diff options
Diffstat (limited to '2024/11/puzzles.lisp')
| -rw-r--r-- | 2024/11/puzzles.lisp | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/2024/11/puzzles.lisp b/2024/11/puzzles.lisp new file mode 100644 index 0000000..9c3c73b --- /dev/null +++ b/2024/11/puzzles.lisp @@ -0,0 +1,46 @@ +#!/usr/bin/sbcl --script + +(defparameter *memo* (make-hash-table :test 'equal)) + +(defun main (filename blink-count) + (let ((stones (read-stones filename))) + (loop for stone in stones + 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) + (or (gethash (cons stone blink-count) *memo*) + (setf (gethash (cons stone blink-count) *memo*) + (cond ((= (decf blink-count) -1) + 1) + ((= stone 0) + (count-stones 1 blink-count)) + ((evenp (integer-digit-count stone)) + (let ((hi-lo (integer-split stone))) + (+ (count-stones (car hi-lo) blink-count) + (count-stones (cdr hi-lo) blink-count)))) + (:else + (count-stones (* 2024 stone) blink-count)))))) + +(defun integer-digit-count (x) + (loop with n = 0 + while (/= x 0) + do (progn (incf n) (setq x (floor x 10))) + finally (return n))) + +(defun integer-split (x) + (let* ((n (floor (integer-digit-count x) 2)) + (m (expt 10 n))) + (cons (floor x m) + (mod x m)))) + +;; START PART 1 +(format t "~d~%" (main "input" 25)) +;; END PART 1 START PART 2 +(format t "~d~%" (main "input" 75)) +;; END PART 2
\ No newline at end of file |