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42 lines
983 B
Racket
42 lines
983 B
Racket
#lang racket
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(define crabs
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(map string->number
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(string-split
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(first
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(file->lines "day7.txt")) ",")))
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(define (distances crabs position)
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(foldl (λ (x acc) (+ acc (abs (- position x)))) 0 crabs))
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(define (min-distance crab)
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(let* ([rng (range (apply min crabs) (apply max crabs))]
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[ds (map (λ (d) (distances crabs d)) rng)])
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(apply min ds)))
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(define part1 (min-distance crabs))
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part1
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; part 2
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(define (big-distance d)
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(if (= d 0) 0 (+ d (big-distance (sub1 d)))))
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(define (memo1 fn arg1)
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(let* ([ht (make-hash)])
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(hash-ref! ht (list fn arg1) (fn arg1))))
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(define bd2-memo (λ (x) (memo1 big-distance x)))
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(define (distances2 crabs position)
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(foldl (λ (x acc) (+ acc (bd2-memo (abs (- position x))))) 0 crabs))
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(define (min-distance2 crab)
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(let* ([rng (range (apply min crabs) (apply max crabs))]
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[ds (map (λ (d) (distances2 crabs d)) rng)])
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(apply min ds)))
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(define part2 (min-distance2 crabs))
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part2 |