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#lang racket
(struct monkey
(items operation divisible if-true if-false inspections)
#:mutable #:transparent)
(define (parse desc)
(let* ([lines (string-split desc "\n")]
[items (map string->number
(string-split (second (string-split (second lines) ": "))
", "))]
[operation
(match (string-split (second (string-split (third lines) "old ")) " ")
[(list "*" "old") (lambda (old) (* old old))]
[(list "*" n) (lambda (old) (* old (string->number n)))]
[(list "+" n) (lambda (old) (+ old (string->number n)))])]
[test (string->number (last (string-split (fourth lines) " ")))]
[if-true (string->number (last (string-split (fifth lines) " ")))]
[if-false (string->number (last (string-split (sixth lines) " ")))]
)
(monkey items operation test if-true if-false 0)))
(define monkeys
(for/vector ([para (string-split (file->string "day11") "\n\n")])
(parse para)))
(define q (for/product ([m monkeys]) (monkey-divisible m)))
(define (step monkeys part)
(for ([m monkeys])
(for ([item (monkey-items m)])
(let* ([worry ((monkey-operation m) item)]
[worry-bored (if (= part 1)
(quotient worry 3)
(remainder worry q))]
[to (if (zero? (remainder worry-bored (monkey-divisible m)))
(monkey-if-true m)
(monkey-if-false m))]
[mto (vector-ref monkeys to)])
(set-monkey-inspections! m (+ 1 (monkey-inspections m)))
(set-monkey-items! mto
(append (monkey-items mto) (list worry-bored))))
(set-monkey-items! m '()))))
(for ([i (in-inclusive-range 1 20)])
(step monkeys 1))
(apply * (take (sort (for/list ([m monkeys]) (monkey-inspections m)) >) 2))
;; 54253
(set! monkeys
(for/vector ([para (string-split (file->string "day11") "\n\n")])
(parse para)))
(for ([i (in-inclusive-range 1 10000)])
(step monkeys 2))
(apply * (take (sort (for/list ([m monkeys]) (monkey-inspections m)) >) 2))
;; 13119526120
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