diff options
Diffstat (limited to '10')
| -rw-r--r-- | 10/1.rkt | 83 | ||||
| -rw-r--r-- | 10/2.rkt | 112 |
2 files changed, 195 insertions, 0 deletions
diff --git a/10/1.rkt b/10/1.rkt new file mode 100644 index 0000000..3d9801c --- /dev/null +++ b/10/1.rkt @@ -0,0 +1,83 @@ +#lang racket + +(require "../lib/utils.rkt") + +(define lines + (call-with-input-file "input" + (λ (fp) + (get-lines fp)))) + +(define diagram (list->vector lines)) +(define height (vector-length diagram)) +(define width (string-length (vector-ref diagram 0))) +(define (char-at x y) + (string-ref (vector-ref diagram y) x)) + +(define (find-start) + (let loop ((x 0) (y 0)) + (if (>= y height) + #f + (if (>= x width) + (loop 0 (+ y 1)) + (if (char=? #\S (char-at x y)) + (cons x y) + (loop (+ x 1) y)))))) + +(define start (find-start)) + +(define (valid-pos? pos) + (define x (car pos)) + (define y (cdr pos)) + (and (and (>= x 0) (< x width)) + (and (>= y 0) (< y height)))) + +(define first-pos + (let () + (define up (cons (car start) (- (cdr start) 1))) + (define down (cons (car start) (+ (cdr start) 1))) + (define left (cons (- (car start) 1) (cdr start))) + (define right (cons (+ (car start) 1) (cdr start))) + (cond ((and (valid-pos? up) + (member (char-at (car up) (cdr up)) (list #\| #\F #\7))) + up) + ((and (valid-pos? down) + (member (char-at (car down) (cdr down)) (list #\| #\L #\J ))) + down) + ((and (valid-pos? left) + (member (char-at (car left) (cdr left)) (list #\- #\F #\L ))) + left) + ((and (valid-pos? right) + (member (char-at (car right) (cdr right)) (list #\- #\7 #\J))) + right)))) + +(define (next cur recent) + (define up (cons (car cur) (- (cdr cur) 1))) + (define down (cons (car cur) (+ (cdr cur) 1))) + (define left (cons (- (car cur) 1) (cdr cur))) + (define right (cons (+ (car cur) 1) (cdr cur))) + (define c (char-at (car cur) (cdr cur))) + (define possible-pos + (cond ((char=? c #\|) (list up down)) + ((char=? c #\-) (list left right)) + ((char=? c #\F) (list right down)) + ((char=? c #\L) (list up right)) + ((char=? c #\7) (list left down)) + ((char=? c #\J) (list up left)))) + (let loop ((cur possible-pos)) + (if (not (equal? (car cur) recent)) + (car cur) + (loop (cdr cur))))) + +(define (simulate) + (let loop ((i 0) (cur first-pos) (recent start)) + (if (equal? cur start) + i + (let () + (define next-loc (next cur recent)) + (loop (+ i 1) next-loc cur))))) + +(define loop-length (simulate)) + +(if (= 0 (modulo loop-length 2)) + (/ loop-length 2) + (+ 1 (quotient loop-length 2))) diff --git a/10/2.rkt b/10/2.rkt new file mode 100644 index 0000000..0d9c5a6 --- /dev/null +++ b/10/2.rkt @@ -0,0 +1,112 @@ +#lang racket + +(require "../lib/utils.rkt") + +(define lines + (call-with-input-file "input" + (λ (fp) + (get-lines fp)))) + +(define diagram (list->vector lines)) +(define height (vector-length diagram)) +(define width (string-length (vector-ref diagram 0))) +(define (char-at x y) + (string-ref (vector-ref diagram y) x)) + +(define (find-start) + (let loop ((x 0) (y 0)) + (if (>= y height) + #f + (if (>= x width) + (loop 0 (+ y 1)) + (if (char=? #\S (char-at x y)) + (cons x y) + (loop (+ x 1) y)))))) + +(define start (find-start)) + +(define (valid-pos? pos) + (define x (car pos)) + (define y (cdr pos)) + (and (and (>= x 0) (< x width)) + (and (>= y 0) (< y height)))) + +(define first-pos + (let () + (define up (cons (car start) (- (cdr start) 1))) + (define down (cons (car start) (+ (cdr start) 1))) + (define left (cons (- (car start) 1) (cdr start))) + (define right (cons (+ (car start) 1) (cdr start))) + (cond ((and (valid-pos? up) + (member (char-at (car up) (cdr up)) (list #\| #\F #\7))) + up) + ((and (valid-pos? down) + (member (char-at (car down) (cdr down)) (list #\| #\L #\J ))) + down) + ((and (valid-pos? left) + (member (char-at (car left) (cdr left)) (list #\- #\F #\L ))) + left) + ((and (valid-pos? right) + (member (char-at (car right) (cdr right)) (list #\- #\7 #\J))) + right)))) + +(define (next cur recent) + (define up (cons (car cur) (- (cdr cur) 1))) + (define down (cons (car cur) (+ (cdr cur) 1))) + (define left (cons (- (car cur) 1) (cdr cur))) + (define right (cons (+ (car cur) 1) (cdr cur))) + (define c (char-at (car cur) (cdr cur))) + (define possible-pos + (cond ((char=? c #\|) (list up down)) + ((char=? c #\-) (list left right)) + ((char=? c #\F) (list right down)) + ((char=? c #\L) (list up right)) + ((char=? c #\7) (list left down)) + ((char=? c #\J) (list up left)))) + (let loop ((cur possible-pos)) + (if (not (equal? (car cur) recent)) + (car cur) + (loop (cdr cur))))) + +(define pipes (make-hash)) + +(define (simulate) + (let loop ((i 0) (cur first-pos) (recent start)) + (hash-set! pipes cur '()) + (if (equal? cur start) + i + (let () + (define next-loc (next cur recent)) + (loop (+ i 1) next-loc cur))))) + +(define (mark-junk) + (let loop ((x 0) (y 0)) + (if (>= y height) + (void) + (if (>= x width) + (loop 0 (+ y 1)) + (let () + (when (and (not (hash-has-key? pipes (cons x y))) + (not (char=? #\. (char-at x y)))) + (string-set! (vector-ref diagram y) x #\.)) + (loop (+ 1 x) y)))))) + +(let () + (simulate) + (mark-junk) + (void)) + +(define (ray-cast-find s) + (let loop ((i 0) (flag #f) (ret 0)) + (if (>= i width) + ret + (let () + (define char (string-ref s i)) + (if (and flag (char=? char #\.)) + (loop (+ 1 i) flag (+ 1 ret)) + (if (member char (list #\| #\F #\7)) + (loop (+ 1 i) (not flag) ret) + (loop (+ 1 i) flag ret))))))) + +(apply + (map ray-cast-find (vector->list diagram))) + |