diff options
Diffstat (limited to '2022/Day09/part-one.cl')
| -rw-r--r-- | 2022/Day09/part-one.cl | 29 |
1 files changed, 13 insertions, 16 deletions
diff --git a/2022/Day09/part-one.cl b/2022/Day09/part-one.cl index 9e44aa0..f76fa8d 100644 --- a/2022/Day09/part-one.cl +++ b/2022/Day09/part-one.cl @@ -7,13 +7,10 @@ (ask-for-stream (prog-input) (let ((rhead '(0 . 0)) (rtail '(0 . 0)) (visited '((0 . 0))) (movec '())) - (flet ((p-longer-than-sqrt2 (c) - "If c is outside the 3x3 square" + (flet ((norm>sqrt2p (c) ; If c's eucledian length is less than sqrt(2). In other words, if c is outside the 3x3 square. + "Optimized version of (> (norm p) (sqrt 2))" (or (> (abs (car c)) 1) (> (abs (cdr c)) 1))) - (movement-vec (c1 c2) - (cons (- (car c2) (car c1)) (- (cdr c2) (cdr c1)))) - (dir-to-pair (direction) (cond ((char= direction #\R) '( 1 . 0)) ((char= direction #\L) '(-1 . 0)) @@ -21,17 +18,17 @@ ((char= direction #\D) '( 0 . -1))))) (doread-lines (inpt :read-line-options (prog-input NIL)) - (pair+= rhead (*pair (digit-char-p (char inpt 2)) - (dir-to-pair (char inpt 0)))) + (loop for i from 1 to (parse-integer inpt :start 2) - (setf movec (movement-vec rtail rhead)) + do + (pair+= rhead (dir-to-pair (char inpt 0))) + (setf movec (pair- rhead rtail)) - (if (p-longer-than-sqrt2 movec) - (progn (setf movec (pair-round (dist-resize-by movec -1))) ; We dont want to move tail on the head, but behind it - (pair+= rtail movec) + if (norm>sqrt2p movec) + do + ;; dist-resize so we don't put the knot on top of the head, but behind it + (pair+= rtail (pair-round (dist-resize-by movec -1))) + (if (not (member-if (lambda (x) (pair= x rtail)) visited)) + (push rtail visited)))) - (loop for intermvec = movec then (pair-round (dist-resize-by intermvec -1)) - until (pair= intermvec '(0 . 0)) - if (not (member (pair- rtail intermvec) visited)) - do (push (pair- rtail intermvec) visited))))) - (print visited)))) + (print (length visited))))) |