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(define-module (day10)
#:use-module (ice-9 rdelim)
#:use-module (srfi srfi-1))
(define (read-input port)
(define (iter acc)
(define line (read-line port))
(if (or (eof-object? line) (string= "" line))
(list->typed-array 'u8 2 (reverse acc))
(iter (cons (map
(lambda (c) (- (char->integer c) (char->integer #\0)))
(string->list line))
acc))))
(iter '()))
(define (dp! inp mp num join cellinit)
(define-values (m n) (apply values (array-dimensions inp)))
(unless (negative? num)
(let iter-row ((i 0))
(unless (= i m)
(let iter-cell ((j 0))
(unless (= j n)
(when (= num (array-ref inp i j))
(array-set!
mp
(fold (lambda (di dj acc)
(if (and (array-in-bounds? inp (+ i di) (+ j dj))
(= (+ 1 num) (array-ref inp (+ i di) (+ j dj))))
(join
acc (array-ref mp (+ i di) (+ j dj)))
acc))
cellinit
'(1 -1 0 0) '(0 0 1 -1))
i j))
(iter-cell (+ j 1))))
(iter-row (+ i 1))))
(dp! inp mp (- num 1) join cellinit)))
(define (doit port score join cellinit 9init)
(define inp (read-input port))
(define-values (m n) (apply values (array-dimensions inp)))
(define mp (make-array 0 m n))
(define idx 0)
(array-map! mp (lambda (s) (if (= s 9) (9init) cellinit)) inp)
(dp! inp mp 8 join cellinit)
;(display mp)
(let iter-row ((i 0) (acc 0))
(if (= i m)
acc
(iter-row (+ i 1)
(let iter-cell ((j 0) (acc acc))
(if (= j n)
acc
(iter-cell (+ j 1)
(+ acc (if (= (array-ref inp i j) 0)
(score (array-ref mp i j))
0)))))))))
(define (part1 port)
(define idx 0)
(doit port length (lambda (a b) (lset-union = a b))
'()
(lambda () (set! idx (+ idx 1)) (list idx))))
(define (part2 port)
(doit port values + 0 (lambda () 1)))
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