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.
64 lines
2.2 KiB
Racket
64 lines
2.2 KiB
Racket
8 years ago
|
#lang br/quicklang
|
||
|
|
;; http://adventofcode.com/2016/day/13
|
||
|
|
(require graph)
|
||
|
|
(provide read-syntax
|
||
|
|
(rename-out [mb #%module-begin]))
|
||
|
|
|
||
|
|
(define (read-syntax path port)
|
||
|
|
(strip-bindings
|
||
|
|
#`(module mod "lang.rkt"
|
||
|
|
#,(string->number (string-trim (port->string port))))))
|
||
|
|
|
||
|
|
(define-macro (mb NUM)
|
||
|
|
#'(#%module-begin
|
||
|
|
(solve 50 NUM)
|
||
|
|
(solve2 NUM)))
|
||
|
|
|
||
|
|
(define (solve dim num)
|
||
|
|
(define open? (make-open-pred num))
|
||
|
|
(define g (undirected-graph '((0 0))))
|
||
|
|
(for* ([x (in-range dim)]
|
||
|
|
[y (in-range dim)]
|
||
|
|
#:when (open? (list y x)))
|
||
|
|
(when (open? (list (add1 y) x))
|
||
|
|
(add-edge! g (list y x) (list (add1 y) x)))
|
||
|
|
(when (open? (list y (add1 x)))
|
||
|
|
(add-edge! g (list y x) (list y (add1 x)))))
|
||
|
|
(define path (fewest-vertices-path g '(1 1) '(31 39)))
|
||
|
|
(displayln (and path (sub1 (length path)))))
|
||
|
|
|
||
|
|
(define (solve2 num)
|
||
|
|
(define open? (make-open-pred num))
|
||
|
|
(define (nonnegative? pt) (and (not (negative? (car pt)))
|
||
|
|
(not (negative? (cadr pt)))
|
||
|
|
pt))
|
||
|
|
(let loop ([all-visited-pts empty]
|
||
|
|
[last-visited-pts '((1 1))]
|
||
|
|
[step 0])
|
||
|
|
(cond
|
||
|
|
[(= step 50)
|
||
|
|
(length (remove-duplicates (append all-visited-pts last-visited-pts)))]
|
||
|
|
[else
|
||
|
|
(loop (append last-visited-pts all-visited-pts)
|
||
|
|
(append*
|
||
|
|
(for/list ([lvp (in-list last-visited-pts)])
|
||
|
|
(match-define (list x y) lvp)
|
||
|
|
(for/list ([pt (in-list (list (list (add1 x) y)
|
||
|
|
(list x (add1 y))
|
||
|
|
(list (sub1 x) y)
|
||
|
|
(list x (sub1 y))))]
|
||
|
|
#:when (and (nonnegative? pt)
|
||
|
|
(open? pt)
|
||
|
|
(not (member pt all-visited-pts))))
|
||
|
|
pt)))
|
||
|
|
(add1 step))])))
|
||
|
|
|
||
|
|
(define (make-open-pred num)
|
||
|
|
(λ(pt)
|
||
|
|
(match-define (list x y) pt)
|
||
|
|
(define sum
|
||
|
|
(+ (* x x) (* 3 x) (* 2 x y) y (* y y) num))
|
||
|
|
(even?
|
||
|
|
(for/sum ([c (in-string (format "~b" sum))]
|
||
|
|
#:when (char=? #\1 c))
|
||
|
|
1))))
|