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-rw-r--r--AoC2023/day19/solver.lisp37
1 files changed, 21 insertions, 16 deletions
diff --git a/AoC2023/day19/solver.lisp b/AoC2023/day19/solver.lisp
index 7a95a71..cc24f59 100644
--- a/AoC2023/day19/solver.lisp
+++ b/AoC2023/day19/solver.lisp
@@ -17,6 +17,11 @@
:a (copy-tree a)
:s (copy-tree s))))
+(defun update-part (range-part slot val)
+ (let ((new (copy-part range-part)))
+ (setf (slot-value new slot) val)
+ new))
+
(defun part-options (range-part)
(reduce #'* '(x m a s)
:key (lambda (v)
@@ -93,22 +98,22 @@
(if (member start '(A R))
(list start range)
(destructuring-bind (df . opts) (gethash start workflows)
- (let ((drops (loop for (op prop val target) in opts
- append
- (destructuring-bind (st . end) (slot-value range prop)
- (if (eq '< op)
- (cond ((< end val) (part-2 workflows target (copy-part range)))
- ((<= val st) nil)
- (t (let ((lf (copy-part range)))
- (setf (slot-value lf prop) (cons st (1- val))
- (slot-value range prop) (cons val end))
- (part-2 workflows target lf))))
- (cond ((> st val) (part-2 workflows target (copy-part range)))
- ((>= val end) nil)
- (t (let ((rt (copy-part range)))
- (setf (slot-value range prop) (cons st val)
- (slot-value rt prop) (cons (1+ val) end))
- (part-2 workflows target rt)))))))))
+ (let ((drops
+ (loop for (op prop val target) in opts
+ append
+ (destructuring-bind (st . end) (slot-value range prop)
+ (part-2 workflows target
+ (if (eq '< op)
+ (if (< end val)
+ (copy-part range)
+ (progn
+ (setf (slot-value range prop) (cons val end))
+ (update-part range prop (cons st (1- val)))))
+ (if (> st val)
+ (copy-part range)
+ (progn
+ (setf (slot-value range prop) (cons st val))
+ (update-part range prop (cons (1+ val) end))))))))))
(append (part-2 workflows df range) drops)))))