(2022>6)+solution for problem 6

2022/puzzle-6.lisp

@@ -0,0 +1,47 @@
+(defvar input (with-input-from-string (s (uiop:read-file-string "2022/6-input"))
+                (read-line s nil)))
+
+(defun is-unique (lst)
+  (or (null lst)
+     (and (not (member (car lst) (cdr lst)))
+        (is-unique (cdr lst)))))
+
+(defun string-to-list (str)
+  (loop for char across str collect char))
+
+(defun first-round (input)
+  (defun calculate-position (nth)
+    "Calculate the actual position of the nth item."
+    (if nth
+        (+ nth 4)
+        nil))
+
+  (let* ((char-list (string-to-list input))
+         (unique-check (mapcar (lambda (x y z w) (is-unique (list x y z w))) char-list (cdr char-list) (cdr (cdr char-list)) (cdr (cdr (cdr char-list))))))
+    (calculate-position (position t unique-check))))
+
+(format t "First round: ~a~%" (first-round input))
+
+(defun successive-by (lst n)
+  "Returns consecutive subsequences of size N in LST."
+  (loop
+    for item in lst
+    for i from 0
+    collect
+    (if (> (+ n i) (length lst))
+        nil
+        (subseq lst i (+ n i)))))
+
+(defun second-round (input)
+  (defun calculate-position (nth)
+    "Calculate the actual position of the nth item."
+    (if nth
+        (+ nth 14)
+        nil))
+
+
+  (let* ((char-list (string-to-list input))
+         (unique-check (mapcar #'is-unique (successive-by char-list 14))))
+    (calculate-position (position t unique-check))))
+
+(format t "Second round: ~a~%" (second-round input))