30 lines
1 KiB
Scheme
30 lines
1 KiB
Scheme
(import (scheme base)
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(scheme char)
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(scheme file)
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(scheme process-context)
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(scheme write))
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(define (max-joltage line batteries)
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(let ((lst (map digit-value (string->list line))))
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(let loop ((req-tail-length (- batteries 1))
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(lst lst)
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(sum 0))
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(if (negative? req-tail-length)
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sum
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;; this is O^one million at least
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(let ((m (memq (apply max (reverse (list-tail (reverse lst) req-tail-length))) lst)))
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(loop (- req-tail-length 1) (cdr m) (+ (* sum 10) (car m))))))))
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(define (part file batteries)
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(with-input-from-file file
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(lambda ()
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(let loop ((line (read-line))
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(sum 0))
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(if (eof-object? line)
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(begin
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(display (number->string sum))
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(newline))
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(loop (read-line) (+ sum (max-joltage line batteries))))))))
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(for-each (lambda (file) (part file 2)) (cdr (command-line)))
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(for-each (lambda (file) (part file 12)) (cdr (command-line)))
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