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#lang racket
(require threading
"../jj-aoc.rkt")
(define data
(for/vector ([l (in-lines (open-day 9))]
#:unless (equal? l ""))
(~>> l
string->list
(map (λ~>> ~a string->number))
list->vector)))
(define max-rows (vector-length data))
(define max-cols (vector-length (vector-ref data 0)))
(define-values (min-rows min-cols) (values 0 0))
(define (vector2d-ref vec coord)
(match-define `(,r ,c) coord)
(~> vec
(vector-ref r)
(vector-ref c)))
(define (adjacent coords)
(match-define `(,r ,c) coords)
`((,(add1 r) ,c)
(,(sub1 r) ,c)
(,r ,(add1 c))
(,r ,(sub1 c))))
(define (valid-coordinate coord)
(match-define `(,r ,c) coord)
(and (>= r min-rows)
(< r max-rows)
(>= c min-cols)
(< c max-cols)))
(define (check-adjacent vec coord)
(define x (vector2d-ref vec coord))
(for*/and ([neighbor (in-list (adjacent coord))]
#:when (valid-coordinate neighbor))
(x . < . (vector2d-ref vec neighbor))))
;; part 1
(for*/sum ([r (in-range min-rows max-rows)]
[c (in-range min-cols max-cols)]
[x (in-value (vector2d-ref data `(,r ,c)))]
#:when (check-adjacent data `(,r ,c)))
(add1 x))
;; part 2
(define visited (make-hash))
(define (flood-fill vec coord)
(if (and (< (vector2d-ref vec coord) 9)
(not (hash-has-key? visited coord)))
((hash-set! visited coord 'visited)
(add1 (for/sum [(neighbor (in-list (adjacent coord)))
#:when (valid-coordinate neighbor)]
(flood-fill vec neighbor))))
0))
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