2024/02-1

2024/day-02/stage-1.lisp

@@ -0,0 +1,24 @@
+
+(asdf:load-system "cl-strings")
+
+(require :cl-strings)
+
+(defvar *input*
+  (mapcar (lambda (line)
+            (mapcar (lambda (column) (parse-integer column))
+                    (cl-strings:split line " ")))
+          (uiop:with-safe-io-syntax ()
+            (uiop:read-file-lines "input.txt"))))
+
+(defun gradual-diff-p (record)
+  (cond
+    ((null (cdr record)) t)
+    ((not (< 0 (abs (- (car record) (cadr record))) 4)) nil)
+    (t (gradual-diff-p (cdr record)))))
+
+(defun safep (record)
+  (and (or (apply #'< record)
+           (apply #'> record))
+       (gradual-diff-p record)))
+
+(length (delete nil (mapcar #'safep *input*)))