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|
#lang racket
(define pieces
'(#(#(#t #t #t #t))
#(#(#f #t #f)
#(#t #t #t)
#(#f #t #f))
#(#(#f #f #t)
#(#f #f #t)
#(#t #t #t))
#(#(#t)
#(#t)
#(#t)
#(#t))
#(#(#t #t)
#(#t #t))
))
(define piece-height vector-length)
(define (piece-width p) (vector-length (vector-ref p 0)))
(define input (list->vector (string->list (car (file->lines "day17")))))
(define stack #())
(define (piece-fit stack piece offset-height offset-width)
(for/and ([h (in-range 0 (piece-height piece))])
(for/and ([w (in-range 0 (piece-width piece))])
(if (and (< -1 (+ offset-height h) (vector-length stack))
(< -1 (+ offset-width w) 7))
(if (equal? #t (vector-ref (vector-ref piece h) w))
(equal? #f (vector-ref (vector-ref stack (+ offset-height h)) (+ offset-width w)))
#t)
#f))))
(define (piece-place stack piece offset-height offset-width)
(for ([h (in-range 0 (piece-height piece))])
(for ([w (in-range 0 (piece-width piece))])
(when (and (< -1 (+ offset-height h) (vector-length stack))
(< -1 (+ offset-width w) 7)
(equal? #t (vector-ref (vector-ref piece h) w)))
(vector-set! (vector-ref stack (+ offset-height h)) (+ offset-width w) #t)))))
(define (drop-piece piece)
(set! stack (vector-append (build-vector (+ 3 (piece-height piece))
(lambda (_)
(make-vector 7 #f)))
stack))
(let ([offset-height 0]
[offset-width 2])
(let loop ()
(let ([move (if (equal? (next-move) #\<) -1 1)])
(when (piece-fit stack piece offset-height (+ offset-width move))
(set! offset-width (+ offset-width move)))
(when (piece-fit stack piece (+ 1 offset-height) offset-width)
(set! offset-height (+ offset-height 1))
(loop))))
(piece-place stack piece offset-height offset-width)
(let loop2 ([empty-height 0])
(if (vector-member #t (vector-ref stack empty-height))
(when (> empty-height 0)
(set! stack (vector-drop stack empty-height)))
(loop2 (+ 1 empty-height)))))
)
(define next-move
(let ([i 0]
[s (vector-length input)])
(lambda ()
(let ([r (vector-ref input (remainder i s))])
(set! i (+ 1 i))
r))))
(for ([_ (in-inclusive-range 1 2022)]
[piece (in-cycle pieces)])
(drop-piece piece))
(vector-length stack)
;; 3067
; stare at the output
;; 1514369501484
|
