diff options
| -rw-r--r-- | 13/1.rkt | 40 | ||||
| -rw-r--r-- | lib/utils.rkt | 14 |
2 files changed, 53 insertions, 1 deletions
diff --git a/13/1.rkt b/13/1.rkt new file mode 100644 index 0000000..21c29c3 --- /dev/null +++ b/13/1.rkt @@ -0,0 +1,40 @@ +#lang racket + +(require "../lib/utils.rkt") + +(define lines + (call-with-input-file "input" + (λ (fp) (get-lines fp)))) + +(define patterns (split-list-by "" lines)) + +(define (find-reflection lines) + (define lines-vec (list->vector lines)) + (define len (vector-length lines-vec)) + (define (find-first) + (let loop ((i 0) (ret '())) + (if (>= i (- len 1)) + (reverse ret) + (if (string=? (vector-ref lines-vec i) + (vector-ref lines-vec (+ i 1))) + (loop (+ 1 i) (cons i ret)) + (loop (+ 1 i) ret))))) + (define (count start) + (let loop ((cnt 1) (i start)) + (if (or (< i 0) + (>= (+ start cnt) len)) + (+ start 1) + (if (string=? (vector-ref lines-vec i) + (vector-ref lines-vec (+ start cnt))) + (loop (+ 1 cnt) (- i 1)) + 0)))) + (define start (find-first)) + (if (null? start) + 0 + (apply max (map count start)))) + +(define (score pattern) + (+ (* 100 (find-reflection pattern)) + (find-reflection (transpose-list pattern)))) + +(apply + (map score patterns)) diff --git a/lib/utils.rkt b/lib/utils.rkt index 2371583..974e453 100644 --- a/lib/utils.rkt +++ b/lib/utils.rkt @@ -3,7 +3,8 @@ (provide get-lines enumerate repeat - split-list-by) + split-list-by + transpose-list) (define (repeat n e) (let loop ((i 0) (ret '())) @@ -41,3 +42,14 @@ (if (cmp e (car lst)) (loop (cons (reverse cur) ret) '() (cdr lst)) (loop ret (cons (car lst) cur) (cdr lst)))))) + +(define (transpose-list lines) + (define width (string-length (car lines))) + (define new-lines (make-vector width)) + (let loop ((i 0)) + (if (>= i width) + (vector->list new-lines) + (let () + (define char-list (map (λ (l) (string-ref l i)) lines)) + (vector-set! new-lines i (list->string char-list)) + (loop (+ i 1))))))
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