From 983c4a10344dc0416d9e87d955eaab56c5db9292 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 11 Dec 2024 11:07:10 +0100 Subject: Add 2024 day 11 part 1 solution --- 2024/11/input | 1 + 2024/11/puzzle-1.lisp | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 52 insertions(+) create mode 100644 2024/11/input create mode 100755 2024/11/puzzle-1.lisp (limited to '2024') diff --git a/2024/11/input b/2024/11/input new file mode 100644 index 0000000..cceb3f6 --- /dev/null +++ b/2024/11/input @@ -0,0 +1 @@ +112 1110 163902 0 7656027 83039 9 74 \ No newline at end of file diff --git a/2024/11/puzzle-1.lisp b/2024/11/puzzle-1.lisp new file mode 100755 index 0000000..3fc7df7 --- /dev/null +++ b/2024/11/puzzle-1.lisp @@ -0,0 +1,51 @@ +#!/usr/bin/sbcl --script + +(defparameter *numbers* + '()) + +(defun main (filename) + (setq *numbers* (read-stones filename)) + (loop repeat 25 + do (blink) + finally (return (length *numbers*)))) + +(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 blink () + (setq *numbers* + (loop for number in *numbers* + for after-blink = (stone-change-or-split number) + if (listp after-blink) + append after-blink + else + collect after-blink + finally (setq *numbers* after-blink)))) + +(defun stone-change-or-split (number) + (cond ((= number 0) + 1) + ((evenp (digit-count number)) + (number-split number)) + (:else + (* 2024 number)))) + +(defun digit-count (number) + (loop with x = 0 + while (/= number 0) + do (progn + (incf x) + (setq number (floor number 10))) + finally (return x))) + +(defun number-split (number) + (let* ((length (digit-count number)) + (string (write-to-string number)) + (half (/ length 2))) + (list (parse-integer (subseq string 0 half)) + (parse-integer (subseq string half (length string)))))) + +(format t "~d~%" (main "input")) \ No newline at end of file -- cgit v1.2.3