day 25: make it nicer

This commit is contained in:
xenia 2020-12-25 00:26:56 -05:00
parent f782867296
commit a37c076343
1 changed files with 10 additions and 33 deletions

43
25.rkt
View File

@ -1,51 +1,28 @@
#lang curly-fn racket
(require "scripts/aoc.rkt")
(require "scripts/aoc.rkt" math/number-theory)
;; solution for day 25
(define *mod* 20201227)
(define (loop subject times)
(for/fold ([val 1]) ([_ (in-range (+ 0 times))])
(remainder (* val subject) *mod*)))
(define *subject* 7)
(define (part1 input)
(match-define (list you door) input)
(define you-loops #f)
(define door-loops #f)
(for/fold ([val 1]) ([loops (in-range 0 +inf.0)] #:break (and you-loops door-loops))
(when (= val you)
(set! you-loops loops))
(when (= val door)
(set! door-loops loops))
(remainder (* val 7) *mod*))
; (displayln you-loops)
; (displayln door-loops)
(displayln you-loops)
(displayln (loop 7 you-loops))
(displayln you)
(displayln door-loops)
(displayln (loop 7 door-loops))
(displayln door)
; (displayln (loop door-loops you-loops))
; (displayln (loop you-loops door-loops))
; (displayln (loop 17807724 8))
; (displayln (loop 5764801 11))
(loop you door-loops))
; (part1 (list 5764801 17807724))
; (error)
(with-modulus *mod*
(for/fold ([val 1] [you-loops #f] [door-loops #f] #:result (modexpt you door-loops))
([loops (in-range 0 +inf.0)] #:break (and you-loops door-loops))
(define new-val (mod* val *subject*))
(cond
[(= val you) (values new-val loops door-loops)]
[(= val door) (values new-val you-loops loops)]
[else (values new-val you-loops door-loops)]))))
;; parse input file
(define (parse fname)
(define input (file->lines fname))
(map string->number input))
(module+ test
(require rackunit)
;; tests here
(displayln "no tests :("))
(module+ main
(define input (parse "inputs/25"))
(answer 25 1 (time (part1 input)))