (map (lambda (x) 0) lop)] [acc 1])
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(define next-state (sim-step-axis lop lov))
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(cond
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[(and (equal? initial-lop (first next-state)) (andmap zero? (second next-state))) acc]
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[else (find-repeat-axis initial-lop (first next-state) (second next-state) (add1 acc))]))
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(define repeat-x (find-repeat-axis (map vec-x input)))
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(define repeat-y (find-repeat-axis (map vec-y input)))
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(define repeat-z (find-repeat-axis (map vec-z input)))
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(lcm repeat-x repeat-y repeat-z) |