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authorH.J <thechairman@thechairman.info>2024-10-09 11:36:55 -0400
committerH.J <thechairman@thechairman.info>2024-10-09 11:36:55 -0400
commit8777ff071f7bb37631baa7b6717ad29961e50911 (patch)
tree6d59c4ed58e454b960339c3d1151f0a879e8d7cb /racket/aoc2020/day-03
parent6156a9ef7be4012063a042aafb4e9b0d7eadde8e (diff)
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-rw-r--r--racket/aoc2020/day-03/day-03.rkt16
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diff --git a/racket/aoc2020/day-03/day-03.rkt b/racket/aoc2020/day-03/day-03.rkt
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+#lang racket
+(require "../../jj-aoc.rkt"
+ threading)
+
+(define (check-for-trees run rise)
+ (for*/sum ([(row i) (in-indexed (port->lines (open-day 3 2020)))]
+ #:when (= 0 (modulo i rise))
+ [possible-tree (in-value (sequence-ref (in-cycle row) (* (/ run rise) i)))]
+ #:when (and (char=? possible-tree #\#)))
+ 1))
+
+;; part 1
+(check-for-trees 3 1)
+
+;; part 2
+(~>> '((1 1) (3 1) (5 1) (7 1) (1 2)) (map (curry apply check-for-trees)) (apply *))