diff options
Diffstat (limited to 'AoC2022/12/solver.lisp')
| -rw-r--r-- | AoC2022/12/solver.lisp | 32 |
1 files changed, 17 insertions, 15 deletions
diff --git a/AoC2022/12/solver.lisp b/AoC2022/12/solver.lisp index b2a0752..e0320c3 100644 --- a/AoC2022/12/solver.lisp +++ b/AoC2022/12/solver.lisp @@ -17,28 +17,28 @@ (when (< 0 y height) (- pos width))) ;; up move :test #'eq)))) -(defun elevations (data) - (map 'vector (lambda (chr) - (case chr - (#\S 0) - (#\E 27) - (t (- (char-code chr) 96)))) - data)) +(defun elevation (chr) + (case chr + (#\S 0) + (#\E 27) + (t (- (char-code chr) 96)))) (defun land (input-file) (let ((data (uiop:read-file-lines input-file))) - (make-land :elevation (elevations (apply #'concatenate 'string data)) + (make-land :elevation (map 'vector #'elevation (apply #'concatenate 'string data)) :neighbors (possible-directions (length (car data)) (length data))))) +(defun appropriate (place elevation land paths) + (and (not (gethash place paths)) ;; not visited + (>= elevation (aref (land-elevation land) place)))) + (defun next-steps (place land paths) (let ((elevation (aref (land-elevation land) place))) (unless (= 27 elevation) - (mapcan (lambda (option) - (when (and (not (gethash option paths)) - (>= (1+ elevation) (aref (land-elevation land) option))) - (setf (gethash option paths) (cons option (gethash place paths))) - (list option))) - (funcall (land-neighbors land) place))))) + (loop :for option :in (funcall (land-neighbors land) place) + :when (appropriate option (1+ elevation) land paths) + :do (setf (gethash option paths) (cons option (gethash place paths))) + :and collect option)))) (defun shortest-path (starts land paths) (let ((next (mapcan (lambda (place) (next-steps place land paths)) starts))) @@ -51,7 +51,9 @@ (finish (position 27 (land-elevation land) :test #'eq)) (starts (loop for i from 0 for el across (land-elevation land) - when (funcall start-p el) collect (progn (setf (gethash i paths) (list i)) i)))) + when (funcall start-p el) + do (setf (gethash i paths) (list i)) + and collect i))) (shortest-path starts land paths) (1- (length (gethash finish paths))))) |