28 lines
765 B
Racket
28 lines
765 B
Racket
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#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 (pair-sum lst target)
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(for*/or ([i lst]
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[j lst])
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(= (+ i j) target)))
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(define part1
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(let loop ([current (take input 25)] [next (list-ref input 25)] [remain (drop input 26)])
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(if (pair-sum current next)
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(loop (snoc (rest current) next) (first remain) (rest remain))
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next)))
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(define part2
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(let loop ([current '()] [remain input] [sum 0])
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(cond
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[(< sum part1)
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(loop (snoc current (first remain)) (rest remain) (+ sum (first remain)))]
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[(> sum part1)
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(loop (rest current) remain (- sum (first current)))]
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[else (+ (apply min current) (apply max current))])))
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(show-solution part1 part2)
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