diff options
Diffstat (limited to 'AoC2022/18/solver.lisp')
| -rw-r--r-- | AoC2022/18/solver.lisp | 46 |
1 files changed, 45 insertions, 1 deletions
diff --git a/AoC2022/18/solver.lisp b/AoC2022/18/solver.lisp index 05c0102..00df016 100644 --- a/AoC2022/18/solver.lisp +++ b/AoC2022/18/solver.lisp @@ -15,6 +15,50 @@ (mapcar #'parse-integer (uiop:split-string l :separator ","))) (uiop:read-file-lines filename))) +(defun bounding-corner (points edge) + (reduce (lambda (edges point) + (mapcar edge edges point)) + points)) + +(defun box-surface (min-point max-point) + (* 2 + (loop for (a . rest) on (mapcar #'- max-point min-point) + sum (loop for b in rest + sum (* a b))))) + +(defconstant +neighbor-dirs+ '((1 0 0) (0 1 0) (0 0 1) + (-1 0 0) (0 -1 0) (0 0 -1))) + +(defun spread-steam (next outer-region cubes min-point max-point) + (loop for dir in +neighbor-dirs+ + for nbg = (mapcar #'+ next dir) + when (and (every #'<= min-point nbg max-point) + (not (member nbg cubes :test #'equal)) + (not (member nbg outer-region :test #'equal))) + collect nbg)) + +(defun fill-outside (queue outer-region cubes min-point max-point) + (reduce (lambda (out voxel) + (let ((next-queue (spread-steam voxel out cubes min-point max-point))) + (fill-outside next-queue + (append next-queue out) + cubes min-point max-point))) + queue + :initial-value outer-region)) + +(defun exterior-surface (cubes) + (let* ((min (mapcar #'1- (bounding-corner cubes #'min))) + (max (mapcar #'1+ (bounding-corner cubes #'max))) + (outer (list min))) + (- (surface + (fill-outside outer outer cubes min max)) + (box-surface min (mapcar #'1+ max))))) + + (fiveam:test solutions + ;; part 1 (fiveam:is (= 64 (surface (parse-coords "eg-in")))) - (fiveam:is (= 4474 (surface (parse-coords "input"))))) + (fiveam:is (= 4474 (surface (parse-coords "input")))) + ;; part 2 + (fiveam:is (= 58 (exterior-surface (parse-coords "eg-in")))) + (fiveam:is (= 2518 (exterior-surface (parse-coords "input"))))) |