aboutsummaryrefslogtreecommitdiff
path: root/puzzle-3.lisp
diff options
context:
space:
mode:
authorAryadev Chavali <aryadev@aryadevchavali.com>2023-06-26 08:33:59 +0100
committerAryadev Chavali <aryadev@aryadevchavali.com>2023-06-26 08:33:59 +0100
commit29cacf2394a6d64f1ab3d5ba13a35f3beb08c3c7 (patch)
tree36b2ff2c409b9956e83481589fba9f38326eae08 /puzzle-3.lisp
parentf8a0d0f1acc50711e470999434f7f8f504188b2e (diff)
downloadadvent-of-code-29cacf2394a6d64f1ab3d5ba13a35f3beb08c3c7.tar.gz
advent-of-code-29cacf2394a6d64f1ab3d5ba13a35f3beb08c3c7.tar.bz2
advent-of-code-29cacf2394a6d64f1ab3d5ba13a35f3beb08c3c7.zip
(3|4)+lisp files for puzzles 3 and 4
Diffstat (limited to 'puzzle-3.lisp')
-rw-r--r--puzzle-3.lisp67
1 files changed, 67 insertions, 0 deletions
diff --git a/puzzle-3.lisp b/puzzle-3.lisp
new file mode 100644
index 0000000..dcb8bc3
--- /dev/null
+++ b/puzzle-3.lisp
@@ -0,0 +1,67 @@
+(defvar input (uiop:read-file-string "puzzle-3-input.txt"))
+
+(defun split-string-in-two (s)
+ (let ((len (length s)))
+ (list (subseq s 0 (/ len 2)) (subseq s (/ len 2)))))
+
+(defvar inputs (with-input-from-string (s input)
+ (loop
+ for line = (read-line s nil)
+ until (null line)
+ collect (split-string-in-two line))))
+
+(defun string-to-clist (str)
+ (loop for char across str collect char))
+
+(defun common-types (s1 s2)
+ (car (intersection
+ (string-to-clist s1)
+ (string-to-clist s2))))
+
+(defvar shared (mapcar (lambda (x)
+ (destructuring-bind (s1 s2) x
+ (common-types s1 s2)))
+ inputs))
+
+(defun priority-map (c)
+ (if (upper-case-p c)
+ (+ 27 (- (char-code c) (char-code #\A)))
+ (+ 1 (- (char-code c) (char-code #\a)))))
+
+(defvar round-1-answer (reduce #'+ (mapcar #'priority-map shared)))
+
+;; Round 2
+
+;; Simple recursive algorithm which produces consecutive groups of 3 elements
+(defun group-by-3 (lst)
+ (if (null lst)
+ nil
+ (cons
+ (list (car lst) (car (cdr lst)) (car (cdr (cdr lst))))
+ (group-by-3 (cdr (cdr (cdr lst)))))))
+
+;; Note the use of group-by-3 here
+(defvar inputs (group-by-3
+ (with-input-from-string (s input)
+ (loop
+ for line = (read-line s nil)
+ until (null line)
+ collect line))))
+
+;; Extend intersection to three
+(defun common-types-3 (s1 s2 s3)
+ (car
+ (intersection
+ (string-to-clist s1)
+ (intersection
+ (string-to-clist s2)
+ (string-to-clist s3)))))
+
+;; Extend the destructuring bind and use of common-types-3
+(defvar shared (mapcar (lambda (x)
+ (destructuring-bind (s1 s2 s3) x
+ (common-types-3 s1 s2 s3)))
+ inputs))
+
+;; Same as before
+(defvar round-2-answer (reduce #'+ (mapcar #'priority-map shared)))