Current Status

As of this post I only did Day 1, 2, and 3. The current day for this is Day 6. I been doing this at my own pace. I feel like I’m getting better with lisp with these puzzles, and I had to look at other people’s solutions to fully understand what the problem was asking for.

Day 3

Day 3 has you finding out how many trees you hit on a toboggan stuck on one path here is the code (defparameter toboggan-vel ‘((1 1) (3 1) (5 1) (7 1) (1 2))) (defun read-file-in (filename) (with-open-file ( in filename :if-does-not-exist nil :external-format ‘(:utf-8 :replacement “?”)) (loop for line = ( read-line in nil nil ) while line collect line))) (defun is-tree? (pos-char) (if (char= pos-char ##) t)) (defun toboggan-y-vel (lines vel) (cond ((eq lines nil) ‘()) ((= vel 0) lines) (t (toboggan-y-vel (cdr lines) (- vel 1))))) (defun check-toboggan-path (lines pos) (cond ((eq lines nil) ‘()) ((not (is-tree? (char (subseq (car lines) pos (+ pos 1)) 0))) (cons #\O (check-toboggan-path (cdr lines) (mod (+ pos toboggan-x-vel) (length (car lines)))))) ((is-tree? (char (subseq (car lines) pos (+ pos 1)) 0)) (cons #\X (check-toboggan-path (cdr lines) (mod (+ pos toboggan-x-vel) (length (car lines)))))) (t ‘()))) (defun check-toboggan-path-2 (lines pos y-vel x-vel) (cond ((eq lines nil) ‘()) ((not (is-tree? (char (subseq (car lines) pos (+ pos 1)) 0))) (cons #\O (check-toboggan-path-2 (toboggan-y-vel lines y-vel) (mod (+ pos x-vel) (length (car lines))) y-vel x-vel))) ((is-tree? (char (subseq (car lines) pos (+ pos 1)) 0)) (cons #\X (check-toboggan-path-2 (toboggan-y-vel lines y-vel) (mod (+ pos x-vel) (length (car lines))) y-vel x-vel))) (t ‘()))) (defun count-tree-hits (path) (loop for item in path when (char= item #\X) sum 1 into total finally (return total))) (defun mul-tree-hit-counts (tree-hit-list) (cond ((eq tree-hit-list nil) 1) (t (* (car tree-hit-list) (mul-tree-hit-counts (cdr tree-hit-list)))))) (defun loop-vel () (loop for item in toboggan-vel collect (count-tree-hits (check-toboggan-path-2 (read-file-in “puz3.in”) 0 (cadr item) (car item)))))