Add 2024 day 10 solutions

1 files changed, 42 insertions, 0 deletions

diff --git a/2024/10/puzzles.lisp b/2024/10/puzzles.lisp
new file mode 100644
index 0000000..696bb25
--- /dev/null
+++ b/2024/10/puzzles.lisp
@@ -0,0 +1,42 @@
+#!/usr/bin/sbcl --script
+
+
+(defun main (filename)
+  (let ((lines (read-file-to-lines filename)))
+    (loop with dimensions = (array-dimensions lines)
+          for i from 0 below (first dimensions)
+          summing (loop for j from 0 below (second dimensions)
+                        when (char= #\0 (aref lines i j))
+                        summing (score-for-trail-head lines i j)))))
+
+(defun read-file-to-lines (filename)
+  (with-open-file (stream filename)
+    (let ((lines (loop for line = (read-line stream nil)
+                       while line
+                       collect (coerce line 'array))))
+      (make-array (list (length lines)
+                        (length (first lines)))
+                  :initial-contents lines))))
+
+(defun score-for-trail-head (lines i j)
+  (let* ((positions (positions-of-nines lines i j))
+         ;; START PART 1
+         (positions (remove-duplicates positions :test 'equal))
+         ;; END PART 1
+         )
+    (length positions)))
+
+(defun positions-of-nines (lines i j)
+  (let ((char (aref lines i j)))
+    (if (char= #\9 char)
+        (list (cons i j))
+        (loop with needs = (code-char (1+ (char-code char)))
+              with dimensions = (array-dimensions lines)
+              for (i . j) in (list (cons (1- i) j) (cons i (1- j))
+                                   (cons (1+ i) j) (cons i (1+ j)))
+              when (and (< -1 i (first dimensions))
+                        (< -1 j (second dimensions))
+                        (char= (aref lines i j) needs))
+              append (positions-of-nines lines i j)))))
+
+(format t "~a~%" (main "input"))
\ No newline at end of file