32 lines
863 B
Racket
32 lines
863 B
Racket
#lang racket
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(require "../lib.rkt")
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(define input (map string->number (problem-input 9)))
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(define input* (list->vector input))
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(define (pair-sum start end)
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(for*/or ([i (range start end)]
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[j (range start end)])
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(= (vector-ref input* end)
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(+ (vector-ref input* i)
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(vector-ref input* j)))))
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(define part1
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(let loop ([start 0] [end 25])
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(if (pair-sum start end)
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(loop (add1 start) (add1 end))
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(vector-ref input* end))))
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(define part2
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(let loop ([start 0] [end 0] [sum 0])
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(cond
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[(< sum part1)
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(loop start (add1 end) (+ sum (vector-ref input* end)))]
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[(> sum part1)
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(loop (add1 start) end (- sum (vector-ref input* start)))]
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[else (let ([contig (drop (take input end) start)])
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(+ (apply min contig) (apply max contig)))])))
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(show-solution part1 part2)
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