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#lang racket
(require data/queue)
(define data (for/list ([(n i) (in-indexed (file->list "day20-sterni"))])
(vector n i)))
(define (move zip n)
(cond [(= n 0) zip]
[(< n 0) (if (null? (car zip))
(move (cons (reverse (cdr zip)) '()) n)
(move (cons (cdr (car zip))
(cons (car (car zip)) (cdr zip)))
(+ n 1)))]
[(> n 0) (if (null? (cdr zip))
(move (cons '() (reverse (car zip))) n)
(move (cons (cons (car (cdr zip)) (car zip))
(cdr (cdr zip)))
(- n 1)))]))
(define (peek zip)
(if (null? (cdr zip))
(peek (move (move zip 1) -1))
(car (cdr zip))))
(define (zip->list zip)
(append (reverse (car zip)) (cdr zip)))
(define (find ring elt)
(let ([ring (move (move ring 1) -1)])
(if (equal? (vector-ref (peek ring) 1) elt)
ring
(find (move ring 1) elt))))
(define (find-val ring elt)
(let ([ring (move (move ring 1) -1)])
(if (equal? (vector-ref (peek ring) 0) elt)
ring
(find-val (move ring 1) elt))))
; (move (cons (list 1 2 3) (list 4 5 6)) 2)
; (move (move (cons (list 1 2 3) (list 4 5 6)) 100) -100)
(define ring (cons '() data))
(define (shift ring n)
(let* ([n (remainder n (- (length data) 1))]
[ring (move (move ring 1) -1)]
[e (peek ring)]
[ring (cons (car ring) (cdr (cdr ring)))] ; drop e
[ring (move ring n)]
[ring (cons (car ring) (cons e (cdr ring)))] ; insert e
[ring (move ring (- n 1))]
)
ring))
; (shift (cons (list #(1 1) #(2 2) #(3 3)) (list #(4 4) #(5 5) #(6 6))) 2)
(for ([(_ i) (in-indexed data)])
(set! ring (find ring i))
(set! ring (shift ring (vector-ref (peek ring) 0))))
(let* ([_ (set! ring (find-val ring 0))]
[_ (set! ring (move ring 1000))]
[a (vector-ref (peek ring) 0)]
[_ (set! ring (move ring 1000))]
[b (vector-ref (peek ring) 0)]
[_ (set! ring (move ring 1000))]
[c (vector-ref (peek ring) 0)])
(+ a b c))
;; 16533
(define data2 (for/list ([(n i) (in-indexed (file->list "day20"))])
(vector (* n 811589153) i)))
(define ring2 (cons '() data2))
(for ([_ (in-inclusive-range 1 10)])
(for ([(_ i) (in-indexed data2)])
(set! ring2 (find ring2 i))
(set! ring2 (shift ring2 (vector-ref (peek ring2) 0)))))
(zip->list ring2)
(let* ([_ (set! ring2 (find-val ring2 0))]
[_ (set! ring2 (move ring2 1000))]
[a (vector-ref (peek ring2) 0)]
[_ (set! ring2 (move ring2 1000))]
[b (vector-ref (peek ring2) 0)]
[_ (set! ring2 (move ring2 1000))]
[c (vector-ref (peek ring2) 0)])
(+ a b c))
;; 4789999181006
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