Add an Emacs Lisp solution

1 files changed, 21 insertions, 0 deletions

diff --git a/2024/01/puzzle-1.el b/2024/01/puzzle-1.el
new file mode 100644
index 0000000..cd8853e
--- /dev/null
+++ b/2024/01/puzzle-1.el
@@ -0,0 +1,21 @@
+(defun solve (input-file)
+  (let* ((nums (with-temp-buffer
+                 (insert-file-contents-literally input-file)
+                 (goto-char (point-min))
+                 (save-excursion
+                   (insert ?\[)
+                   (goto-char (point-max))
+                   (insert ?\]))
+                 (read (current-buffer))))
+         (num-count (length nums)))
+    (cl-loop for i from 0 below num-count
+             if (cl-evenp i)
+               collect (aref nums i) into xs
+             else
+               collect (aref nums i) into ys
+             finally return (thread-last
+                              (seq-mapn #'- (sort xs) (sort ys))
+                              (mapcar #'abs)
+                              (apply #'+)))))
+
+(message "%d" (solve "input"))
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