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- (import (chicken io))
- (import (chicken string))
- (import srfi-69)
- (import srfi-1)
- (define (read-input)
- (with-input-from-file "input"
- (lambda ()
- (define part1
- (let loop ((ret '()))
- (let ((line (read-line)))
- (if (= 0 (string-length line))
- (reverse ret)
- (loop (cons line ret))))))
- (define part2
- (let loop ((ret '()))
- (let ((line (read-line)))
- (if (eof-object? line)
- (reverse ret)
- (loop (cons line ret))))))
- (values part1 part2))))
- (define-values (part1 part2) (read-input))
- (set! part1 (map (lambda (x) (string-split x "|")) part1))
- (set! part1 (map (lambda (x) (map string->number x)) part1))
- (define rules (make-hash-table))
- (map (lambda (x)
- (hash-table-set! rules x #t) '())
- part1)
- (define updates (map (lambda (x) (string-split x ",")) part2))
- (set! updates (map (lambda (x) (map string->number x)) updates))
- (define (check-rules x lst)
- (if (null? lst)
- #t
- (and (not (hash-table-ref/default rules (list (car lst) x) #f))
- (check-rules x (cdr lst)))))
- (define (check-update update)
- (if (null? update)
- #t
- (and (check-rules (car update) (cdr update))
- (check-update (cdr update)))))
- (define (median lst)
- (list-ref lst (quotient (length lst) 2)))
- (display (apply + (map median (filter check-update updates))))
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