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#!/usr/bin/sbcl --script
(defparameter *memo* (make-hash-table :test 'equal))
(defun main (filename blink-count)
(loop for stone in (read-stones filename)
sum (count-stones stone blink-count)))
(defun read-stones (filename)
(with-open-file (stream filename)
(let ((contents (make-string (file-length stream))))
(read-sequence contents stream)
(read-from-string (concatenate 'string "(" contents ")")))))
(defun count-stones (stone blink-count)
(let ((stone+blink-count (cons stone blink-count)))
(or (gethash stone+blink-count *memo*)
(setf (gethash stone+blink-count *memo*)
(cond ((minusp (decf blink-count))
1)
((zerop stone)
(count-stones 1 blink-count))
((evenp (integer-digit-count stone))
(multiple-value-bind (hi lo) (integer-split stone)
(+ (count-stones hi blink-count)
(count-stones lo blink-count))))
(:else
(count-stones (* 2024 stone) blink-count)))))))
(defun integer-digit-count (x)
(1+ (truncate (log x 10))))
(defun integer-split (x)
(floor x (expt 10 (floor (integer-digit-count x) 2))))
;; START PART 1
(format t "~d~%" (main "input" 25))
;; END PART 1 START PART 2
(format t "~d~%" (main "input" 75))
;; END PART 2
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