diff options
Diffstat (limited to 'AoC2023/day17/solver.lisp')
| -rw-r--r-- | AoC2023/day17/solver.lisp | 43 |
1 files changed, 27 insertions, 16 deletions
diff --git a/AoC2023/day17/solver.lisp b/AoC2023/day17/solver.lisp index 7001eb8..a3c47f6 100644 --- a/AoC2023/day17/solver.lisp +++ b/AoC2023/day17/solver.lisp @@ -34,19 +34,19 @@ (dw 'up) (lf 'rt))) -(defun next-moves (field tried walker) +(defun next-moves (field tried walker turn-condition) (destructuring-bind (track dir row col) walker (arrows:->> (remove dir '(rt dw lf up) :key #'backtrack) (mapcar (lambda (d) - (unless (and (eq d dir) (<= 2 track)) - (destructuring-bind (ndir . np) (advance row col d) - (when (in-bounds field np) - (let* ((nt (if (eq ndir dir) (1+ track) 0)) - (npath (list* nt ndir np))) - (unless (gethash npath tried) - (setf (gethash npath tried) t) - npath))))))) + (let ((nt (if (eq d dir) (1+ track) 0))) + (when (funcall turn-condition d dir (1+ track)) + (destructuring-bind (ndir . np) (advance row col d) + (when (in-bounds field np) + (let ((npath (list* nt ndir np))) + (unless (gethash npath tried) + (setf (gethash npath tried) t) + npath)))))))) (delete nil)))) (defun finish-p (field step) @@ -58,22 +58,33 @@ (defun vdequeue (q) (cl-heap:pop-heap (slot-value q 'cl-heap:heap))) -(defun walk (options known field) +(defun walk (options known field turn-condition) (loop for (pcost current) = (vdequeue options) while current until (finish-p field current) - do (dolist (next (next-moves field known current)) + do (dolist (next (next-moves field known current turn-condition)) (cl-heap:enqueue options next (+ (apply #'aref field (cddr next)) pcost))) finally (return pcost))) -(defun solver (filename) +(defun part1-turn (d dir track) + (or (not (eq d dir)) (< track 3))) + +(defun part2-turn (d dir track) + (or (and (not (eq d dir)) + (>= track 4)) + (and (eq d dir) + (< track 10)))) + +(defun solver (filename turn-condition) (let* ((field (parse-input filename)) (options (make-instance 'cl-heap:priority-queue)) (known (make-hash-table :test #'equal)) - (w (list -1 'rt 0 0))) + (w (list 10 'rest 0 0))) (cl-heap:enqueue options w 0) - (walk options known field))) + (walk options known field turn-condition))) (fiveam:test solutions - (fiveam:is (= 102 (solver "eg-in"))) - (fiveam:is (= 963 (solver "input")))) + (fiveam:is (= 102 (solver "eg-in" #'part1-turn))) + (fiveam:is (= 963 (solver "input" #'part1-turn))) + (fiveam:is (= 94 (solver "eg-in" #'part2-turn))) + (fiveam:is (= 1178 (solver "input" #'part2-turn)))) |