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Day 09: Use vectors instead of lists.

This commit is contained in:
Jonathan Chan 2021-12-09 00:25:27 -08:00
parent 59b8087029
commit efd3cc9059
1 changed files with 15 additions and 17 deletions
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32
src/09.rkt
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@ -4,18 +4,18 @@
"../lib.rkt") "../lib.rkt")
(define input (define input
(~>> (problem-input 9) (for/vector ([row (problem-input 9)])
(map string->list) (for/vector ([col (string->list row)])
(map #{map char->number %}))) (char->number col))))
(define rows (length input)) (define rows (vector-length input))
(define cols (length (first input))) (define cols (vector-length (vector-ref input 0)))
(define (grid-ref grid row col [default +inf.0]) (define (grid-ref grid row col [default +inf.0])
(if (or (< row 0) (>= row rows) (if (or (< row 0) (>= row rows)
(< col 0) (>= col cols)) (< col 0) (>= col cols))
default default
(list-ref (list-ref grid row) col))) (vector-ref (vector-ref grid row) col)))
(define (neighbours row col) (define (neighbours row col)
(list (cons (sub1 row) col) (list (cons (sub1 row) col)
@ -44,16 +44,14 @@
(set-add seen loc)))))) (set-add seen loc))))))
(define-values (part1 part2) (define-values (part1 part2)
(for/fold ([risk 0] (for*/fold ([risk 0]
[basins '()] [basins '()]
#:result (values risk (apply * (take (sort basins >) 3)))) #:result (values risk (apply * (take (sort basins >) 3))))
([row (range rows)]) ([row (range rows)]
(for/fold ([risk risk] [col (range cols)])
[basins basins]) (if (low? row col)
([col (range cols)]) (values (+ (add1 (grid-ref input row col)) risk)
(if (low? row col) (cons (basin row col) basins))
(values (+ (add1 (grid-ref input row col)) risk) (values risk basins))))
(cons (basin row col) basins))
(values risk basins)))))
(show-solution part1 part2) (show-solution part1 part2)