You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
34 lines
1.0 KiB
Racket
34 lines
1.0 KiB
Racket
#lang br/quicklang ;; http://adventofcode.com/2016/day/18
|
|
(provide read-syntax
|
|
(rename-out [mb #%module-begin]))
|
|
|
|
(define (read-syntax path port)
|
|
(strip-bindings
|
|
#`(module mod "lang.rkt"
|
|
#,(string-trim (port->string port)))))
|
|
|
|
(define-macro (mb NUM-STR)
|
|
#'(#%module-begin
|
|
#;(displayln (solve (string->number NUM-STR) #f))
|
|
(displayln (solve (string->number NUM-STR) #t))))
|
|
|
|
(define (idx-after vec x)
|
|
(or
|
|
(for/first ([idx (in-range (modulo (add1 x) (vector-length vec)) (vector-length vec))]
|
|
#:when (vector-ref vec idx))
|
|
idx)
|
|
(idx-after vec -1)))
|
|
|
|
(define (solve num [circle? #f])
|
|
(define elves (make-vector num #t))
|
|
(let loop ([taker 0][elves-left num])
|
|
(cond
|
|
[(= elves-left 2) (add1 taker)]
|
|
[else
|
|
(define giver (for/fold ([elf taker])
|
|
([i (in-range (if circle? (floor (/ elves-left 2)) 1))])
|
|
(idx-after elves elf)))
|
|
(vector-set! elves giver #f)
|
|
(loop (idx-after elves taker) (sub1 elves-left))])))
|
|
|