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adventofcode
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Day 02.

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Jonathan Chan 2021-12-01 21:37:35 -08:00 committed by Jonathan Chan
parent c8166089be
commit 66fb5ddd5b
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input/02.txt Normal file
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src/02.rkt Normal file
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#lang racket
(require "../lib.rkt")
(define input
(for/list ([line (problem-input 2)])
(match (string-split line " ")
[`(,dir ,val) (list (string->symbol dir) (string->number val))])))
(define part1
(let ([horiz (sum (filter-map (match-lambda [`(forward ,n) n] [else #f]) input))]
[ups (sum (filter-map (match-lambda [`(up ,n) n] [else #f]) input))]
[downs (sum (filter-map (match-lambda [`(down ,n) n] [else #f]) input))])
(* horiz (- downs ups))))
(define part2
(for/fold ([aim 0]
[horiz 0]
[depth 0]
#:result (* horiz depth))
([dir-val input])
(match dir-val
[`(forward ,val) (values aim (+ horiz val) (+ depth (* aim val)))]
[`(up ,val) (values (- aim val) horiz depth)]
[`(down ,val) (values (+ aim val) horiz depth)])))
(show-solution part1 part2)