diff options
| -rw-r--r-- | 14/1.rkt | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/14/1.rkt b/14/1.rkt new file mode 100644 index 0000000..79dcefc --- /dev/null +++ b/14/1.rkt @@ -0,0 +1,63 @@ +#lang racket + +(require "../lib/utils.rkt") + +(define lines + (call-with-input-file "input" + (λ (fp) (get-lines fp)))) + +(define mat (list->vector lines)) + +(define (char-at x y) + (string-ref (vector-ref mat y) x)) + +(define (set-mat! x y c) + (string-set! (vector-ref mat y) x c)) + +(define (move-stone x1 y1 x2 y2) + (define t (char-at x1 y1)) + (set-mat! x1 y1 (char-at x2 y2)) + (set-mat! x2 y2 t)) + +(define (find-new-pos x y) + (let loop ((new-y y)) + (if (or (= new-y 0) + (not (char=? #\. (char-at x (- new-y 1))))) + new-y + (loop (- new-y 1))))) + +(define height (vector-length mat)) +(define width (string-length (vector-ref mat 0))) + +(define (tilt) + (let loop ((y 0)) + (if (>= y height) + (void) + (let () + (let loop1 ((x 0)) + (if (>= x width) + (void) + (let () + (define c (char-at x y)) + (if (char=? #\O c) + (let () + (define new-y (find-new-pos x y)) + (move-stone x y x new-y) + (loop1 (+ 1 x))) + (loop1 (+ 1 x)))))) + (loop (+ 1 y)))))) + +(define (count) + (let loop ((x 0) (y 0) (sum 0)) + (if (>= y height) + sum + (if (>= x width) + (loop 0 (+ 1 y) sum) + (let () + (define c (char-at x y)) + (if (char=? c #\O) + (loop (+ 1 x) y (+ sum (- height y))) + (loop (+ 1 x) y sum))))))) + +(tilt) +(count)
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