master
Matthew Butterick 5 years ago
parent bbfca5f2a4
commit f85815ea65

@ -6,32 +6,28 @@
(define lines (port->lines port))
(strip-context #`(module mod "main.rkt"
#,@(for/list ([datum (in-port read (open-input-string (car lines)))])
datum)
datum)
#,@(cdr lines))))
(define-macro (#%mb STARS LINE ...)
#'(#%module-begin
(time (STARS (list LINE ...)))))
(define (populate-hash! chars lines)
(for* ([(line lidx) (in-indexed lines)]
[(c cidx) (in-indexed (string->list line))]
#:unless (char=? c #\space))
(hash-set! chars (+ lidx (* +i cidx)) c)))
(define (traverse lines #:count-steps [count-steps? #f])
(define chars (make-hasheqv))
(populate-hash! chars lines)
(define chars (for*/hasheqv ([(line lidx) (in-indexed lines)]
[(c cidx) (in-indexed (string->list line))]
#:unless (char=? c #\space))
(values (+ lidx (* +i cidx)) c)))
(define start (for/first ([k (in-hash-keys chars)]
#:when (zero? (real-part k)))
k))
k))
(define down 1) (define up -1) (define left -i) (define right +i)
(let loop ([here start][dir down][path null])
(define here-char (hash-ref chars here #f))
(cond
[here-char
(define next-dir (if (char=? here-char #\+)
(if (hash-has-key? chars (+ here (* dir +i))) (* dir +i) (* dir -i))
(if (hash-has-key? chars (+ here (* dir right))) (* dir right) (* dir left))
dir))
(loop (+ here next-dir) next-dir (cons here-char path))]
[count-steps? (length path)]