master
Matthew Butterick 6 years ago
parent 379cd904b5
commit 10fd78b85a

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#lang reader "../aoc-lang.rkt"
(require racket/sequence)
(provide (rename-out [#%mb #%module-begin]))
(define-macro (#%mb (STARS) (STR) ...)
#`(#%module-begin
((if (eq? 'STARS ') one-star (λ (x) #f)) (format "~a" 'STR)) ...))
(define (one-star str)
(for*/sum ([i (in-range 128)]
[digit (in-list (kh->ints (knot-hash (format "~a-~a" str i))))])
digit))
(define (kh->ints kh)
(for*/list ([c (in-string kh)]
[num (in-value (string->number (string c) 16))]
[c (in-string (~r num #:base 2 #:min-width 4 #:pad-string "0"))])
(string->number (string c))))
(define (knot-hash seed-str [range-in 256])
(define ascii-chars (map char->integer (string->list seed-str)))
(define nums (reverse-segments range-in (append ascii-chars '(17 31 73 47 23)) #:reps 64))
(define dense-hash (for/list ([vals (in-slice 16 nums)])
(apply bitwise-xor vals)))
(string-append* (for/list ([num (in-list dense-hash)])
(~r num #:base 16 #:min-width 2 #:pad-string "0"))))
(define (reverse-segments range-in lens #:reps [reps 1])
(define vec (list->vector (range range-in)))
(for*/fold ([current-position 0]
[skip-size 0])
([rep (in-range reps)]
[len (in-list lens)])
(define posns (for/list ([i (in-range len)])
(modulo (+ current-position i) range-in)))
(for ([val (in-list (map (curry vector-ref vec) posns))]
[posn (in-list (reverse posns))])
(vector-set! vec posn val))
(values (+ current-position len skip-size) (add1 skip-size)))
(vector->list vec))

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#lang reader "main.rkt" ; 8214
hxtvlmkl

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#lang reader "main.rkt" ; 8108
flqrgnkx